Material erosion monitoring system and method

Abstract

Disclosed is an improved system and method to evaluate the status of a material. The system and method are operative to identify flaws and measure the erosion profile and thickness of different materials, including refractory materials, using electromagnetic waves. The system is designed to reduce a plurality of reflections, associated with the propagation of electromagnetic waves launched into the material under evaluation, by a sufficient extent so as to enable detection of electromagnetic waves of interest reflected from remote discontinuities of the material. Furthermore, the system and method utilize a configuration and signal processing techniques that reduce clutter and enable the isolation of electromagnetic waves of interest. Moreover, the launcher is impedance matched to the material under evaluation, and the feeding mechanism is designed to mitigate multiple reflection effects to further suppress clutter.

Description

<DP=1>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²MATERIAL EROSION MONITORING SYSTEM AND METHOD²FIELD OF THE INVENTION²The present invention relates to systems and methods for evaluating the status²of a material. More particularly, the present invention relates to systems and ²methods²for determining refractory bricks- material interface using electromagnetic ²waves.²BACKGROUND OF THE INVENTION² Evaluation methods and systems exist within various industries for measuring²the properties during and after formation of certain materials. The surface ²characteristics, internal homogeneity, and thickness of a material are some of ²the ²important attributes that may require evaluation. In particular, the wall ²thickness of ²glass and plastic containers using non-contact reflective and / or absorptive ²techniques²by deploying sensors and emitters to direct radiation towards the container ²have been²addressed in the prior art, as described in U.S. Pat. App. No. 20130268237 by ²Wolfe ²et al. However, these methods are primarily aimed to evaluate the thickness of ²²manufactured glass and plastic containers by means of using radiation capable ²to pass ²through those materials without sustaining significant losses in the levels of ²such²radiation or accessing more than just one external surface of such materials.²On a bigger scale, some industries such as the glass, steel, and plastic ²industries use large furnaces to melt the raw material used for processing. ²These ²furnaces may reach a length equivalent to the height of a 20-story building. ²Thus, they ²are a key asset for manufacturers in terms of costs and operational ²functionality. In²1²<DP=2>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²order to minimize the internal heat loss at high operating temperatures, these ²furnaces ²are constructed using refractory material, having very high melting ²temperatures and ²good insulation properties, to create a refractory melting chamber. However, ²the inner ²walls of the refractory chamber of the furnace will degrade during operation. ²The²effects of this degradation include inner surface erosion, stress cracks, and ²refractory²material diffusion into the molten material.²Currently, there is no well-established method of deterministically measuring ²the thickness and erosion profile of the walls of such furnaces. As a result, ²manufacturers experience either an unexpected leakage of molten material ²through the²furnace wall or conservatively shut down the furnace for re-build to reduce ²the²likelihood of any potential leakage, based on the manufacturer's experience of ²the ²expected lifetime of the furnace. The lifetime of a furnace is affected by a ²number of ²factors, including the operational age, the average temperature of operation, ²the ²heating and cooling temperature rates, the range of temperatures of operation, ²the²number of cycles of operation, and the type and quality of the refractory ²material as²well as the load and type of the molten material used in the furnace. Each of ²these ²factors is subject to uncertainties that make it difficult to create accurate ²estimates of ²the expected lifetime of a furnace. Moreover, the flow of molten material, ²such as ²molten glass, at high temperatures erodes and degrades the inner surface of ²the²refractory material and creates a high risk for molten glass leakage through ²the²refractory wall. A major leak of molten glass through the gaps and cracks in ²the ²furnace walls may require at least 30 days of production disruption before the ²furnace ²can be restored to operating mode because it needs to be cooled down, ²repaired, and ²fired up again. Furthermore, a leak of molten glass may cause significant ²damage to²2²<DP=3>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²the equipment around the furnace and, most importantly, put at risk the health ²and life ²of workers. For these reasons, in most cases furnace overhauls are conducted ²at a ²substantially earlier time than needed. This leads to significant costs for ²manufacturers in terms of their initial investment and the reduced production ²capacity² over the operational life of the furnace.²Another important issue is that the material used to build the refractory ²chamber of the furnace may have internal flaws not visible by surface ²inspection. This ²could translate into a shorter life of the furnace and pose serious risks ²during furnace ²operation. Accordingly, on the one hand the refractory material manufacturer ²would²like to have a means to evaluate the material during manufacture to be able to ²qualify²the material for furnace construction following quality standards to deliver ²material ²with no flaws. On the other hand, the customer purchasing the refractory ²material ²would like to have a means for performing internal inspections of such ²material ²before constructing a furnace.² Previous efforts have been made to use microwave signals to measure the²thickness of materials such as furnace walls, as described in U.S. Pat. No. ²6,198,293 ²to Woskov et al. and U.S. Pat. App. No. 20130144554 by Walton et al. However, ²these efforts have faced certain challenges and limitations. In particular, ²attempts ²made to determine furnace wall thickness on hot furnaces have been generally²unsuccessful because of the large signal losses involved in evaluating the ²inner²surface of refractory materials, especially at relatively high frequency ²bands. ²Likewise, at relatively low frequency bands signals still experience losses ²and are ²limited in terms of the bandwidth and resolution required by existing systems. ²²Moreover, in placing system components close to the surface of the refractory²3²<DP=4>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²material to be evaluated, spurious signal reflections make it difficult to ²isolate the ²reflected signal of interest, thus further complicating the evaluation of the ²status of ²either the inner surface or the interior of such materials. A major challenge ²is that ²furnace walls become more electrically conductive as temperature increases.²Therefore, signals going through a hot furnace wall experience significant ²losses²making the detection of these signals very challenging.²Thus, there remains a need in the art for systems and methods capable of ²remotely evaluating the status of such refractory materials, through ²measurements of ²propagating electromagnetic waves, that avoid the problems of prior art ²systems and² methods.²SUMMARY OF THE INVENTION²An improved system and method to evaluate the status of a material is²disclosed herein. One or more aspects of exemplary embodiments provide ²advantages²while avoiding disadvantages of the prior art. The system and method are ²operative to²identify flaws and measure the erosion profile and thickness of different ²materials, ²including refractory materials, using electromagnetic waves. The system is ²designed ²to reduce a plurality of reflections associated with the propagation of ²electromagnetic ²waves launched into the material under evaluation, by a sufficient extent so ²as to².. enable detection of electromagnetic waves of interest reflected from remote²discontinuities of the material. Furthermore, the system and method utilize a ²configuration and signal processing techniques that reduce clutter and enable ²the ²isolation of electromagnetic waves of interest. Moreover, the launcher used in ²the ²system is impedance matched to the material under evaluation, and the feeding²4²<DP=5>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²mechanism is designed to mitigate multiple reflection effects to further ²suppress ²clutter.²The system launches electromagnetic waves into a near surface of a material ²to be evaluated. The electromagnetic waves penetrate the material and reflect ²from²discontinuities inside and from both the near and a remote surface of the ²material. The²reflected electromagnetic waves are received by a computer-based processor and ²²timed, using as reference the wave reflected from the near surface of the ²material. The ²computer-based processor determines the delay in time between the reference ²wave ²and other reflected electromagnetic waves, which include undesired clutter. ²Where the²to magnitude of the clutter is below the magnitude of the electromagnetic ²waves²reflected from remote discontinuities of the material, the computer-based ²processor ²identifies a peak level of magnitude associated with these discontinuities and ²²determines the distance from such discontinuities to the near surface of the ²material ²associated with the reference wave. One or more evaluations over an area of ²the²material provides the thickness of the material and the location of flaws ²inside the²material at each evaluation to create an erosion profile of the remote surface ²of the ²material.²The system also includes an electromagnetic wave launcher designed and ²adapted to reduce a plurality of reflections that significantly contribute to ²the clutter²received by the computer-based processor. The launcher provides levels of ²clutter²reduction by a sufficient extent so as to enable detection of electromagnetic ²waves of ²interest that otherwise might not be possible. The launcher may be used in ²evaluation ²of the refractory walls of hot furnaces to create an erosion profile of the ²surface of the ²inner walls in an operational furnace.²5²<DP=6>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²The method to evaluate the status and measure the erosion profile and ²thickness of different materials includes the step of setting up the ²electromagnetic ²wave launcher conformally contiguous to the near, outer surface of the ²material under ²evaluation. The method further includes the steps of launching electromagnetic ²waves²into the material and measuring, over a frequency band, the amplitude and the ²phase²of waves reflecting from discontinuities from said material. The method also ²includes ²transforming measured data to time domain, calibrating the data to distance ²domain, ²and identifying data associated with reflected electromagnetic waves of ²interest; in ²particular, waves reflected from the inner, remote surface of the material ²under² evaluation to determine the thickness of such material.²By significantly reducing the level of clutter caused by reflections and ²ringing ²of propagating electromagnetic waves, as compared to standard techniques, and ²by ²determining the location of remote discontinuities from the material under ²evaluation, ²the system and method are able to identify flaws and measure the erosion ²profile of²the remote surface of such material.²BRIEF DESCRIPTION OF THE DRAWINGS²The numerous advantages of the present invention may be better understood²by those skilled in the art by reference to the accompanying drawings in ²which:² Fig 1 shows a schematic view of an exemplary embodiment of a system using²a rolled-edge electromagnetic wave launcher.²Figs 2A to 2D show various aspects of an electromagnetic wave launcher with ²two rolled edges in accordance with one embodiment.²Fig 3 shows a design of a feeding transitioning section.²6²<DP=7>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²Fig 4 shows a plot of the magnitude of the noise, clutter, and reflected ²electromagnetic waves of interest in accordance with a hypothetical scenario.²Fig 5 shows a plot of the magnitude of the noise, clutter, and reflected ²electromagnetic waves of interest using a launcher with and without rolled ²edges.² Fig 6 shows a perspective view of a planar electromagnetic wave launcher in²accordance with another embodiment.²Fig 7 shows a perspective view of a planar electromagnetic wave launcher²with curved edges in accordance with another embodiment.²Fig 8 shows a schematic view of a method for computing the thickness of a² dielectric material according to any of the embodiments of the invention.²Fig 9 shows a perspective view of an electrically-small electromagnetic wave²launcher in accordance with an embodiment of the invention.²DETAILED DESCRIPTION OF THE INVENTION² The following description is of a particular embodiment of the invention, set²out to enable one to practice an implementation of the invention, and is not ²intended ²to limit the preferred embodiment, but to serve as a particular example ²thereof. Those ²skilled in the art should appreciate that they may readily use the conception ²and ²specific embodiments disclosed as a basis for modifying or designing other ²methods²and systems for carrying out the same purposes of the present invention. Those²skilled in the art should also realize that such equivalent assemblies do not ²depart ²from the spirit and scope of the invention in its broadest form.²In accordance with certain aspects of an embodiment of the invention, a ²material evaluation system is shown in Fig 1. The system is configured to ²evaluate a²7²<DP=8>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²status of a refractory material used as a furnace wall. Thus, the refractory ²material has ²an outer surface and an inner surface opposite the outer surface. The inner ²surface of ²the refractory material is contiguous to (i.e., in contact with) a molten ²material, such ²as glass, plastic or steel or any other material contained within the furnace. ²An²electromagnetic (EM) wave launcher 10, comprising a feeding end 12, a ²launching²end 14, and an elongated section 16 in between and adjoining feeding end 12 ²and ²launching end 14, is disposed contiguous to an area of the outer surface of ²the ²refractory material to be evaluated. EM wave launcher 10 is designed to ²operate at a ²frequency band large enough to cover the operational frequency band of the ²system.²1() Specifically, and as discussed in greater detail below, the dimensions ²of the²rectangular cross section (width and height) at the launching end of EM wave ²launcher 10, the length of the launcher (or alternatively the width and height ²flare ²angles and the length), and the dielectric properties of the material ²occupying the ²internal volume of EM wave launcher 10 are all selected to cause EM wave ²launcher²10 to operate at a sufficiently large frequency band to cover the operational ²frequency²band of the system, and with regard to certain aspects of an embodiment of the ²²invention, in the frequency band from 0.5 GHz to 10 GHz. Likewise, EM wave ²launcher 10 is designed to tolerate the required temperature range of the ²near, outer ²surface of a furnace wall. More particularly, the material that is used to ²form EM²wave launcher 10 is selected to allow EM wave launcher 10 to withstand such ²high²temperatures (the area of the launcher exposed to the highest temperature ²being the ²area placed contiguous to the furnace outer surface). For example, the ²conductive ²material on the sides and on the rolled edges of the launcher is selected so ²as to have a ²melting temperature point larger (including some appropriate safety margin as ²may be²8²<DP=9>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²selected by those skilled in the art) than the temperature of the furnace ²outer surface. ²Likewise, with regard to the dielectric material occupying the internal volume ²of the ²launcher as discussed in greater detail below, typical ceramic-type materials ²withstand ²temperatures much higher than the maximum expected temperature of the furnace².. outer surface. With regard to certain aspects of an embodiment of the ²invention, the²dielectric substrate material also has similar properties to those of the ²ceramic ²material, in terms of temperature of operation. Finally, in the case that a ²variable ²conductivity material is used (again as discussed in greater detail below), ²the ²protecting layers of adhesive provide temperature isolation to the variable²1() .. conductivity material. Preferably, the selection of such materials will ²allow use of the²EM wave launcher 10 against a surface having a temperature as high as 1600 F ²for a ²few seconds, which is sufficient enough to take the necessary data for ²operation. ²However, for longer duration operation, such materials should be able to ²withstand an ²ambient temperature limit of approximately 700 F, with the surface reaching² .. temperatures up to approximately 1000 F.²As used herein, "near" surface is also intended to refer to the outer surface ²of ²the material under evaluation that is contiguous to launching end 14 of EM ²wave ²launcher 10. Likewise, "remote" surface is also intended to refer to the inner ²surface ²of the material under evaluation opposite the near surface immediately ²adjacent².. launching end 14 of EM wave launcher 10. Thus, in the case of a furnace, ²the remote²surface comprises the inner surface of the outer wall of the furnace, and the ²near ²surface comprises the outer surface of the outer wall of the furnace.²Feeding end 12 includes a feeding transition section 18 electrically connected ²²to a radiofrequency (RF) transmission line, such as a coaxial cable 20. A ²computer-²9²<DP=10>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²based processor 22 is also electrically connected to coaxial cable 20. ²Accordingly, ²coaxial cable 20 is electrically connected at a first end to computer-based ²processor ²22, and at a second end to feeding transition section 18. Coaxial cable 20 is ²selected to ²have a physical length from computer-based processor 22 to feeding transition ²section²18, such that a propagation time of an EM wave propagating between first end ²and²second end of coaxial cable 20 is larger than a propagation time of the EM ²wave from ²feeding transition section 18 to the remote inner surface of the refractory ²material ²under evaluation and back to the near, outer surface of the material. In other ²words, ²the propagation time of the EM wave propagating throughout the length of ²coaxial².. cable 20 is larger than the propagation time of the EM wave propagating ²throughout²EM wave launcher 10 plus the propagation time of the EM wave propagating back ²and forth through the thickness of the refractory material.²Computer-based processor 22 comprises an RF subsystem 23, a signal ²processing subsystem, and executable computer code or software. RF subsystem ²23²comprises a tunable signal source, such as a voltage controlled oscillator or ²a²frequency synthesizer, preferably operable in a frequency band going somewhere ²²from 0.25 GHz to 30 GHz; at least one directional coupler; a coherent ²detector; and at ²least one analog-to-digital converter. The signal processing subsystem ²comprises data ²storage and data processing algorithms. Referring again to FIG. 1, it is noted ²that² components of computer-based processor 22 have not been shown as these ²components are not critical to the explanation of this embodiment. Those of ²ordinary ²skill in the art will realize that various arrangements of RF subsystem 23 ²components ²may be possible and additional components, such as filters, impedance matching ²²networks, amplifiers, non-coherent detectors and other test instrumentation ²may be²<DP=11>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²used as different ways to implement RF subsystem 23 functions of computer-²based ²processor 22 as are known in the prior art.²Launching end 14 of EM wave launcher 10 is placed in physical contact with ²the refractory material to be evaluated. More specifically, launching end 14 ²is².. preferred to be physically conformal to the area of the near surface of the ²refractory²material with which launching end 14 is in physical contact (i.e., is ²configured so as to ²minimize spacing between launching end 14 and the surface under examination). ²In ²other words, it is not desired to have any gap or clearance larger than 2 mm ²between ²the surface of launching end 14 and the area of the near surface of the ²refractory² 1() material with which launching end 14 is in physical contact.²Elongated section 16 of EM wave launcher 10 is preferably selected to have a ²physical length from feeding end 12 to launching end 14 such that a ²propagation time ²of an EM wave propagating from feeding end 12 to launching end 14 is larger ²than a ²propagation time of said EM wave propagating from the near, outer surface of ²the²refractory material under evaluation to the remote, inner surface of the ²material. In²other words, the propagation time of the EM wave propagating along the EM wave ²²launcher 10 is preferred to be larger than the propagation time of the EM wave ²²propagating through the thickness of the refractory material. Typical ²thickness values ²of refractory material of furnace walls range from 0.5 inches to 12 inches.²Accordingly, depending on the target range of thickness measurements, the ²length of²elongated section 16 of EM wave launcher 10 typically ranges somewhere from 2 ²inches to 15 inches.²Figs 2A to 2D show various aspects of one version of EM wave launcher 10, ²used in Fig 1. In this embodiment, Fig 2A illustrates a perspective view of EM ²wave²11²<DP=12>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²launcher 10, physically structured as a truncated, two-edge flared pyramid ²with a ²rectangular cross-section from feeding end 12 to launching end 16. Figs 2B and ²2C ²show side views of EM wave launcher 10 having rectangular cross-section ²dimensions of 0.2 inches x 0.13 inches at feeding end 12 and 2.5 inches x 4.25 ²inches²at launching end 14. Accordingly, four side plates 24a, 24b, 24c, and 24d form ²EM²wave launcher 10. Each side plate 24a, 24b, 24c, and 24d is preferably made of ²a ²dielectric or conductive material. Typically, a conductive material having a ²thickness ²in the range of 0.01 inches and 0.25 inches, and more preferably between 0.05 ²inches ²and 0.1 inches is used. In the particular embodiment shown in Fig 2D, a ²conductive²material approximately 0.078-inches thick was used. Thus, more specifically, ²side²plates 24a, 24b, 24c, and 24d of EM wave launcher 10 form a structure that ²surrounds, without fully enclosing, an internal volume of EM wave launcher 10. ²Side ²plates 24a, 24b, 24c, and 24d of EM wave launcher 10 do not surround the ²internal ²volume at feeding end 12 and launching end 14 of EM wave launcher 10.² Referring again to Fig 2A, at any cross-sectional view, four edges 26a, 26b,²26c, and 26d form the rectangular cross section of EM wave launcher 10. The ²dimensions of such rectangular cross-section of EM wave launcher 10 linearly ²increase from feeding end 12 to transition points 28a, 28b, 28c and 28d, which ²are ²located along elongated section 16 in between feeding end 12 and launching end ²14.²Accordingly, the shape of EM wave launcher 10, from feeding end 10 to ²transition²points 28a, 28b, 28c, and 28d, corresponds to the shape of a regular ²rectangular cross-²section pyramid. However, from transition points 28a, 28b, 28c, and 28d to ²launching ²end 14, the dimension of each end of opposite edges 26a and 26c of the ²rectangular ²cross-section of EM wave launcher 10 increases following a curve described by ²a²12²<DP=13>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²circular function with a 0.78 inches radius of curvature, as shown in Fig 2D. ²More ²specifically, the structure of EM wave launcher 10 corresponds to the ²structure of a ²truncated rectangular cross-section pyramid having two elliptically-flared or ²elliptically-rolled opposite edges. Typical values of a thickness of launching ²end 14²may range between 0 and 0.25 inches. In this particular embodiment, launching ²end²14 has a thickness of 0.078 inches. Likewise, the rolling of edges 26a and 26c ²starts at ²a point where a separation between transition points 28a and 28b or ²equivalently ²between transition points 28c and 28d is 2.9 inches. Accordingly, transition ²points ²28a, 28b, 28c, and 28d are located approximately 0.63 inches from launching ²end 14.² Furthermore, EM wave launcher 10 is physically configured to have an²impedance at launching end 14 that substantially matches an impedance of the ²near ²surface of the refractory material. The internal volume of EM wave launcher 10 ²may ²be at least partially filled with a solid ceramic filling material having an ²impedance ²that substantially matches a predetermined impedance of the refractory ²material under²the normal operating conditions of the furnace. This predetermination may be²obtained by measuring the dielectric properties of the refractory material at ²various ²temperatures using methods well known in the prior art. Alternatively, the ²manufacturer of the refractory material may provide data about the dielectric ²properties of the material at different temperatures. These data can be used ²to²determine the impedance of the material. The impedance of the refractory ²material is²primarily determined by both a relative dielectric permittivity of the ²material and a ²tangent loss of the material. Typically, the relative dielectric permittivity ²may range ²from 1 to 25 depending on the specific type of material and temperature of the ²²material. Thus, the internal volume of EM wave launcher 10 may be partially or²13²<DP=14>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²completely filled with a dielectric filling material of similar relative ²dielectric ²permittivity to that of the refractory material to substantially match the ²impedance of ²the refractory material.²The filling material used to fill the internal volume of EM wave launcher 10²may be air, liquid or solid. Preferably the filling material is a mixture of ²solid powder²or granulated material in which the maximum dimension of each grain is desired ²to be ²no larger than ten percent of a wavelength of an EM wave propagating in EM ²wave ²launcher 10 at the lowest frequency of operation. More preferably, the filling ²material ²is a solid ceramic piece of material or the like adapted to fit into the ²internal volume²of EM wave launcher 10. Alternatively, the internal volume of EM wave launcher ²10²may be layered, from feeding end 12 to launching end 14, so that each layer is ²filled ²with a filling material that has a slightly different dielectric permittivity ²to the ²dielectric permittivity of the filling material of any adjacent layer to ²structure multiple ²layers of different dielectric permittivity in an arrangement that gradually ²adjust an²impedance from feeding end 12 to the impedance of the refractory material to ²be²evaluated at launching end 14. Whenever necessary a lid or cap may be placed ²at ²feeding end 12 and launching end 14 to prevent the filling material from ²exiting the ²internal volume of EM wave launcher 10 during manipulation or operation of EM ²wave launcher 10. Those skilled in the art realize that a cap placed at ²launching end²14 must be made of a material having similar dielectric characteristics as ²those as the²filling material to prevent a substantial discontinuity to an EM wave ²propagating ²through said cap. Likewise, a cap placed at feeding end 12 must be made of a ²material ²according to a specific design of feeding transition section 18.²14²<DP=15>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²Fig 3 shows a design of a feeding transitioning section 18 using a cap 30 ²formed by a shell of a conductive material having a thickness of approximately ²0.1 ²inches. Cap 30 forms an air-filled cavity surrounded by the shell, having a ²semicircular cross-section in a first dimension, and a rectangular cross-²section in a² second dimension normal to said first dimension. In this embodiment, the²semicircular cross-section is defined by a semicircular section 32, having an ²internal ²radius of approximately 0.75 inches, and a linear section of approximately 1.6 ²inches, ²comprising a first section 34a and a second section 34b of substantially the ²same ²dimensions, separated by a gap 35, whereas said rectangular cross-section is ²defined²by said linear section, defining a width of approximately 1.6 inches, and ²another²linear section, defining a length of approximately 1.3 inches (not shown in ²Fig 3). ²Cap 30 has a first circular opening at one side of semicircular section 32 ²large ²enough to just allow coaxial cable 20 to enter inside of the cavity. Outer ²conductor 36 ²of coaxial cable 20 is electrically connected to both semicircular section 32 ²of cap 30².. and conductive side plate 24a of EM wave launcher 10 at feeding end 12. A ²pin or²probe 38 is formed by extending a center conductor of coaxial cable 20 beyond ²outer ²conductor 36 of coaxial cable 20 inside of the cavity; in this case the pin ²length is ²approximately 0.1 inches. Likewise, gap 35 of cap 30 defines a second opening ²that ²separates linear section 34a from linear section 34b. The dimensions of gap 35 ²are²large enough just to allow the tip of the truncated end of EM wave launcher ²10, that is²closer to feeding end 12, to fit into the cavity. In this embodiment, side ²plates 24a and ²24c of EM wave launcher 10 are made of conductive material. Accordingly, side ²plate ²24a of EM wave launcher 10 is electrically connected to second section 34b, ²and side ²plate 24c of EM wave launcher 10 is electrically connected to first section ²34a. Also,²<DP=16>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²outer conductor 36 of coaxial cable 20 is electrically connected to first ²section 34a. ²Additionally, pin 38 is electrically connected to second section 34b. In this ²way, EM ²wave launcher 10 may be excited by pin 38 of coaxial cable 20 in a cavity-²backed ²feeding pin configuration. Typically, pin 38 is located at a distance from the ²cap equal²to a quarter wavelength corresponding to a center frequency of the frequency ²band of²the EM waves propagating along EM wave launcher 10.²Those skilled in the art will realize that semicircular section 32 may be ²shaped ²following different configurations, such as elliptical, planar or other smooth ²function. ²Likewise, one or more sections of cap 30 may be removed in certain ²configurations,²and the cavity may be filled with dielectric material. Furthermore, the ²dimensions of²linear sections 34a and 34b may be designed in combination with feeding end 12 ²of²EM wave launcher 10 to reduce undesirable ringing effects.²Operation²In accordance with further aspects of an embodiment of the invention, the²manner of using the material evaluation system of Fig 1 is based on the ²fundamentals²of EM wave propagation. Computer-based processor 22 controls the tunable RF ²signal source, operating in a frequency band that properly penetrates the ²refractory ²material with low enough loss, preferably somewhere between 0.25 GHz and 30 ²GHz, ²and more preferably operating in a frequency range somewhere between 0.25 GHz²and 10 GHz. The RF signal source is carried by coaxial cable 20 to feeding ²transition²section 18 in order to excite at least one propagation mode within EM wave ²launcher ²10 such that a number of EM waves are able to propagate from feeding end 12 to ²²launching end 14 at the frequency range of interest. The bandwidth of the EM ²waves²16²<DP=17>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²propagating in EM wave launcher 10 is typically selected to be at least 2 GHz ²to ²permit the resolution required by the user.²Upon reaching EM wave launcher 10, the RF signal source from computer-²based processor 22 will experience an initial discontinuity at feeding ²transition section²18 resulting from adapting EM fields of the RF signal source propagating along²coaxial cable 20 to EM fields of propagating modes excited inside EM launcher ²10. ²This initial discontinuity causes a part of the RF signal source to reflect ²back to ²computer processor 22.²Additionally, once EM waves propagating along EM wave launcher 10 reach²the near, outer surface of the refractory material, a first part of the EM ²waves will²penetrate through the near, outer surface of the material and propagate inside ²the ²material until reaching the remote, inner surface of the material. A second ²part of the ²EM waves will reflect back, from the near, outer surface of the refractory ²material, to ²EM wave launcher 10 and a part of the reflected EM waves will propagate until²reaching computer processor 22. Upon the first part of the EM waves reaching ²the²remote, inner surface of the refractory material, a third part of the EM waves ²will ²penetrate through and propagate inside the molten material contained within ²the ²furnace. A fourth part of the EM waves will reflect back, from the remote, ²inner ²surface of the refractory material, to EM wave launcher 10 and a part of the ²reflected²EM waves will propagate until reaching computer processor 22. The second part ²of²the EM waves reflect as a result of the waves propagating through a media ²discontinuity between internal volume of EM wave launcher 10 at launching end ²14 ²and the refractory material. Likewise, the fourth part of the EM waves reflect ²as a²17²<DP=18>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²result of the waves propagating through a media discontinuity between the ²refractory ²material and the molten material.²Furthermore, EM waves propagating through the refractory material may ²experience discontinuities resulting from a presence of an inhomogeneous ²region or a²flaw inside the refractory material. As such, a part of the EM waves will ²reflect back,²from the flaw inside the refractory material, to EM wave launcher 10 and a ²part of the ²reflected EM waves will propagate until reaching computer processor 22.²Even further, EM waves propagating along EM wave launcher 10 will ²experience an additional edge discontinuity at launching end 14. More ²specifically,²the edge discontinuity will occur at edges 26a, 26b, 26c, and 26d ²corresponding to²launching end 14, as shown in Fig 2A, as a result of the waves propagating ²through a ²media discontinuity between the internal volume of EM wave launcher 10 at ²launching end 14 and media surrounding the edges, such as the near, outer ²surface of ²the refractory material, and the medium surrounding EM wave launcher 10, such ²as²air. Accordingly, part of the EM waves will reflect back from the edges to EM ²wave²launcher 10 and a part of the reflected EM waves will propagate until reaching ²²computer processor 22.²Moreover, the EM waves reflected from edges 26a, 26b, 26c, and 26d ²corresponding to launching end 14 may reach one or more of the other edges ²multiple²times to create an undesirable "ringing" or "reverberation" effect due to ²multiple edge²reflections of the EM waves. Eventually, part of the multiple reflected EM ²waves will ²reach computer processor 22.²Likewise, any reflected wave within EM wave launcher 10 within the ²refractory material or between feeding end 12 and computer processor 22 will ²be²18²<DP=19>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²affected by any discontinuity at the near, outer surface of the refractory ²material, ²launching end 14, and feeding end 12. In other words, the effects of a ²discontinuity ²will affect propagating EM waves regardless of the direction of propagation of ²the ²EM waves, either from computer processor 22 to the remote, inner wall of the²refractory material or from the remote, inner wall of the refractory material ²to²computer processor 22. Accordingly, multiple EM wave reflections occur that ²may ²create ringing effects and adversely affect an ability of computer processor ²22 to ²detect a reflected EM wave of interest. In other words, a number of spurious ²signals ²or undesired EM wave reflections are inherently present that may cause serious²performance issues of the material evaluation system. A term commonly used to ²refer²to the aggregated effects of such spurious signals or undesired EM wave ²reflections is ²"clutter."²In particular, a first EM wave of interest to evaluate the status of the ²refractory ²material is an initial reflected EM wave from the discontinuity between ²launching end²14 and the near, outer wall of the refractory material to establish a ²reference for²determining the thickness of the refractory material or determining the ²location of a ²flaw inside said material. A second EM wave of interest is an initial ²reflected EM ²wave from the discontinuity between the remote, inner wall of the refractory ²material ²and the molten material within the furnace to determine the thickness of the ²refractory² material. A third EM wave of interest is an initial reflected EM wave from a ²discontinuity of a flaw inside the refractory material to determine the ²location of the ²flaw.²Correspondingly, a number of different terms are major contributors to the ²overall clutter in the system. A first term corresponds to the reflected RF ²signal from²19²<DP=20>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²feeding transition section 18 to computer-based processor 22. A second term ²corresponds to the multiple RF signal reflections or ringing between feeding ²transition ²section 18 and computer-based processor 22. A third term corresponds to the ²reflected ²EM wave from edges 26a, 26b, 26c, and 26d at launching end 14 to computer-²based²processor 22. A fourth term corresponds to the multiple edge reflections or ²ringing of²EM waves from edges 26a, 26b, 26c, and 26d at launching end 14 to computer-²based ²processor 22. A fifth term corresponds to the multiple reflections or ringing ²of EM ²waves between the near, outer wall of the refractory material and the remote, ²inner ²wall of the refractory material that reach computer-based processor 22. A ²sixth term²1() .. corresponds to the multiple reflections or ringing of EM waves between ²a flaw inside²the refractory material and the near, outer wall of the refractory material ²that reach ²computer-based processor 22. A seventh term corresponds to the multiple ²reflections ²or ringing of EM waves between a flaw inside the refractory material and the ²remote, ²inner wall of the refractory material that reach computer-based processor 22. ²An².. eighth term corresponds to the multiple reflections or ringing of EM waves ²between²feeding end 12 and the near, outer wall of the refractory material that reach ²computer-²based processor 22. A ninth term corresponds to the multiple reflections or ²ringing of ²EM waves between feeding transition section 18 and feeding end 12 that reach ²computer-based processor 22.² In this embodiment, an RF signal or EM wave that is received by computer-²based processor 22 goes through a coherent detector that provides voltages ²proportional to the in-phase (I) and quadrature-phase (Q) components of the ²received ²RF signal or EM wave relative to a reference version of the original RF signal ²source; ²thus permitting both amplitude and relative phase to be measured. The ²reference²<DP=21>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²version of the original RF signal source is provided by a sample obtained by ²means of ²a directional coupler. Analog-to-digital converters output digital data ²proportional to ²the I voltage and the Q voltage outputs of the coherent detector. The digital ²data is ²then read, stored, and processed by computer-based processor 22. Optionally,².. computer-based processor 22 further adapts the processed data to display ²the results to²the user. Computer-based processor 22 has executable computer code configured ²to ²measure reflected EM waves received to produce frequency domain data and ²transform the frequency domain data to time domain data. Furthermore, computer-²²based processor 22 calibrates the time domain data to distance domain data, ²identifies².. a peak in the distance domain profile associated with an EM wave of ²interest reflected²from the refractory material, and determines a distance traveled by the EM ²wave of ²interest.²Thus, computer-based processor 22 is capable of determining a relative time ²delay between a received RF signal or EM wave and the original RF signal ²source.²The time domain data can be used to determine the relative time of arrival of ²each EM²wave of interest and the clutter terms. Of particular importance is that any ²EM wave ²of interest will be received during an interval of time between the arrival of ²the first ²EM wave of interest, used as a reference, and the arrival of the second EM ²wave of ²interest. In other words, any information of the status of the refractory ²material will²arrive to computer-based processor 22 during this interval of time. ²Accordingly, the²only clutter terms that may arrive during this interval of time at computer-²based ²processor are those corresponding to the second, third, fourth, sixth, eighth, ²and ninth ²clutter terms.²21²<DP=22>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²Furthermore, by selecting the length of coaxial cable 20 such that the ²propagation time of an EM wave propagating throughout the length of coaxial ²cable ²20 is larger than the propagation time of the EM wave propagating throughout ²EM ²wave launcher 10 plus the propagation time of the EM wave propagating back and²forth through the thickness of the refractory material, the multiple ²reflections²corresponding to the second clutter term will arrive at computer-based ²processor 22 ²later than any EM wave of interest. Likewise, by selecting the length of ²elongated ²section 16 of EM wave launcher 10 such that the propagation time of an EM wave ²²propagating along EM wave launcher 10 is larger than the propagation time of ²the EM²wave propagating through the thickness of the refractory material, the ²multiple²reflections corresponding to the eighth clutter term will arrive at computer-²based ²processor 22 later than any EM wave of interest.²The ringing effects produced by the sixth clutter term, i.e., the ringing of ²EM ²waves between a flaw inside the refractory material and the near, outer wall ²of the²refractory material that reach computer-based processor 22, will arrive at ²computer-²based processor 22 at the same interval time as the EM waves of interest only ²if the ²flaw is located closer to the near, outer wall of the refractory material than ²to the ²remote, inner wall of the material. However, this effect will be noticeable ²only when a ²flaw is present at a distance from the near, outer wall of the material that ²is smaller²than half of the thickness of the material. Those skilled in the art will ²realize that²measurements at multiple frequencies and known signal processing techniques ²may ²allow determining when this situation occurs.²As shown in Fig 3, the use of a cavity-backed feeding transitioning in this ²embodiment may reduce the effects of the ninth clutter term, i.e., the ringing ²of EM²22²<DP=23>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²waves between feeding transition section 18 and feeding end 12 that may reach ²computer-based processor 22 during the same time interval as an EM wave of ²interest. ²Because of the inherent wideband requirement of EM wave launcher 10, the ²critical ²quarter-wavelength distance is difficult to maintain over the whole frequency ²band of²operation. Accordingly, the ringing effects may partly, although still ²significantly, be²removed.²Therefore, the most relevant and at the same time the most difficult clutter ²terms to remove from the system are those related to edges 26a, 26b, 26c, and ²26d at²launching end 14. These are the third and fourth clutter terms as described ²above.² The computer executable code of computer-based processor 22 allows²calibration of the time domain data to a distance domain data based upon a ²known ²velocity of an EM wave travelling along coaxial cable 20 and EM wave launcher ²10 ²and through the refractory material under evaluation. Also, the reference or ²zero ²distance value corresponds to the transition between launching end 14 of EM ²wave²launcher 14 and the near, outer surface of the refractory material. Fig 4 ²shows a plot²of the magnitude of the received EM waves at computer-based processor 22 as a ²function of distance. This represents a possible scenario for the system shown ²in Fig ²1, wherein a flaw within the refractory material is present. The effect of the ²clutter ²terms in determining the EM waves of interest at computer-based processor 22 ²may²be noticed. The solid line curve represents the magnitude of the EM waves of ²interest²plus the system noise. The dashed line curve represents the magnitude of the ²clutter ²plus the system noise. Note also that the distance interval of interest is ²only the ²distance corresponding to the thickness of the refractory material, in this ²case ²approximately 6 inches. Where the magnitude of the clutter plus noise is about ²the²23²<DP=24>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²same or larger than the magnitude of the EM waves of interest associated with ²both ²the flaw and the thickness of the refractory material, as shown in Fig 4, ²those EM ²waves of interest cannot be detected by computer-based processor 22. Thus, ²neither ²the EM wave of interest associated with the flaw of the refractory material, ²showed².. approximately at a distance of 4 inches in Fig 4, nor the EM wave of ²interest²associated with the remote, inner wall of said material, showed approximately ²at a ²distance of 6 inches, can be detected due to the clutter effects. Accordingly, ²the ²thickness of the refractory material cannot be determined. In this case, only ²the ²magnitude of the EM wave of interest associated with the near, outer surface ²of the²refractory material can be determined because it is above the magnitude of the ²clutter²plus noise. However, determining the magnitude of only the EM wave of interest ²²associated with the near, outer surface of the material is not very useful.²Hence, it is of utmost importance to reduce the magnitude of the clutter plus ²noise to a level below the magnitude of the EM waves of interest associated ²with the²flaw or the thickness of the refractory material to be able to determine the ²status of the²material. Typically, in most applications involving the evaluation of a ²refractory ²material, the clutter is so large that a material evaluation system becomes ²unreliable ²and, in general, unable to determine the status of the material. In addition, ²known ²techniques such as those based on subtraction of measurements of reflected EM²waves taken at different locations on the surface of the furnace wall are ²ineffective to²reduce the clutter. The reason for the ineffectiveness of the techniques is ²the ²variability of the clutter component associated with each of the measurements, ²caused ²by variations of the surface temperature, tangent loss, and set up of EM wave ²launcher ²10 and the surface of the furnace wall, from measurement to measurement.²24²<DP=25>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²Figs 1 and 2 show a design of EM wave launcher 10 that significantly reduces ²the clutter terms related to edges 26a, 26b, 26c, and 26d at launching end 14. ²As ²previously indicated, the clutter terms related to edges 26a, 26b, 26c, and ²26d at ²launching end 14 are the most relevant and at the same time the most ²challenging²clutter terms to suppress from the system. Fig 5 shows actual measurement data ²of a²10-inches thick refractory material installed on an operating furnace. In this ²case, the ²thickness of the refractory wall was selected to be free of flaws and be so ²thick that ²there are no reflected EM waves from flaws and the reflected EM waves from the ²²remote, inner surface of the furnace wall are so attenuated that they do not ²reach²computer-based processor 22. Thus, Fig 5 shows only results of clutter plus ²noise²measurements for an EM wave launcher 10 with rolled edges and a substantially ²similar EM wave launcher 10 with no rolled edges. A solid line curve ²represents the ²magnitude of clutter plus noise of the processed time domain data using an EM ²wave ²launcher 10 with rolled edges, as described above. The dashed line curve ²represents²the magnitude of clutter plus noise where a substantially similar EM wave ²launcher²10 without rolled edges is used. As seen in Fig 4, an effect of using an EM ²wave ²launcher with rolled edges is a reduction in clutter plus noise of around 20 ²to over 30 ²dB in a region where the reflected EM wave of interest associated with the ²near, outer ²surface of the furnace wall would be expected to appear, such as the region ²where² time is larger than 1 nanosecond.²Another effect of using an EM wave launcher with rolled edges is a reduction ²in clutter plus noise of as much as 10 dB for the reflected EM wave of ²interest ²associated with the near, outer surface of the furnace wall. Also, because the ²system ²noise is substantially similar in both cases, when using EM wave launcher 10 ²with²<DP=26>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²and without rolled edges, the reductions in clutter plus noise levels observed ²in Fig 5 ²correspond primarily to reductions in clutter levels.²With regard to Fig 1, in which a single EM wave launcher 10 is used, such a ²system is commonly referred to as a mono-static configuration. Optionally, an²additional EM wave launcher 10 may be added to only receive reflected EM ²waves.²In such configuration, commonly known as a bi-static configuration, a first ²"active" ²EM wave launcher 10 will be used to launch the EM waves into the material ²under ²evaluation as shown in Fig 1. A second "passive" EM wave launcher 10 is placed ²next ²to the first EM wave launcher 10. The second EM wave launcher 10 will only ²receive² reflected EM waves. Thus, the reflected EM waves return to computer-based ²processor 22 using a different path from the path used by the launched EM ²waves. ²This provides an inherent separation between launched and received EM waves. ²Unlike Fig 1, this bi-static configuration does not require an additional ²component, ²such as a directional coupler, to separate transmitted and received EM waves ²coming².. from and going to computer-based processor 22 to perform a coherent ²detection of the²reflected EM waves.²Preferably, in a bi-static configuration, a center point of an imaginary plane ²²containing launching end 14 of the first EM wave launcher 10 is placed as ²close as ²possible to a corresponding center point of a plane containing launching end ²14 of the² second EM wave launcher 10, having both launching ends conformally placed in ²contact with the near, outer surface of the refractory material. One reason ²for a ²preferred minimum separation between EM wave launchers in this configuration ²is ²that the distance traveled by the reflected EM waves is shorter, which results ²in less ²losses. A second reason is that the second EM wave launcher will be able to ²receive²26²<DP=27>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²more reflected EM waves, especially those EM waves reflected at angles near ²180 ²degrees with respect to the launched EM waves. Furthermore, to receive the ²reflected ²EM waves having a substantially same electric field polarization as an ²electric field ²polarization of the launched EM waves, in certain situations, an orientation ²of the²first EM wave launcher 10 with respect to the second EM wave launcher 10 may ²be²selected to have edges 24a, 24b, 24c, and 24d at launching end 14 of the first ²EM ²wave launcher 10 be substantially parallel to edges 24a, 24b, 24c, and 24d at ²launching end 14 of the second EM wave launcher 10. Those skilled in the art ²will ²recognize that a relative orientation of the first EM wave launcher 10 with ²respect to²the second EM wave launcher 10 may need to be adjusted to receive the ²reflected EM²waves having a substantially desired electric field polarization ¨ such as co-²polarized, ²cross-polarized, or any combination thereof ¨ as compared to an electric field ²²polarization of the launched EM waves. Furthermore, the second EM wave ²launcher ²is not required to be identical or similar to the first EM wave launcher.²With regard to still further aspects of the invention, where transverse ²electric²and magnetic (TEM) waves are exclusively used, EM wave launcher 10 may be ²configured to have only two opposite side plates made of conductive material. ²In ²other words, in a first configuration only side plates 24a and 24c are made ²using a ²conductive material. In a second configuration, only side plates 24b and 24d ²are made² using a conductive material. The preferred thickness dimensions for these two²different configurations are the same as for the configuration having four ²conductive ²side plates, as shown in Fig 2. Thus, more specifically, a first group of two ²opposite ²side plates of EM wave launcher 10 are made of conductive material, and a ²second ²group of two opposite side plates may be removed, be made of a dielectric or ²other²27²<DP=28>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²material as known in the prior art, or simply be replaced by opposite surfaces ²of a ²solid filling dielectric material such as ceramic.²Further, EM wave launcher 10 may alternatively be provided at least two ²opposite side plates in which a material having a variable conductivity is ²disposed,²instead of being made using a conductive material. Those skilled in the art ²will realize²that one or more coating applications of a conductive material applied to a ²dielectric ²material filling the internal volume of EM wave launcher 10 may be used to ²achieve a ²desired profile of variable conductivity along the side plates. Alternatively, ²a film, ²uniform in thickness and having a variable conductivity may be disposed ²between²feeding end 12 and launching end 14. More specifically, the variable ²conductivity²material may be disposed on at least side plates 24a and 24c or at least side ²plates 24b ²and 24d. In this alternative embodiment, the internal volume of EM wave ²launcher 10 ²is filled with a solid dielectric, preferably ceramic. A variable conductive ²film is ²disposed on two opposite side surfaces of the dielectric, going from feeding ²end 12 to² launching end 14, to form side plates 24a and 24c or 24b and 24d of EM wave²launcher 10. In this configuration, a first end of the variable conductivity ²material is ²disposed closer to feeding end 12, and a second end of the variable ²conductivity ²material is disposed closer to launching end 14. Thus, electromagnetic waves ²propagate in EM wave launcher 10 within a region partly surrounded by the ²variable²conductivity material, wherein the conductivity varies as a function of the ²distance²from a point on the variable conductivity material to launching end 14. ²Alternatively, ²multiple sections of conductive films, each having a different conductivity, ²may be ²arranged sequentially from lower to higher conductivity to create an ²increasing ²conductivity profile as a function of distance from the first to the last of ²the sections.²28²<DP=29>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²The thickness of each individual layer of conductive film is preferred to be ²in the ²range of between 0.001 inches and 0.1 inches.²Typically, a sheet resistance characterizes the degree of conductivity of a ²thin ²film layer of material of uniform thickness. A larger sheet resistance ²corresponds to a²lower conductivity and vice versa. In the configuration described immediately ²above,²the sheet resistance of the variable conductivity material increases following ²an ²exponential function from the first end of the variable conductivity material, ²closer to ²feeding end 12, to the second end of the variable conductivity material, ²closer to ²launching end 14.²In particular, the lowest value of sheet resistance of the variable ²conductivity²material at the first end, closer to feeding end 12, is preferred to be below ²1 Ohm per ²square. More preferably, the lowest value of sheet resistance is similar to ²the sheet ²resistance of a conductive material such as copper or silver. On the other ²hand, the ²highest value of sheet resistance of the variable conductivity material at the ²second²end, closer to launching end 14, is preferred to be in a range somewhere ²between 50²Ohms per square and 1000 Ohms per square. More preferably, the lowest value of ²²sheet resistance is similar to the sheet resistance of a dielectric material ²such as ²ceramic. In other words, the variable conductivity material behaves as a ²conductive ²material closer to feeding end 12 and gradually transitions to have the ²preferred²maximum sheet resistance value as the variable conductivity material gets ²closer to²launching end 14. This variable conductivity profile provides a significant ²reduction ²of reflections of EM waves from the edges at launching end 14. Accordingly, ²the ²variable conductivity profile provides a significant reduction of clutter ²resulting from ²EM waves reflecting from the edges at launching end 14.²29²<DP=30>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²The above described variable conductivity profile is substantially the same ²for ²each of at least two opposite side plates 24a and 24c or 24b and 24d of EM ²wave ²launcher 10. However, those skilled in the art will realize that different ²profiles in ²each side plate may be used. In general, the profile of the sheet resistance ²of the²variable conductivity material may increase following a step, elliptical, ²exponential,²or a smooth transitioning function, or any combination thereof, optimally ²designed to ²reduce the clutter, from the first end of the variable conductivity material, ²closer to ²feeding end 12, to the second end of the variable conductivity material, ²closer to ²launching end 14.²A critical issue in using a resistive film disposed relatively close to ²launching²end 14 is that, under normal operating conditions, the refractory material may ²reach ²temperatures of several hundred degrees Fahrenheit at the near, outer surface ²of the ²furnace. Launching end 14 is in physical contact with the hot material. Hence, ²most ²likely, the film may be physically damaged unless protected. A conductive film ²may²be sandwiched in between two layers of high-temperature adhesive to protect ²the film.²This three-layer structure may be disposed on at least two opposite side ²surfaces of a ²dielectric material filling the internal volume of EM wave launcher 10, going ²from ²feeding end 12 to launching end 14, to form side plates 24a and 24c of EM wave ²²launcher 10. In the present embodiment, the dielectric material and the three-²layer²structure was cured at a temperature of approximately 300 degrees Fahrenheit ²for a 2-²hour period. Preferably, the film and each of the layers of adhesive has a ²thickness ²ranging somewhere between 0.001 inches and 0.01 inches.²More preferably, the layers of adhesive have similar electrical properties as ²the ²electrical properties of the dielectric material. Furthermore, high-²temperature ceramic²<DP=31>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²cement or other equivalent material may be placed on top of the three-layer ²structure ²for increased protection. In this manner, a compact packaging is provided to ²not only ²protect the film from physical damage due to the high temperatures experienced ²by ²launching end 14 and from manipulation during set up and operation of EM wave²launcher 10, but also to hold the film in place during operation. Those ²skilled in the²art will realize that various types of adhesives and cement materials ²commercially ²available may be used, typically having a curing time between one hour and ²three ²hours at temperatures ranging from 200 to 500 degrees Fahrenheit.²The effects of configuring EM wave launcher 10 using a variable conductivity²material as described are so significant in reducing clutter terms related to ²the edges²of the launching end 14 of EM wave launcher 10 that an embodiment using the ²variable conductivity material may not require flared or rolled edges at ²launching end ²14. Thus, either a first configuration using an EM launcher with rolled edges ²or a ²second configuration using an EM wave launcher having at least two side plates ²with².. a variable conductivity material may be used to significantly reduce edge ²reflections²in most applications. Of course, a third configuration combining both ²techniques to ²reduce edge reflections will provide further improvement to the material ²evaluation ²system.²Launching end 14 of EM launcher 10 may extend following a topology of the²near, outer surface of the material to be evaluated. Alternatively, the rolled ²edges of²launching end 14 of EM wave launcher 10 may follow a circular function or ²other ²function that smoothly extends away sufficiently enough from transition points ²28a, ²28b, 28c, and 28d so as to reduce the effects of edge reflections.²31²<DP=32>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²Optionally, the entire material evaluation system may be packaged into a ²single portable unit in which an operator triggers the launch of EM waves, ²over a ²frequency band, by activating a switch. More specifically, the entire material ²²evaluation system may be enclosed in a single hand held unit. The unit may ²evaluate²the status of the furnace wall at a single point and record the information in ²a built-in²memory. Alternatively, the EM wave launcher along with a subset of components ²of ²the material evaluation system may be integrated into a single assembly to ²launch the ²EM waves and to only measure, record, and store the amplitude and phase of the ²EM ²waves coming into the EM wave launcher. Then the stored data may be ²transferred to²computer-based processor 22 using a portable memory drive or by means of a ²flexible²cable for evaluating the status, or ultimately determining the thickness, of ²the subject ²material under evaluation. Alternatively, the data may be transferred ²wirelessly in real ²time or at a convenient opportunity. Furthermore, the hand held unit may ²include data ²processing components and a display to show the thickness of the furnace wall ²and / or²the distance from the outer, near surface of the refractory material to a ²discontinuity²embedded in the material under evaluation. The portable unit may be designed ²to scan ²by hand an area of the furnace wall while taking measurements at multiple ²locations. ²Moreover, EM wave launcher 10 may be periodically used for one or more ²evaluations of said material under evaluation, or may be installed permanently ²and²fixed onto the outer, near surface of the material under evaluation to ²continuously²monitor the status of the material under evaluation. Alternatively, a region ²of the ²outer, near surface of the material under evaluation may be scanned, by moving ²the ²EM wave launcher, during operation, over and while maintaining physical ²contact ²with the outer, near surface of the material under evaluation.²32²<DP=33>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²The RF front-end of RF subsystem 23 of computer-based processor 22 may be ²integrated with feeding transition section 18 of EM wave launcher 10. In other ²words, ²coaxial cable 20 may be removed from the system as it is no longer required. ²In this ²situation, any multiple reflections between the RF front-end and feeding ²transition².. section 18 will arrive to computer-based processor 22 before any of the ²reflected EM²waves of interest. Alternatively, coaxial cable 20 may be disposed following a ²²predetermined physical route to produce maximum stability of the RF signal or ²the ²EM wave travelling in the cable. Furthermore, such stability may be ²accomplished by ²mechanically attaching the cable to a supporting structure, so as to minimize ²any²movement of coaxial cable 20. Likewise, preventing coaxial cable 20 from ²following²a route requiring the cable to bend beyond a certain angle from a straight-²line routing ²may help in reducing the overall clutter in the system.²Those skilled in the art will recognize that EM wave launcher 10 may be ²implemented using multiple devices and materials in various configurations ²that²include one or more of an antenna, a waveguide, a dielectric material, a ²conductive²material, a material having a variable conductivity, a metamaterial, or any ²combination thereof configured in different geometrical arrangements.²In particular, Fig 6 shows an optional configuration of a planar EM wave ²launcher 60 comprising a bow-tie antenna having a first layer 62a of ²conductive²material and a second layer 62b of conductive material, wherein the edges of ²both of²layers 62a and 62b are linearly tapered to have a triangular shape and are ²disposed on ²a top surface of dielectric substrate 64. EM wave launcher 60 is typically fed ²by a ²balanced-to-unbalanced device, referred to as a "balun," that adapts an ²impedance of ²an unbalanced transmission line, such as a coaxial cable, to an input ²impedance of the²33²<DP=34>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²bow-tie antenna. In this configuration, the input impedance of the bow-tie ²antenna is ²substantially matched to the impedance of the near, outer surface of the ²refractory ²material. Substrate 64 has an underside surface, with a layer of conductive ²material ²disposed over all of the underside surface to form a ground plane, and two ²openings to²allow the balun to feed the bow-tie antenna. Typically, these openings are ²made²through the smallest dimension or thickness of substrate 64 and are large ²enough to ²just allow a wire to go through each opening and electrically connect the ²balun to ²each layer 62a and 62b at points where the layers are at its closest distance, ²²approximately 0.1 inches in this case, as it is well understood by those ²skilled in the²art. In this configuration, the dimensions of substrate 64 are 4 inches long, ²3 inches²wide, and 0.27 inches thick. A maximum width of each layer 62a, 62b is ²approximately 2.7 inches, and a length of approximately 1.95 inches. The ²thickness of ²each layer 62a, 62b is typical of those previously described corresponding to ²a film or ²coating of conductive material applied to a dielectric substrate. ²Additionally, substrate²64 may have a dielectric permittivity somewhere between 1 and 150, and a ²tangent²loss between 0 and 1.²In a typical evaluation of a material, the top surface of substrate 64, ²containing ²the bow-tie antenna, is conformally placed against the near, outer surface of ²the ²refractory material to launch EM waves, coming from computer-based processor ²22,²into the refractory wall and to receive reflected EM waves going back to ²computer-²based processor 22. Those skill in the art will realize that layers 62a and ²62b can be ²implemented by means of a variable conductivity material as described in ²previous ²embodiments of EM wave launcher 10. Likewise, the shape of layers 62a and 62b ²can²34²<DP=35>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²be other than triangular, having straight edges, curved edges that follow a ²particular ²function, or a combination thereof.²Similarly, Fig 7 shows a configuration for planar EM wave launcher 60 of Fig ²6, having substrate 64 consisting of a first planar section 64a, a first ²curved-edge²section 64b, a second curved-edge section 64c, a second planar section 64d, ²and a²third planar section 64e. First planar section 64a extends over a plane from ²the bow-²tie feeding area in a first dimension along the width of substrate 64 until ²reaching the ²width of substrate 64, in this case approximately 3 inches, and in a second ²dimension ²along the length of substrate 64 until reaching transition points 66a, 66b, ²66c, and²66d; in this case, the distance between transition points 66a and 66b and ²between²transition points 66c and 66d is approximately 4 inches.²As the first curved-edge section 64b and the second curved-edge section 64c ²extend away from the feeding point of the bow-tie antenna along the length of ²substrate 64, sections 64b and 64c bend towards the underside surface of ²substrate 64²following a circular path with a radius of curvature of approximately 1.6 ²inches for a²quarter of circumference to reach transition points 68a, 68b, 68c, and 68d. In ²other ²words, the distance along the curved path of substrate 64 between transition ²points ²66a and 68a is approximately 2.51 inches. This is substantially the same ²distance ²between transition points 66b and 68b, transition points 66c and 68c, and ²transition²points 66d and 68d, respectively. Likewise, this is the same length of section ²64b and²section 64c along the curved path of substrate 64. At transition points 68a ²and 68c, ²second planar section 64d begins to extend the length of substrate 64 by ²approximately 0.5 inches. Correspondingly, at transition points 68b and 68d, ²third ²planar section 64e begins to extend the length of substrate 64 by ²approximately 0.5²<DP=36>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²inches. As such, second planar section 64d, and a third planar section 64e are ²²substantially perpendicular to first planar section 64a.²In the configurations shown in Figs 6 and 7, the strongest clutter terms ²correspond to multiple reflections at the edges of the bow-tie antenna. The ²dimensions² of the curved edges of the configuration of Fig 7 are selected to extend the²propagation time of the EM wave propagating on the surface of substrate 64 ²such that ²the time is longer than the propagation time of an EM wave propagating from ²the ²near, outer surface of the refractory wall to the remote, inner surface of the ²refractory ²wall. In this manner, the clutter effects associated with the multiple ²reflections of EM²waves from the edges of the bow-tie antenna are significantly reduced. Those ²skilled²in the art will realize that, in the configuration of Fig 7, the edges of ²layers 64b and²64c may be tapered to follow an elliptical function, an exponential function, ²a smooth ²transitioning function, or any combination thereof. In addition, the length of ²sections²64d and 64e may be adjusted with the ultimate goal of reducing the clutter.² Furthermore, in each of the above-described configurations, a person of²ordinary skill in the art will realize that a particular single signal ²processing method ²may be selected according to an estimated thickness of the material to be ²evaluated. ²For example, a signal processing method based on a Fourier Transform may be ²used ²to process the data received by computer-based processor 22, especially ²related to the²evaluation of walls with thickness larger than 6 inches. On the other hand, ²signal²processing methods based on super resolution algorithms would be preferred for ²²evaluation of walls with thickness below 3 inches. Alternatively, a hybrid ²signal ²processing method comprised of one or more single signal processing methods ²may ²be used according to additional factors including the frequency of operation ²and²36²<DP=37>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²bandwidth of the system, the temperature of operation of the furnace, and the ²type and ²quality of the refractory material.²Likewise, in each of the above-described configurations, the launching end of ²EM wave launcher 10 is, as discussed elsewhere in this specification, ²impedance²matched to the material under evaluation, which further helps to suppress ²clutter.²Regarding each of the above-described configurations, a method depicted in ²Fig 8 for determining the thickness of the subject material under evaluation, ²such as ²refractory material, may be performed according to the following:²1. At step 810, setting up an EM wave launcher by placing a launching².. end of the EM wave launcher conformally contiguous to an outer, near ²surface of the²material under evaluation to maximize physical contact, which corresponds to ²minimizing gaps, between the launching end of the EM wave launcher and the ²outer, ²near surface of the material under evaluation, such that upon operation of the ²EM ²launcher, EM waves are launched into the outer, near surface of the material ²under² evaluation.²2. Next, at step 820, launching EM waves from the EM launcher into the ²outer surface of the material under evaluation by exciting EM wave propagating ²²modes inside the EM wave launcher over a transmit frequency range, and ²correspondingly generating EM waves propagating inside the EM wave launcher ²from²a feeding end of the EM wave launcher to the launching end of the EM wave ²launcher, over said frequency range.²3. Next, at step 830, measuring the amplitude and the phase of EM waves ²coming into the EM wave launcher over the frequency range, as a result of²37²<DP=38>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²propagation of the EM waves launched by the EM wave launcher into the outer ²surface of the material under evaluation.²4. Next, at step ²840, storing the measured amplitude and phase frequency²domain data of the EM waves coming into the EM wave launcher.²5. Next, at step ²850, transferring the recorded frequency domain data to a²computer-based data processor.²6. Next, at step 860, transforming the recorded frequency domain data to ²time domain data by performing a mathematical inverse Fourier transform or ²other ²model-based inverse spectral transformation method, using the computer-based ²data² processor.²7. Next, at step 870, calibrating the time domain data to distance domain ²data, according to the known or estimated phase velocity of the EM waves in ²the ²material under evaluation, and defining a reference point in a distance domain ²profile, ²based on a peak value over a clutter plus noise level of the calibrated ²distance domain²data, that corresponds to the physical length between the feeding end of the ²EM wave²launcher and the outer, near surface of the material under evaluation; wherein ²the ²reference point may be associated with an EM wave reflected into the EM wave ²launcher from the outer, near surface of the material under evaluation.²8. Next, at step 880, evaluating the calibrated distance domain data to²identify a peak value, over the clutter plus noise level, between the ²reference point²and a known original thickness of the material under evaluation, which may be ²associated with an EM wave reflected into the EM wave launcher from the inner, ²²remote surface of the material under evaluation.²38²<DP=39>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²9. Last, ²at step 890, determining a distance from the identified peak value²at step 880 to the reference point; the distance corresponding to the ²thickness of the ²material under evaluation (distance between the outer, near surface and the ²inner, ²remote surface of the material under evaluation).²Those of ordinary skill in the art will recognize that the steps above ²indicated²can be correspondingly adjusted for specific configurations and other ²constraints such ²as measurement equipment, operating frequency band, type of EM wave launcher, ²operational conditions, surrounding environment, and available area and ²location for ²implementation of the material evaluation system for a given application. In²particular, measurements of the amplitude and the phase of EM waves, required ²over²a high dynamic range (in some cases in excess of 90 dB), may be accomplished ²in ²multiple ways, such as through use of a network analyzer, to measure the Si 1 ²scattering parameter, over a frequency band, using a monostatic configuration ²(a ²single device to both launch EM waves and receive EM waves) or to measure the ²521²scattering parameter, over a frequency band, using a bistatic configuration (a ²first²device to launch EM waves and a second device to receive EM waves).²Additionally, those skilled in the art will recognize that, while evaluating ²the ²calibrated distance domain data, intermediate peak values over the clutter ²plus noise ²level may appear between the reference point, associated with an EM wave ²reflected²from the outer, near surface of the material under evaluation, and the peak ²value²associated with an EM wave reflected from the inner, remote surface of the ²material ²under evaluation; it being understood that the intermediate peak values may be ²²associated with flaws of the material under evaluation existing between the ²outer, near²39²<DP=40>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²surface of the material under evaluation and the inner, remote surface of the ²material ²under evaluation.²Furthermore, the calibration of the time domain data to distance domain data ²includes the subtraction of the delay time (distance) associated with the EM ²wave²launcher and cables. Moreover, the frequency dispersion effects of the EM wave²launcher and the material under evaluation may be removed, if necessary, by ²normalizing the measured data of the material under evaluation with respect to ²²another set of measured data corresponding to a reference configuration, by ²way of ²non-limiting example, of a known characteristic and thickness of a material ²similar to²1() the material under evaluation, through processes well known to those ²skilled in the²art.²Still further, it is noted that the material evaluation system as described in ²Fig ²1 operates in the frequency domain by launching EM waves at specific ²frequencies ²within the frequency band of interest. Then the recorded frequency domain data ²is²transformed to time domain data for further processing. However, the system ²may be²implemented to operate in the time domain as well. Preferably, in the time ²domain ²operation mode, the EM wave launcher may launch a plurality of EM waves in the ²²frequency domain, such that the time domain representation of this plurality ²of EM ²waves corresponds to an RF waveform of short duration, for example a Gaussian,² Rayleigh, Hermitian, Laplacian pulse or of the like or a combination thereof.²Alternatively, the EM wave launcher may be directly fed with such type of ²pulse by a time domain RF waveform generator. More preferably, the duration of ²the ²RF waveform is not larger than 5 nanoseconds. Accordingly, the EM wave ²launcher ²will transmit and receive time domain pulses and the system will measure the²<DP=41>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²amplitude and time of arrival of these pulses, store the measured data, and ²transfer the ²stored data to the computer-based processing unit in the time domain. Then the ²steps ²may proceed of calibrating the time domain data to distance domain data, ²evaluating ²the calibrated domain data to identify the location of flaws on the inner, ²remote²surface of the material under evaluation, and determining the thickness of the ²material²under evaluation.²In each of the above-described configurations, as applicable, the length of ²the ²elongated section of the EM wave launcher 10, between feeding end 12 and the ²portion of the launching end farthest away from feeding end 12, is selected to ²be long²enough such that the multiple reflections corresponding to the eighth clutter ²term and²other potential multiple reflections will arrive at computer-based processor ²22 ²distinctively later than any EM wave of interest. In this situation, the ²propagation time ²of an EM wave propagating along the EM wave launcher 10 is distinguishably ²larger ²than the propagation time of the EM wave propagating through the thickness of ²the² refractory material under evaluation.²Accordingly, it is of utmost importance to configure the EM wave launcher 10 ²such that the time of receipt of an EM wave of interest, reflected from a ²remote ²discontinuity of the material under evaluation, is distinguishable from the ²time of ²receipt of spurious signals, reflected from the near surface of the material ²under²evaluation. Hence, the length of the elongated section 16 of EM wave launcher ²10,²between feeding end 12 and the portion of the launching end farthest away from ²²feeding end 12, may be shortened. The shortened length is selected to be short ²enough ²such that the multiple reflections corresponding to the eighth clutter term ²and other ²potential multiple reflections, including at least part of those corresponding ²to the²41²<DP=42>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²fourth clutter term, will arrive at the computer-based processor earlier than ²any EM ²wave of interest. In this case, the propagation time of an EM wave propagating ²along ²EM wave launcher 10 is distinguishably shorter than the propagation time of ²both the ²EM wave propagating through the thickness of the refractory material under² evaluation and multiple reflections from the launching end 14.²Fig 9 shows a perspective view of an electrically-small EM wave launcher 90, ²comprising a feeding end 92 and a launching end 94. In particular, the length ²between ²feeding end 92 and launching end 94 is electrically small enough such that ²multiple ²EM wave reflections between launching end 94 and feeding end 92 arrive at a ²time²distinguishably earlier than the time of arrival of any EM wave of interest. ²Likewise,²multiple EM wave reflections from the near, outer wall of the refractory ²material ²under evaluation (not shown) will arrive at a time distinguishably earlier ²than the time ²of arrival of any EM wave of interest.²Feeding end 92 includes a feeding transition section 96 that electrically²connects to a radiofrequency (RF) transmission line (not shown) through a ²coaxial²connector 98. In this configuration, feeding transition section 96 consists of ²a coaxial ²cable-fed cavity-backed feed. In particular, feeding transition section 96 is ²formed by ²an air-filled box of conductive material having rectangular cross-sections ²along each ²dimension of the box. The design characteristics of feeding transition section ²96,²corresponding to a coaxial cable-fed cavity-backed feed with rectangular cross-²²sections, are well-known in the prior art and are equivalent to those of ²feeding ²transition section 18, as described above in reference to Fig 3. Those skilled ²in the art ²will realize that the RF transmission line electrically connected to feeding ²transition ²section 96 may comprise a coaxial cable, a coplanar waveguide, a stripline or ²a²42²<DP=43>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²microstrip. In an alternative configuration a coplanar waveguide is configured ²to ²impedance-match and directly connect to at least one component of an RF ²transmitter ²or an RF receiver.²Accordingly, EM wave launcher 90 may be used in place of EM wave²launcher 10 as indicated in the above-described embodiments, as applicable. ²More²specifically, in this embodiment, EM wave launcher 90 consists of a modified ²pyramidal horn antenna with a rectangular cross section. EM wave launcher 90 ²structurally comprises a first flared plate 91a and a second flared plate 91b ²disposed ²opposite to plate 91a, like in a standard pyramidal horn antenna, having a ²rectangular²cross section, in which two opposite smaller plates are removed. In this ²configuration,²first and second flared plates 91a, 91b are made of a conductive material.²The thickness of first and second flared plates 91a, 91b at launching end 94 ²defines a first edge 93a and a second edge 93b each of which may range in ²length ²from 0.01 to 1 inch. Importantly, prior art EM wave launchers, such as ²standard horn².. antennas, have a typical thickness-to-length ratio of the flared plates in ²the order of²less than 5%. However, in a preferred configuration, the thickness of first ²and second ²flared plates 91a, 91b is uniform, the thickness-to-length ratio of flared ²plates 91a, ²91b is in the range of 15% to 85%, and the length of each edge 93a, 93b is at ²least ²0.25 inch to smoothen the discontinuity experienced by an EM wave propagating² .. along EM wave launcher and reaching a third edge 93c at launching end 94.²More preferably, one or more edges of first and second flared plates 91a, 91b ²at launching end 94 may be rolled following an elliptical function or other ²smooth ²function to reduce the effects of edge reflections, for example, as described ²above in ²reference to Figs 1 and 2A-2D. Most preferably, at least a portion of one or ²more of²43²<DP=44>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²edges of first and second flared plates 91a, 91b at launching end 94, ²including edges ²93a, 93b, or corresponding edges adjacent or opposite to edges 93a, 93b, have ²a ²rolled configuration.²Alternatively, the thickness of first and second flared plates 91a, 91b need ²not² be uniform from feeding end 92 to launching end 94 and may have a variable ²thickness profile. In the case where the thickness of first and second flared ²plates 91a, ²91b is variable, a preferred thickness profile may include a gradually ²increasing ²thickness at each of first and second flared plates 91a, 91b, having the ²thickest portion ²at edges 93a, 93b of launching end 94. Furthermore, first and second flared ²plates 91a,²91b of EM wave launcher 90 may comprise a material having a variable ²conductivity ²instead of being made of a conductive material, as described above in ²reference to ²Figs 2A-2D.²In the particular configuration shown in Fig 9, the volumetric region wherein ²the EM waves propagate within the EM wave launcher, in between first and ²second²flared plates 91a, 91b, from feeding end 92 to launching end 94 is filled with ²a ²dielectric material 95, which may be a gas, liquid, or solid. Preferably, ²dielectric ²material 95 is a solid material having an impedance that substantially matches ²a ²predetermined impedance of the refractory material under the normal operating ²conditions of the furnace, as explained in the above-described embodiments,² particularly in reference to Figs 2A-2D.²More preferably, the volumetric region defined by dielectric material 95 is ²larger than the above-referenced volumetric region wherein the EM waves ²propagate ²within the EM wave launcher, such that a portion 95a of dielectric material 95 ²and a ²corresponding identical opposite portion (not shown) at least partly protrude ²only²44²<DP=45>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²from the sides of first and second flared plates 91a, 91b going along from ²feeding end ²92 to launching end 94. Accordingly, an edge 95b of dielectric material 95 is ²aligned ²with edges 93a and 93b, such that the side of EM wave launcher 90, at ²launching end ²94, and edges 93a, 93b, 93c, and 95b all lie in the same plane. Most ²preferably,²portion 95a of dielectric material 95 and the corresponding identical opposite ²portion²(not shown) of dielectric material 95 symmetrically protrude on the sides of ²EM wave ²launcher 90 from feeding end 92 to launching end 94, each having the shape of ²a ²wedge with a thick end at feeding end 92 of at least 0.05 inch. This ²configuration of ²dielectric material 95 contributes to the mitigation of both multiple EM wave²1() ²reflections from the edges of flared plates 91a, 91b and coupling to and from ²external²devices and other components.²Those skilled in the art will recognize that dielectric material 95, portion ²95a, ²and the corresponding identical opposite portion (not shown) may each comprise ²²different shapes, sizes, and types of materials.² Preferably, EM wave launcher 90 is designed to operate in the frequency²range from 0.25 GHz to 6 GHz. As a result, the dimensions of the rectangular ²cross ²section (width and height) at launching end 94 of EM wave launcher 90, the ²length of ²EM wave launcher 90, and the dielectric properties of dielectric material 95 ²are all ²selected to enable EM wave launcher 90 to operate within this frequency range ²as²well known in the prior art. In addition, EM wave launcher 90 is designed to ²tolerate²the required operating temperature range of the near, outer surface of a ²furnace wall. ²Optionally, EM wave launcher 90 can be used standalone (mono-static) or in ²array of more than one unit (multi-static) configuration, as described above ²in ²reference to Fig 1 and well known in the prior art. Likewise, EM wave launcher ²90²<DP=46>²CA 03043161 2019-05-07²WO 2018 / 089044 ²PCT / US2017 / 029309²may be part of an entire material evaluation system packaged into a single ²portable ²unit, a single hand held unit, or integrated into a single assembly as ²described above. ²In general, the various above-described configurations and method may be ²implemented to collect measurement data directly as part of a time domain-²based² material evaluation system. Accordingly, one or more time-domain pulses are²transmitted and the corresponding reflected pulses are recorded for data ²processing ²and material evaluation. In particular, and with reference to Fig 9, EM wave ²launcher ²90 may be implemented to operate in a time domain-based material evaluation ²system. In this case, the length of flared plates 91a, 91b is preferably ²dimensioned²such that the propagation time of a transmitted pulse from feeding end 92 to ²launching²end 94 of EM wave launcher 90 is less than 1 nanosecond.²The various embodiments have been described herein in an illustrative ²manner, and it is to be understood that the terminology used is intended to be ²in the ²nature of words of description rather than of limitation. Any embodiment ²herein²disclosed may include one or more aspects of the other embodiments. The ²exemplary²embodiments were described to explain some of the principles of the present ²invention so that others skilled in the art may practice the invention. ²Obviously, many ²modifications and variations of the invention are possible in light of the ²above ²teachings. The present invention may be practiced otherwise than as ²specifically²described within the scope of the appended claims and their legal equivalents.²46²

Claims

<DP=1>²CLAIMS²We claim:²1. A system for evaluating a status of a material, comprising:²a. an electromagnetic wave launcher having a first feeding end and a second ²launching end, wherein said first feeding end includes a feeding mechanism to ²excite ²an electromagnetic wave able to propagate through said electromagnetic wave ²launcher, wherein said second launching end is physically structured to reduce ²a ²plurality of reflections and probe ringing of said electromagnetic wave ²propagating ²through said launching end, by a sufficient extent so as to enable detection ²of an ²electromagnetic wave of interest reflected from a remote discontinuity of said ²²material, wherein said electromagnetic wave launcher is provided a physical ²configuration to have an impedance at said second launching end that ²substantially ²matches an impedance of a near surface of said material, wherein said ²electromagnetic wave launcher is adapted to enable receipt of said ²electromagnetic ²wave of interest reflected from said remote discontinuity of said material ²within a ²time period sufficient to distinguish between said reflected electromagnetic ²wave of ²interest and reflected spurious signals from said near surface of said ²material, and ²wherein said launching end is adapted to be conformal to an area of said near ²surface ²of said material; and²b. a computer-based processor having an executable computer code ²configured to: measure said reflected electromagnetic wave of interest to ²produce ²frequency domain data; transform said frequency domain data to time domain ²data; ²calibrate said time domain data to distance domain data; identify a peak in ²said²²47²<DP=2>²distance domain profile associated with said electromagnetic wave of interest ²reflected from said material; and determine a distance traveled by said ²electromagnetic wave of interest reflected from said material.²2. The system of claim 1, said electromagnetic wave launcher further ²comprising a ²pyramidal horn antenna having a rectangular cross-section and comprising a ²first ²flared plate having a planar section and two flared sections along opposite ²side edges ²of said planar section of said first flared plate, and a second flared plate ²positioned ²opposite said first flared plate, said second flared plate comprising a planar ²section ²and two flared sections along opposite side edges of said planar section of ²said second ²flared plate.²3. The system of claim 2, wherein a thickness of at least one of said first ²flared plate ²and said second flared plate is variable.²4. The system of claim 2, wherein a thickness-to-length ratio of at least one ²of said ²first flared plate and said second flared plate is within the range of 15% to ²85%.²5. The system of claim 2, wherein at least a portion of a volumetric region, ²between ²said first flared plate and said second flared plate, comprises a dielectric ²material, ²which extends beyond said two flared sections along said opposite side edges ²of said ²planar section of at least one of said first flared plate and said second ²flared plate.²²48²<DP=3>²6. The system of claim 1, wherein calibrating said time domain data to a ²distance ²domain data is performed by said computer executable code based upon a known ²velocity of a said electromagnetic wave of interest travelling through said ²material.²7. The system of claim 1, wherein said computer-based processor is adapted to ²visually display information about said status of said material based upon ²said ²distance traveled by said electromagnetic wave of interest reflected from said ²²material.²8. The system of claim 1, wherein said status of said material is a thickness ²of said ²material.²9. The system of claim 1, wherein said status of said material is a flaw of ²said ²material.²10. The system of claim 1, wherein said electromagnetic wave launcher and at ²least ²one other component of said system are integrated into a single unit.²11. The system of claim 1, wherein said second launching end has at least one ²edge ²physically conformed to extend away from said area to be evaluated of said ²near ²surface of said material.²12. The system of claim 11, wherein said edge has a smooth rolled-edge ²configuration.²²49²<DP=4>²13. The system of claim 1, wherein a volumetric region within said ²electromagnetic ²wave launcher in which said electromagnetic waves propagate between said ²launching ²end and said feeding end comprises a dielectric material.²14. The system of claim 1, wherein said electromagnetic wave launcher is ²formed ²using a variable conductivity material disposed between said first feeding end ²and ²said second launching end, wherein said variable conductivity material has a ²first end ²closer to said first feeding end and a second end closer to said second ²launching end, ²and wherein said conductivity increases as a function of a distance from a ²point on ²said variable conductivity material to said second end of said variable ²conductivity ²material closer to said second launching end of said electromagnetic wave ²launcher.²15. The system of claim 1, wherein said first feeding end is adapted to reduce ²a ²plurality of reflections of said excited electromagnetic wave at said first ²feeding end, ²by a sufficient extent so as to reduce a level of clutter otherwise present in ²said ²system.²16. The system of claim 15, wherein said first feeding end further comprises a ²cavity-²backed feeding pin.²17. The system of claim 1, wherein said first feeding end further comprises a ²feeding ²transition section that electrically connects a radiofrequency transmission ²line to said ²first feeding end.²²<DP=5>²18. The system of claim 17, wherein said radiofrequency transmission line is ²configured to electrically connect to at least one component selected from the ²group ²of a radiofrequency receiver and a radiofrequency transmitter.²19. The system of claim 1, said system further comprising an RF subsystem ²generating an electromagnetic wave in a frequency range of between 0.25 and 30 ²²GHz.²20. The system of claim 1, wherein said electromagnetic wave launcher is ²adapted to ²shorten receipt of said reflected spurious signals from said near surface of ²said ²material by a time period sufficient to distinguish between said reflected ²electromagnetic wave of interest and said reflected spurious signals from said ²near ²surface of said material.²21. The system of claim 1, wherein said electromagnetic wave launcher is ²adapted to ²shorten receipt of reflected electromagnetic waves from a portion of said ²electromagnetic wave launcher by a time period sufficient to distinguish ²between said ²reflected electromagnetic wave of interest and said reflected electromagnetic ²waves ²from said portion of said electromagnetic wave launcher.²22. A method for evaluating a status of a material, comprising:²a. providing an electromagnetic wave launcher having a first feeding end and ²a second launching end, wherein said first feeding end includes a feeding ²mechanism ²to excite an electromagnetic wave able to propagate through said ²electromagnetic ²wave launcher, wherein said second launching end is physically structured to ²reduce a²²51²<DP=6>²plurality of reflections of said electromagnetic wave propagating through said ²²launching end, by a sufficient extent so as to enable detection of an ²electromagnetic ²wave of interest reflected from a remote discontinuity of said material, ²wherein said ²electromagnetic wave launcher is provided a physical configuration to have an ²impedance at said second launching end that substantially matches an impedance ²of a ²near surface of said material, wherein said electromagnetic wave launcher is ²adapted ²to enable receipt of said electromagnetic wave of interest reflected from said ²remote ²discontinuity of said material within a time period sufficient to distinguish ²between ²said reflected electromagnetic wave of interest and reflected spurious signals ²from ²said near surface of said material, and wherein said launching end is adapted ²to be ²conformal to an area of said near surface of said material;²b. placing said launching end of said electromagnetic wave launcher ²conformally contiguous to said area of said near surface of said material to ²be ²evaluated;²c. launching a plurality of electromagnetic waves, propagating within a ²predetermined frequency range, onto said area to be evaluated of said near ²surface of ²said material;²d. detecting said electromagnetic wave of interest within said predetermined ²frequency range; and²e. determining said status of said material based upon a determined distance ²traveled by said electromagnetic wave of interest reflected from said remote ²discontinuity of said material.²²52²<DP=7>²23. The method of claim 22, wherein said distance traveled by said ²electromagnetic ²wave of interest is determined based upon a time of travel of said ²electromagnetic ²wave of interest.²24. The method of claim 23, wherein said time of travel of said ²electromagnetic wave ²of interest is greater than a time of travel of said spurious signals by a ²sufficient ²extent so as to enable temporal isolation of said electromagnetic wave of ²interest from ²said spurious signals.²25. The method of claim 22, wherein a time domain representation of said ²plurality ²of electromagnetic waves propagating within a predetermined frequency range ²corresponds to a radiofrequency waveform of a short pulse duration.²26. The method of claim 25, wherein said radiofrequency waveform of short ²duration ²is selected from the group of a Gaussian pulse, a Rayleigh pulse, a Hermitian ²pulse, a ²Laplacian pulse, and a combination thereof²27. The method of claim 25, wherein said duration of said radiofrequency ²waveform ²is not larger than 5 nanoseconds.²28. The method of claim 22, wherein determining said status of said material ²further ²comprises:²a. measuring a set of data in time domain pertaining to said detected ²electromagnetic wave of interest;²b. calibrating said time domain data to a distance domain data;²²53²<DP=8>²c. identifying a peak in said distance domain data associated with said ²electromagnetic wave of interest reflected from said remote discontinuity of ²said ²material;²d. determining a distance traveled by said electromagnetic wave of interest ²reflected from said remote discontinuity of said material; and²e. determining a measurement of a distance from said near surface of said ²material to said remote discontinuity of said material based upon said ²distance ²traveled by said electromagnetic wave of interest reflected from said remote ²discontinuity of said material.²29. The method of claim 28, wherein calibrating said time domain data to said ²distance domain data is performed based upon a known propagation velocity of ²said ²electromagnetic wave of interest through said material.²30. The method of claim 22, wherein determining said status of said material ²further ²comprises:²a. measuring a set of data pertaining to said detected electromagnetic wave of ²²interest;²b. providing a first means for storing said set of data;²c. providing a computer-based data processor for processing said set of data ²for evaluating said status of said material;²d. transferring said set of data from said first means to said computer-based ²data processor; and²e. processing said set of data by means of at least one signal processing ²method.²²54²<DP=9>²31. The method of claim 30, further comprising the step of processing said set ²of data ²utilizing a signal processing method selected according to a characteristic of ²said ²material to be evaluated.²32. The method of claim 22, wherein said status of said material is a ²thickness of said ²material.²33. The method of claim 22, wherein said frequency range is between 0.25 and ²30 ²GHz.²34. A method for evaluating a status of a material, comprising:²a. providing an electromagnetic wave launcher having a first feeding end and ²a second launching end, wherein said first feeding end includes a feeding ²mechanism ²to excite an electromagnetic wave able to propagate through said ²electromagnetic ²wave launcher, wherein said second launching end is physically structured to ²reduce a ²plurality of reflections of said electromagnetic wave propagating through said ²²launching end, by a sufficient extent so as to enable detection of a ²radiofrequency ²waveform of interest reflected from a remote discontinuity of said material, ²wherein ²said electromagnetic wave launcher is provided a physical configuration to ²have an ²impedance at said second launching end that substantially matches an impedance ²of a ²near surface of said material, wherein said electromagnetic wave launcher is ²adapted ²to enable receipt of said radiofrequency waveform of interest reflected from ²said ²remote discontinuity of said material within a time period sufficient to ²distinguish ²between said reflected radiofrequency waveform of interest and reflected ²spurious²²<DP=10>²signals from said near surface of said material, and wherein said launching ²end is ²adapted to be conformal to an area of said near surface of said material;²b. placing said launching end of said electromagnetic wave launcher ²conformally contiguous to said area of said near surface of said material to ²be ²evaluated;²c. transmitting said radiofrequency waveform onto said area to be evaluated ²of said near surface of said material;²d. detecting said radiofrequency waveform of interest; and²e. determining said status of said material based upon a determined distance ²traveled by said radiofrequency waveform of interest reflected from said ²remote ²discontinuity of said material.²35. The method of claim 34, wherein said radiofrequency waveform has a short ²duration and is selected from the group of a Gaussian pulse, a Rayleigh pulse, ²a ²Hermitian pulse, a Laplacian pulse, and a combination thereof.²36. The method of claim 35, wherein said duration of said radiofrequency ²waveform ²is not larger than 5 nanoseconds.²37. The method of claim 34, wherein said distance traveled by said ²radiofrequency ²waveform of interest is determined based upon a time of travel of said ²radiofrequency ²waveform of interest.²38. The method of claim 37, wherein said time of travel of said radiofrequency ²²waveform of interest is greater than a time of travel of said spurious signals ²by a²²56²<DP=11>²sufficient extent so as to enable temporal isolation of said radiofrequency ²waveform ²of interest from said spurious signals.²39. The method of claim 34, wherein determining said status of said material ²further ²comprises:²a. measuring a set of data in time domain pertaining to said detected ²radiofrequency waveform of interest;²b. calibrating said time domain data to a distance domain data;²c. identifying a peak in said distance domain data associated with said ²radiofrequency waveform of interest reflected from said remote discontinuity ²of said ²material;²d. determining a distance traveled by said radiofrequency waveform of ²interest reflected from said remote discontinuity of said material; and²e. determining a measurement of a distance from said near surface of said ²material to said remote discontinuity of said material based upon said ²distance ²traveled by said radiofrequency waveform of interest reflected from said ²remote ²discontinuity of said material.²40. The method of claim 39, wherein calibrating said time domain data to said ²distance domain data is performed based upon a known propagation velocity of ²said ²radiofrequency waveform of interest through said material.²41. The method of claim 34, wherein determining said status of said material ²further ²comprises:²²57²<DP=12>²a. measuring a set of data pertaining to said detected radiofrequency ²waveform of interest;²b. providing a first means for storing said set of data;²c. providing a computer-based data processor for processing said set of data ²for evaluating said status of said material;²d. transferring said set of data from said first means to said computer-based ²data processor; and²e. processing said set of data by means of at least one signal processing ²method.²42. The method of claim 41, further comprising the step of processing said set ²of data ²utilizing a signal processing method selected according to a characteristic of ²said ²material to be evaluated.²43. The method of claim 34, wherein said status of said material is a ²thickness of said ²material.²44. A system for evaluating a status of a material, comprising:²a. an electromagnetic wave launcher having a feeding end that includes a ²feeding mechanism to excite an electromagnetic wave, wherein said ²electromagnetic ²wave launcher launches said electromagnetic wave into a near surface of said²material, wherein said electromagnetic wave launcher is physically structured ²to ²reduce a plurality of reflections of said launched electromagnetic wave, by a ²sufficient ²extent so as to enable detection of an electromagnetic wave of interest ²reflected from ²a remote discontinuity of said material, wherein said electromagnetic wave ²launcher is²²58²<DP=13>²adapted to be conformal to an area of said near surface of said material and ²is ²provided a physical configuration to have an impedance that substantially ²matches an ²impedance of said near surface of said material, wherein said electromagnetic ²wave ²launcher is adapted to delay receipt of said electromagnetic wave of interest ²reflected ²from said remote discontinuity of said material by a time period sufficient to ²²distinguish between said reflected electromagnetic wave of interest and ²reflected ²spurious signals from said material; and²b. a computer-based processor having an executable computer code ²configured to: measure said reflected electromagnetic wave of interest to ²produce ²time domain data; calibrate said time domain data to distance domain data; ²identify a ²peak in said distance domain profile associated with said electromagnetic wave ²of ²interest reflected from said material; and determine a distance traveled by ²said ²electromagnetic wave of interest reflected from said material.²²59²