Continuous discharge monitor for directed energy borehole drilling.

Abstract

An apparatus and method are described for monitoring emissions from a borehole to determine the composition of earthen material removed from the borehole. Monitoring may be performed in real time as the borehole is deepened with a millimeter wave drilling beam. The technology can monitor the elemental composition of earthen materials (e.g., rocks, minerals, crystals, metals, etc.) in real time in a borehole created by a directed energy beam that melts and vaporizes the earthen material in its path. Continuous Emissions Monitors (CEMs) may be used in conjunction with directed energy mining of boreholes to rapidly survey the surface for precious and commercial metals.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority under 35 U.S.C. § 119(e) to U.S. patent application Ser. No. 63 / 291,744, filed December 20, 2021, entitled "Continuous Emissions Monitor for Directed-Energy Borehole Drilling," which is hereby incorporated by reference in its entirety. government support This invention was made with government support under Grant No. DE-AR0001051 awarded by the Department of Energy. The government has certain rights in this invention. [Background technology]

[0002] High-power directed energy beams at microwave or millimeter wave (MMW) frequencies can be used to drill boreholes in rock for, among other things, geothermal energy generation and mining. These drilling beams heat the rock to thousands of degrees Celsius, melting and vaporizing it. The vaporized rock can be ejected out of the borehole to the surface by high-pressure gas, which also prevents the borehole from collapsing. Summary of the Invention

[0003] This technology can monitor the elemental composition of earthen materials (e.g., rocks, minerals, crystals, metals, etc.) in real time within a borehole created by a directed energy beam that melts and vaporizes the earthen material in its path. The products / exhausts of such high-temperature drilling processes are typically at temperatures above 1000°C and can contain small particles and vapors that can be analyzed by continuous emissions monitoring (CEM). The use of CEM in combination with directed energy mining of boreholes allows for rapid surface exploration of precious and commercial metals. In one implementation, CEM for directed energy borehole penetration uses a portion of the directed energy beam to excite the extracted emissions, making elements detectable for identification at the borehole site in real time.

[0004] CEM can monitor boreholes drilled with millimeter-wave directed energy beams as follows: Exhaust gases produced by vaporizing earthen material with a millimeter-wave directed energy beam are directed into a plasma chamber. In the plasma chamber, the exhaust gases are heated to a plasma state, which excites exhaust gas components to produce optical radiation. A spectrometer, which can be periodically calibrated, takes spectroscopic measurements of the plasma emission. This spectroscopic measurement is then used to determine the composition of the exhaust gases.

[0005] A plasma can be generated in the plasma chamber by a portion of the MMW radiation associated with the MMW directed energy beam. This portion of the millimeter wave MMW radiation can be collected from reflected light of the MMW radiation traveling to or from the borehole. Directing exhaust gases produced by vaporizing the earth material with a portion of the MMW radiation into the plasma chamber can involve ejecting particles in the gas stream from the borehole to a sample tube connected to the plasma chamber.

[0006] A CEM for monitoring the composition of earth material in a borehole generated by a millimeter-wave directed energy beam can include a plasma chamber and a spectrometer. The plasma chamber contains a plasma generated by a portion of the millimeter-wave radiation used to form the directed energy beam, which heats vaporized gases and particles exhausted from the borehole. A spectrometer in electromagnetic communication with the plasma chamber measures an emission spectrum from the plasma chamber. The spectrum is indicative of the composition of the earth material extracted from the borehole.

[0007] The spectrometer may be a grating spectrometer configured to monitor at least one band having a bandwidth of 20 nm and a center wavelength in the range of 200 nm to 800 nm with a spectral resolution of 0.02 nm or better.

[0008] The CEM also includes a mirror disposed within the plasma chamber for focusing a portion of the MMW directed energy beam to a spot, and a sample tube extending into the plasma chamber for ejecting vapor and particles from the borehole into the plasma chamber near the spot. The CEM may also include a calibration chamber in fluid communication with the plasma chamber for providing a calibration sample to the plasma chamber. The CEM may further include a reflective power isolator in electromagnetic communication with the plasma chamber for coupling a portion of the MMW radiation out of the transmission line that directs the MMW radiation to the bottom of the borehole.

[0009] All combinations of the foregoing concepts and additional concepts discussed in more detail below (provided such concepts are not mutually inconsistent) are contemplated as part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter, as set forth at the end of this disclosure, are contemplated as part of the inventive subject matter disclosed herein. Terms explicitly used herein, which may be set forth in any disclosure incorporated by reference, should be given the meaning most consistent with the specific concepts disclosed herein. [Brief explanation of the drawings]

[0010] The drawings are primarily for illustrative purposes and are not intended to limit the scope of the inventive subject matter. The drawings are not necessarily to scale, and in some instances, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and / or structurally similar elements).

[0011] [Figure 1] Figure 1 shows a millimeter wave (MMW) directed energy borehole system with continuous emissions monitoring (CEM) for borehole harvest / exhaust.

[0012] [Figure 2] FIG. 2 shows a plasma chamber for exciting atomic emissions in a portion of the borehole harvest / exhaust using the power harvested from the main directed energy borehole beam in the system of FIG.

[0013] [Figure 3] FIG. 3 shows a calibration source that can be coupled to the plasma chamber of FIG.

[0014] [Figure 4] Figure 4 shows a grating spectrometer for simultaneously monitoring atomic emissions from many elements with fine spectral resolution.

[0015] [Figure 5] Figure 5 shows the parameters of the grating spectrometer.

[0016] [Figure 6A] FIG. 6A lists the spectral emissions around 240 nm for various elements that may be contained in earthen materials.

[0017] [Figure 6B] FIG. 6B lists the spectral emissions around 320 nm for various elements that may be contained in earthen materials.

[0018] [Figure 6C] FIG. 6C lists the spectral emissions around 346 nm for various elements that may be contained in earthen materials.

[0019] [Figure 6D] FIG. 6D lists the spectral emissions around 398 nm for various elements that may be contained in earthen materials. DETAILED DESCRIPTION OF THE INVENTION

[0020] 1. Millimeter-wave directed energy drilling system FIG. 1 shows a millimeter-wave (MMW) directed energy drilling system 100 having a plasma chamber 190 for analyzing exhaust from a borehole 110. The system 100 includes a high-power MMW source 120, such as a gyrotron, that generates high-power millimeter-wave radiation 103 in the 30-300 GHz frequency range at a power level of 0.1-2.0 MW. The high-power MMW radiation is coupled to a high-power transmission line 130 or waveguide that directs the high-power MMW radiation 103 to the bottom of the borehole 110. The high-power transmission line 130 or waveguide may include or be formed from a conductive material such as copper. A miter bend 132 may be used to fold the transmission line 130 and redirect the high-power MMW radiation 103 from a first direction to a second direction (e.g., from a horizontal direction to a vertical direction downward into the borehole 110). When the high power MMW borehole beam 105 is launched from the distal end of the transmission line 130, it melts and vaporizes the earth material at the bottom of the borehole 110, diffracting it so that the diameter of the borehole 110 is larger than the transmission line 130, creating an annular space for collection or discharge of the vaporized earth material in the exhaust stream 145.

[0021] The high-power transmission line 130 may be formed as a tube that also directs gas 135 to the bottom of the borehole 110. At near atmospheric pressure (e.g., 15-150 psi), the gas can be air, nitrogen, hydrogen, methane, or carbon dioxide. At higher pressures to a supercritical fluid state (e.g., >2,000 psi), the gas 135 can be a noble gas such as argon. The gas is injected into the high-power transmission line through a transmission line gas manifold 137. The injected gas 135 is transparent to the millimeter-wave radiation 130 and is at a pressure and velocity sufficient to prevent arcing. The gas ejects vapor and small particles (e.g., less than 10 μm in diameter) of vaporized earth material out of an annular space surrounding the distal end 138 of the high-power transmission line 130 as an exhaust stream 145.

[0022] The borehole 110 is capped by an exhaust line 112 and a feedthrough waveguide seal 114. The feedthrough waveguide seal 114 seals the borehole 110 and directs the exhaust flow 145 through the exhaust line 112. A sample tube 146, made of a metal or ceramic such as Inconel or alumina that may be present in high temperature exhaust environments (e.g., temperatures of at least 800°C or at least 1000°C), is inserted into the exhaust line 112 as it leads from the borehole 110 and redirects a portion of the exhaust flow 145 as a backflow into the plasma chamber 190. The sample tube 146 may be located near the borehole 110 or some distance away from the borehole to allow the gas to cool, if necessary. The sample tube 146 may connect to a sample port on the plasma chamber 190, allowing the gas to flow into the plasma chamber. The backflow rate into the plasma chamber 190 may be in the range of 5-25 ml / min. The exhaust wake may be less than 0.01%, 0.001%, or 0.0001% of the total exhaust flow, which may be greater than 1000 scfh (470 L / min). The exhaust wake may be, but need not be, a homogenous or uniform sample of the entire exhaust stream to identify potentially commercially valuable reserves.

[0023] As exhaust gases and particles from the wake enter the plasma chamber 190, they are ionized and heated by the MMW radiation, forming a plasma. A portion of the MMW radiation 103 can be collected (e.g., using an output coupler) and directed into the plasma chamber 190, decomposing, heating, and vaporizing the particles in the wake and exciting the resulting gases. In some cases, the collected radiation can excite gases injected into the plasma chamber through the gas purge inlet 127. The strong electric field from the focused MMW radiation 103 can ionize gas molecules and accelerate electrons, exciting the gases in the plasma chamber 190. The excitation of the gases into a plasma can produce optical radiation for spectroscopy, analysis, and determination of components in the exhaust stream 145.

[0024] A portion of the high-power MMW radiation 103 (e.g., about 1-3 kW) is directed to the plasma chamber 190 by the harvesting transmission line 131. In some implementations, a reflective power isolator 180 may be inserted along the high-power transmission line 130, as shown in FIG. 1, to harvest power that is reflected back from the molten target at the bottom of the borehole 110. A window seal 125 and a gas purge inlet 127 at or near the interface between the reflective power isolator 180 and the harvesting transmission line 131 prevent plasma propagation from the plasma chamber 190 to the high-power transmission line 130.

[0025] Spectrometer 185 analyzes the optical emissions from the plasma in plasma chamber 190 to provide an indication of the elemental composition of the vaporized earthen material from borehole 110. Fiber optic cable 195 transmits infrared (IR), visible, and / or ultraviolet (UV) light emitted by the plasma from plasma chamber 190 to spectrometer 185. The spectrometer measures 10 μg / m 3 The emission spectrum is resolved finely enough and with sufficient sensitivity to determine the elemental composition of the vaporized earth material with better sensitivity than

[0026] The plasma chamber 190 and spectrometer 185 may be calibrated by a calibration source 197 connected to the sample tube 146. The calibration source 197 injects a known concentration of an element of interest on command to provide a span signal for calibration of the element concentration in the exhaust stream 145 from the borehole 110. During calibration, the exhaust stream 145 may or may not be valved off from the plasma chamber by a control valve 148 in the sample tube 146. Alternatively, the control valve 148 may or may not be used to valve off gas from the calibration source. In some cases, the control valve 148 may not be included in the system. Elements of interest include, but are not limited to, commercially valuable metals such as copper, nickel, or lithium, and precious metals such as gold, platinum, or silver. Calibrations may be performed periodically or on demand in real time as the borehole 110 is deepened, for example, to account for the potentially changing composition of the exhaust stream 145 due to the chemistry of different rock formations penetrated by the high-power millimeter-wave borehole beam 105. Changes in the chemistry of the earthen material formations may affect the plasma efficiency of atomic emission excitation by altering the temperature and density of plasma electrons, which in turn may alter the electron atom excitation efficiency.

[0027] Optional monitoring equipment 170 coupled to the miter bend 132 may monitor the depth and / or rate of penetration of the borehole 110 using a small signal monitoring signal (not shown) that co-propagates with the high-power millimeter-wave radiation 103 along the high-power transmission line 130. The monitoring signal may be pulsed, chirp-like, or constant frequency, and may be at a different frequency than the high-power millimeter-wave radiation 103. The monitoring signal may reflect off the rock face or material at the bottom of the borehole 110. This reflection propagates down the high-power transmission line 130 to the monitoring equipment 170, which senses the interference of the reflection with a local oscillator. The interference may be used to derive the depth and / or rate of penetration of the borehole 110. Further details of the monitoring device may be found in U.S. Patent Application No. 63 / 291,731, filed December 20, 2021, entitled "Rate of Penetration / Depth Monitor for a Millimeter-Wave Beam made Hole," and its corresponding concurrently filed non-provisional international application (Attorney Docket No. MIT-23062WO01), entitled "Rate of Penetration / Depth Monitor for a Borehole formed with Millimeter-Wave Beam," both of which are incorporated herein by reference in their entireties.

[0028] 2. Plasma Chamber 2 shows the plasma chamber 190 in more detail. The plasma chamber 190 is an airtight, millimeter-wave power-leakage-tight enclosure into which the collection portion 104 and exhaust wake 202 of the high-power MMW radiation 103 are introduced. The millimeter-wave radiation 103 is launched into free space in the plasma chamber 190 toward a focusing mirror 210, which focuses the MMW radiation 103 into a diffraction-limited spot 220 approximately 2-4 wavelengths wide. This increases the electric field strength at the spot 220 to approximately 10 kV / cm or greater, generating and sustaining a plasma 205.

[0029] The sample tube 146 passes partway through the plasma chamber 190. Its output aperture 149 is located near the edge of the focused spot 220 that the MMW radiation 103 forms after reflecting off the focusing mirror 210. The exhaust gas wake 202 exits the sample tube 146 and enters the focused spot 220, and the focused MMW radiation 103 and plasma 205 (once present) can heat the exhaust wake 202. The heating can make particles, if present within the wake 202, more susceptible to decomposition. The heated exhaust can also act as a thermionic emitter to anchor the plasma 205 to the wake 202 at the focused spot 220. An initiating spark from a Tesla coil or antenna wire can be used to initiate decomposition from a cold start.

[0030] A fiber optic cable 195 is introduced through a small hole in the plasma chamber 190 to view the plasma 205 and transmit IR, visible, and / or UV light emissions to a spectrometer 185 for analysis.

[0031] The output exhaust 230 directs gas from the plasma chamber 190 to the final exhaust. The output exhaust 230 is maintained at a pressure slightly lower than the gas input from the sample tube 146 and the sampling line 131. The output exhaust 230 is also twisted to induce millimeter-wave mode conversion and is made of millimeter-wave opaque dielectrics and / or low electrical conductivity metals to efficiently absorb higher-order modes. The twisting and use of absorbing materials reduces or prevents millimeter-wave power from propagating from the plasma chamber 190 to the environment.

[0032] 3. Calibration source 3 shows an example of a calibration source 197 for more detailed quantitative monitoring of elemental concentrations in the borehole exhaust stream 145. The calibration source 197 may be configured to measure a known concentration of the element being monitored, e.g., 100 μg / m 3 is periodically introduced into the exhaust wake 202 to provide a span calibration that matches the unknown atomic emission level.

[0033] Calibration source 197 can generate aerosol 305 as follows: A calibrated standard solution 310 of the elements to be monitored, for example, with a concentration of 200 μg / ml of each element in a weak acid solution, is pumped by peristaltic pump 320 at a nominal rate of approximately 1 ml / min into nebulizer 330 (e.g., a Mienhard nebulizer). Nebulizer 330 is operated by a compressed gas flow (e.g., nitrogen at a flow rate of approximately 1 L / min) from cylinder 340 or other source and gas flow controller 350. Nebulizer 330 converts liquid standard solution 310 into an aerosol that is filtered into large droplets by atomization chamber 360. The filtered large droplet liquid is collected in waste container 370, which is attached to atomization chamber 360 by a sealed connection.

[0034] The concentration of the standard solution elements injected into the exhaust wake 202 should be accurately known for quantitative monitoring. The concentration C can be determined by the following formula:

number

[0035] 4.Spectrometer Atomic emission from neutral atoms, rather than ionized atoms, can dominate the emission spectrum from atmospheric pressure plasmas, with typical electron temperatures below 1 eV, because local thermodynamic equilibrium limits the number of energetic electrons that can ionize atoms. Table 1 lists some of the prominent neutral atomic emission wavelengths in air for metals and rare earth elements in the UV light wavelength range. A spectrometer 185 with fine resolution for these wavelengths can be used to distinguish species in the plasma. A spectral resolution of better than 0.05 nm across the emission spectral range is desirable. The spectrometer 185 can also have a wide spectral range to encompass as many elements as possible. [Table 1] JPEG0007824689000003.jpg192170 Table 1. Prominent UV atomic emission wavelengths for metals and rare earth elements

[0036] Figure 4 shows a spectrometer 185 for monitoring multi-element emissions in the exhaust wake 202 (Figure 2) with fine spectral resolution. Spectrometer 185 includes an entrance slit 405, a concave input mirror 410, a grating 420, several concave output mirrors 430, and several linear detector arrays 440. (Similar performance can be achieved with many compact spectrometers with narrow wavelength ranges.) While Figure 4 shows three concave output mirrors 430 and linear detector arrays 440, other spectrometers may have more or fewer concave output mirrors and linear detector arrays.

[0037] Fiber optic cable 195 directs the plasma emission to entrance slit 405, which may be approximately 10 nm wide and is the focal point of concave input mirror 410. Concave input mirror 410 images the light transmitted through slit 405 onto grating 420, which diffracts different spectral components at angles proportional to their wavelengths. Concave output mirror 430 distributes the diffraction pattern at different angles, focusing different portions of the diffracted light from the grating onto respective linear detector arrays 440. In FIG. 4 , there is one linear detector array 440 for each concave output mirror 430. Each detector array 440 monitors the wavelength range intercepted by the corresponding concave output mirror 430. In other implementations, one linear detector array or one two-dimensional detector array may be used to record the emissions reflected from all output mirrors 430. The detector arrays 440 are connected to a computer, processor, and / or other signal processing electronics (not shown) for signal analysis, data storage, and / or display.

[0038] The dimensions, angle, wavelength resolution, and detector array bandwidth of a grating spectrometer can be determined by the following three equations: Equation 2 is the standard grating diffraction angle equation, Equation 3 is the wavelength resolution equation, and Equation 4 is the detector array bandwidth equation. θ D =arcsin(λn-sinθ i ) (2)

number

[0039] 5 shows the parameters in Equations 2 to 4. These parameters are defined as follows: θ D - Diffraction angle from grating 420 θ i angle of incidence on grating 420 λ-wavelength n-lattice groove density L—distance from output mirror 430 to detector array 440 w—the width of one sensor pixel 442 in the detector array 440 Total length of Y-detector array 440

[0040] Table 2 shows the results of calculations using Equations 2-4 for a grating spectrometer 185 with a grating groove density of 2400 gr / mm and four 2048-pixel linear detector arrays 440 with 14 μm-wide pixels. The detector arrays 440 can monitor different bands with a spectral resolution of 0.016 nm or less. Each band is approximately 16 nm wide, and in this example, has wavelengths in the 200-800 nm range. This spectrometer can detect any of 35 elements in the exhaust wake, including the commercially valuable metals copper, aluminum, nickel, titanium, lithium, palladium, gold, and silver. Other spectrometers may have other numbers of bands (e.g., three, five, or six), bandwidths (e.g., 20 nm, 25 nm, 30 nm), and / or spectral resolutions (e.g., 0.1 nm, 0.2 nm, 0.3 nm, etc.), and may be able to detect different numbers and types of elements. [Table 2] Table 2. Diffraction angle, resolution and bandwidth with a 2048-pixel linear detector array with a 2400 gr / mm diffraction grating and 14 μm-wide pixels.

[0041] Figures 6A-6D list four bands of spectral emission for various elements that can be used to detect the presence of valuable elements. Figure 6A shows the emission in the 240 nm band, Figure 6B shows the emission in the 320 nm band, Figure 6C shows the emission in the 346 nm band, and Figure 6D shows the emission in the 398 nm band. For many elements, more than one wavelength can be detected, ensuring unambiguous identification of the element. Many rare earth elements are included along with silicon and carbon. Monitoring silicon concentration indicates the type of earth material being drilled. The presence of carbon indicates involvement of hydrocarbon compounds. Additional channels can be added to increase the number of elements monitored. Thus, a comprehensive and rapid investigation of the subsurface chemistry within a borehole 110 can be achieved during borehole drilling with this technique.

[0042]

[0010] Apparatus for continuously monitoring emissions from a borehole drilled by a millimeter wave directed energy borehole beam may be implemented and / or included within a borehole system in a variety of configurations. Exemplary configurations are listed below. Corresponding methods for monitoring emissions may also be implemented. (1) A method for monitoring emissions from a borehole drilled with a millimeter-wave directed energy borehole beam, the method comprising: receiving exhaust gases produced by vaporizing earthen material with the millimeter-wave directed energy borehole beam in a plasma chamber; heating the exhaust gases with electromagnetic radiation to produce a plasma and optical radiation from the plasma in the plasma chamber; performing spectroscopic measurements of the optical radiation with a spectrometer; and determining a composition of the exhaust gases based on the spectroscopic measurements of the optical radiation. (2) The method of (1), further comprising receiving, in a plasma chamber, a portion of the millimeter-wave radiation used to create the millimeter-wave directed energy borehole beam, and focusing the portion of the millimeter-wave radiation to provide the electromagnetic radiation that generates the plasma. (3) The method of (2), further comprising collecting a portion of the millimeter wave radiation returned from reflection of the millimeter wave borehole beam from the bottom of the borehole. (4) The method according to any one of (1) to (3), further comprising calibrating the spectrometer. (5) The method of (4), wherein calibrating the spectrometer includes introducing an aerosol into the plasma chamber from a calibration source, the aerosol supplying a known amount of an element from the calibration source to the plasma; measuring a level of optical emission from the plasma while the aerosol is present in the plasma, the level of optical emission indicating the amount of the element; and determining the amount of the element in the exhaust gas from the level of optical emission. (6) A method according to any one of (1) to (5), wherein receiving the exhaust gas produced by vaporizing the earthen material includes receiving the particles by a gas flow from a borehole into a sample tube connected to the plasma chamber. (7) A system for monitoring the composition of earth material in a borehole produced by a millimeter-wave directed energy downhole beam, the system comprising: a plasma chamber for receiving exhaust gases from the borehole and for receiving a portion of the millimeter-wave radiation used to create the millimeter-wave downhole beam, the plasma chamber configured to heat the exhaust gases with the portion of the millimeter-wave radiation to produce plasma-emitted optical radiation; and a spectrometer in electromagnetic communication with the plasma chamber for measuring a spectrum of the optical radiation from the plasma, the spectrum indicative of the composition of the earth material in the borehole. (8) The system of (7), further comprising a sample tube or sample port connected to the plasma chamber for receiving exhaust gases from the borehole, and an exhaust tube or exhaust port connected to the plasma chamber for exhausting at least the exhaust gases from the plasma chamber. (9) The system of (8), wherein the sample tube or sample port is made of a material that can withstand temperatures of at least 800°C. (10) A system according to any one of the configurations (7) to (9), wherein the spectrometer is a grating spectrometer configured to monitor at least one band having a bandwidth of 20 nm and a center wavelength in the range of 200 nm to 800 nm with a spectral resolution of 0.02 nm or better. (11) The system of any one of (7) to (10), further comprising a mirror disposed within the plasma chamber for focusing a portion of the millimeter-wave radiation onto a spot, and a sample tube extending into the plasma chamber for venting exhaust gases from the borehole into the plasma chamber adjacent the spot. (12) The system of (11), further comprising a fiber optic cable connected to the plasma chamber and arranged to receive optical radiation from the spot and direct the optical radiation to the spectrometer. (13) The system of any one of (7) to (12), further comprising a calibration source in fluid communication with the plasma chamber for providing an aerosol to the plasma chamber for calibration of the spectrometer. (14) The system of any one of (7) to (13), further comprising a reflective power isolator in electromagnetic communication with the plasma chamber for coupling a portion of the millimeter-wave radiation external to the transmission line that directs the millimeter-wave radiation to the bottom of the borehole to form a millimeter-wave directed energy downhole beam. (15) A system for drilling a borehole and monitoring emissions from the borehole, the system comprising: a high power millimeter wave (MMW) source; a waveguide for carrying MMW radiation from the MMW source to the borehole; exhaust piping for sealing the borehole and capturing exhaust gases from the borehole while the borehole is being deepened with an MMW drilling beam formed from the MMW radiation; a plasma chamber in fluid communication with the exhaust piping for receiving an exhaust wake sampled from the exhaust gases; and a spectrometer in electromagnetic communication with the plasma chamber for detecting emissions from a plasma formed in the plasma chamber from the exhaust wake. (16) The system of configuration (15), further comprising a reflective power isolator in electromagnetic communication with the plasma chamber for coupling a portion of the MMW radiation generated by the MMW source to the plasma chamber. (17) The system of configuration (16), further comprising: a mirror disposed within the plasma chamber for focusing a portion of the MMW radiation to a spot within the plasma chamber; and a sample tube extending into the plasma chamber for ejecting an exhaust wake into the plasma chamber near the spot. (18) The system of (17), further comprising a fiber optic cable connected to the plasma chamber and arranged to receive the optical radiation from the spot and direct the optical radiation to the spectrometer. (19) A system according to any one of the configurations (15) to (18), wherein the spectrometer is a grating spectrometer configured to monitor at least one band having a bandwidth of 20 nm and a center wavelength in the range of 200 nm to 800 nm with a spectral resolution of 0.02 nm or better. (20) The system of any one of configurations (15) to (19), further comprising a calibration source in fluid communication with the plasma chamber for providing an aerosol to the plasma chamber for calibration of the spectrometer.

[0043] 6. Conclusion All parameters, dimensions, materials, and configurations described herein are meant to be exemplary, and actual parameters, dimensions, materials, and / or configurations will depend on the particular application in which the teachings of the present invention are used. Accordingly, it is to be understood that the foregoing embodiments are presented primarily by way of example, and that, within the scope of the appended claims and their equivalents, embodiments of the present invention may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and / or methods is within the scope of the present disclosure, provided that such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent.

[0044] Also, various inventive concepts may be embodied as one or more methods, of which at least one example is provided. Acts performed as part of a method may, in some cases, be ordered differently. Thus, in some inventive implementations, the respective acts of a given method may be performed in a different order than specifically illustrated, which may include performing some acts simultaneously (even though such acts are shown as sequential acts in an illustrative embodiment).

[0045] All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.

[0046] All definitions defined and used herein should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0047] The indefinite articles "a" and "an," as used in the specification and claims, unless expressly indicated to the contrary, should be understood to mean "at least one."

[0048] The term "and / or," as used in the specification and claims, should be understood to mean "either or both" of the elements so conjoined, i.e., elements present conjunctively in some cases and disjunctively in other cases. Multiple elements listed with "and / or" should be construed in the same manner, i.e., "one or more" of the elements so conjoined. Other elements, whether related or unrelated to the elements specifically identified, may optionally be present other than the elements specifically identified by the "and / or" clause. Thus, as a non-limiting example, a reference to "A and / or B," when used in combination with open-ended language such as "comprising," may refer in one embodiment to A only (optionally including elements other than B); in another embodiment to B only (optionally including elements other than A); in yet another embodiment to both A and B (optionally including other elements), etc.

[0049] As used herein and in the claims, "or" should be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" shall be interpreted as being inclusive, i.e., including at least one of, but also including two or more of, the several or listed elements and, optionally, additional unlisted items. Terms expressly indicated to the contrary, such as "only one of" or "only one of," or, when used in the claims, "consisting of," only refer to the inclusion of exactly one element of the several or listed elements. In general, the term "or" as used herein shall only be interpreted as indicating exclusive alternatives (i.e., "one or the other, but not both") when preceded by terms of exclusivity, such as "either," "one of," "only one of," or "only one of." As used in the claims, "consisting essentially of" shall have its ordinary meaning as used in the field of patent law.

[0050] As used in this specification and claims, the term "at least one" in connection with a list of one or more elements should be understood to mean at least one element selected from one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This definition also allows for the optional presence of elements other than those specifically identified in the list of elements to which the phrase "at least one" refers, whether related or unrelated to the specifically identified elements. Thus, as a non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B," or, equivalently, "at least one of A and / or B") can refer in one embodiment to at least one, optionally two or more, A, and no B (and optionally including elements other than B); in another embodiment to at least one, optionally two or more, B, and no A (and optionally including elements other than A); in yet another embodiment to at least one, optionally two or more, A, and at least one, optionally two or more, B (and optionally including other elements); and so forth.

[0051] In the claims and the above specification, all transitional phrases, such as "comprising," "including," "holding," "having," "including," "involving," "holding," "consisting of," etc., are to be understood to be open-ended, i.e., meaning including, but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively, as defined in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

1. 1. A method for monitoring emissions from a borehole drilled with a millimeter wave directed energy borehole beam, comprising: receiving exhaust gases produced by vaporizing earth material with said millimeter wave directed energy borehole beam within a plasma chamber; heating the exhaust gas with electromagnetic radiation to generate a plasma and optical radiation from the plasma in the plasma chamber; performing a spectroscopic measurement of said optical radiation with a spectrometer; and determining a composition of the exhaust gas based on the spectroscopic measurement of the optical radiation.

2. receiving, in the plasma chamber, a portion of millimeter-wave radiation used to create the millimeter-wave directed energy borehole beam; and The method of claim 1 , further comprising focusing a portion of the millimeter-wave radiation to provide the electromagnetic radiation that generates the plasma.

3. 3. The method of claim 2, further comprising collecting the portion of the millimeter-wave radiation returned from a reflection of the millimeter-wave directed energy borehole beam from the bottom of the borehole.

4. The method of claim 1 , further comprising calibrating the spectrometer.

5. Calibrating the spectrometer comprises: introducing an aerosol into the plasma chamber from a calibration source, the aerosol providing a known amount of an element from the calibration source to the plasma; measuring a level of optical emission from the plasma while the aerosol is present in the plasma, the level of optical emission being indicative of the amount of the element; and 5. The method of claim 4, further comprising determining the amount of said element in said exhaust gas from said optical emission level.

6. 10. The method of claim 1, wherein receiving the exhaust gas produced by vaporizing earthen material comprises receiving particles by a gas flow from the borehole into a sample tube connected to the plasma chamber.

7. 1. A system for monitoring the composition of earth material in a borehole generated by a millimeter wave directed energy downhole beam, comprising: a plasma chamber for receiving exhaust gases from the borehole and for receiving a portion of millimeter-wave radiation used to create the millimeter-wave directed energy borehole beam, the plasma chamber configured to heat the exhaust gases with the portion of millimeter-wave radiation to produce plasma-emitted light radiation; and a spectrometer in electromagnetic communication with the plasma chamber for measuring a spectrum of the optical emission from the plasma, the spectrum indicative of the composition of the earthen material in the borehole.

8. a sample tube or sample port connected to the plasma chamber for receiving the exhaust gas from the borehole; The system of claim 7 , further comprising an exhaust pipe or port connected to the plasma chamber for exhausting at least the exhaust gases from the plasma chamber.

9. The system of claim 8 , wherein the sample tube or sample port is made of a material that can withstand temperatures of at least 800° C.

10. 8. The system of claim 7, wherein the spectrometer is a grating spectrometer configured to monitor at least one band having a bandwidth of 20 nm and a center wavelength in the range of 200 nm to 800 nm with a spectral resolution of 0.02 nm or better.

11. a mirror disposed within the plasma chamber for focusing the portion of the millimeter-wave radiation into a spot; 8. The system of claim 7, further comprising a sample tube extending into the plasma chamber for ejecting the exhaust gas from the borehole into the plasma chamber adjacent the spot.

12. The system of claim 11 , further comprising a fiber optic cable connected to the plasma chamber and disposed to receive the optical radiation from the spot and direct the optical radiation to the spectrometer.

13. The system of claim 7 , further comprising a calibration source in fluid communication with the plasma chamber for providing an aerosol to the plasma chamber for calibration of the spectrometer.

14. 8. The system of claim 7, further comprising a reflective power isolator in electromagnetic communication with said plasma chamber for coupling said portion of said millimeter-wave radiation out of a transmission line that directs said millimeter-wave radiation to the bottom of said borehole to form said millimeter-wave directed energy downhole beam.

15. 1. A system for drilling a borehole and monitoring discharges from said borehole, comprising: a high-power millimeter wave (MMW) source; a waveguide that carries MMW radiation from said MMW source to said borehole; an exhaust line for sealing the borehole and capturing exhaust gases from the borehole while the borehole is being deepened with a MMW drilling beam formed from the MMW radiation; a plasma chamber in fluid communication with the exhaust line for receiving exhaust wake sampled from the exhaust gas; a spectrometer in electromagnetic communication with the plasma chamber for detecting emissions from the plasma formed in the plasma chamber from the exhaust wake; the system comprising a reflective power isolator in electromagnetic communication with the plasma chamber for coupling a portion of the MMW radiation generated by the MMW source to the plasma chamber.

16. a mirror disposed within the plasma chamber for focusing the portion of the MMW radiation to a spot within the plasma chamber; 16. The system of claim 15, further comprising a sample tube extending into the plasma chamber for discharging the exhaust wake into the plasma chamber near the spot.

17. 17. The system of claim 16, further comprising a fiber optic cable connected to the plasma chamber and arranged to receive optical radiation from the spot and direct the optical radiation to the spectrometer.

18. 16. The system of claim 15, wherein the spectrometer is a grating spectrometer configured to monitor at least one band having a bandwidth of 20 nm and a center wavelength in the range of 200 nm to 800 nm with a spectral resolution of 0.02 nm or better.

19. 16. The system of claim 15, further comprising a calibration source in fluid communication with the plasma chamber for providing an aerosol to the plasma chamber for calibration of the spectrometer.

20. A system for drilling a borehole and monitoring discharges from said borehole, comprising: a high-power millimeter wave (MMW) source; a waveguide that carries MMW radiation from said MMW source to said borehole; an exhaust line for sealing the borehole and capturing exhaust gases from the borehole while the borehole is being deepened with a MMW drilling beam formed from the MMW radiation; a plasma chamber in fluid communication with the exhaust line for receiving exhaust wake sampled from the exhaust gas; a spectrometer in electromagnetic communication with the plasma chamber for detecting emissions from the plasma formed in the plasma chamber from the exhaust wake; the system comprising a calibration source in fluid communication with the plasma chamber for providing an aerosol to the plasma chamber for calibration of the spectrometer.

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