Beam monitor and method of use thereof

Abstract

Beam monitors, methods of use, and methods of manufacture are provided herein. The beam monitor may include a rounded beam cavity having one or more waveguides attached thereto, signals from the one or more waveguides may be used to determine one or more beam characteristics. Such a monitor may include a beam intensity monitor that includes a cylindrical beam cavity having a rectangular waveguide extending from a periphery from which a beam intensity may be determined. The advanced beam monitor may include a multi-mode beam cavity having a plurality of waveguides connected at different locations, each location corresponding to a different excitation mode. Such a monitor may include an elliptical beam cavity and five waveguides connected thereto, signals from the five waveguides may be used to determine beam charge, beam position, and beam size in x-and y-directions. The beam monitor may be a separate device and may also be integrated within the linear accelerator. The accelerator may include an off-axis beam monitor coupling port and an on-axis tuning feature.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This PCT application claims the benefit of priority to U.S. Provisional Application No. 63 / 392,015, filed on July 25, 2022, the entire contents of which are incorporated herein by reference. STATEMENT AS TO RIGHTS TO INVENTS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

[0002] This invention was made with government support under Grant DE-SC0019574 awarded by the U.S. Department of Energy. The government has certain rights in this invention. Background Art

[0003] The present invention relates generally to beam monitors, and more particularly to beam monitors for measuring beam characteristics in medical linear accelerators.

[0004] Existing large linear accelerator systems in national laboratories as well as industrial and medical accelerators require accurate and real-time beam control systems, especially for accelerators used in radiotherapy. For safety purposes, full beam information needs to be monitored to tune or shut down the beam on a fast time scale, however, existing beam monitors can usually only measure certain properties at a time. For example, the measurement of one property may adversely affect the measurement of another property. Therefore, for some settings, the measurement of full beam information may not be feasible, or may require complex processes, indirect measurements, or multiple separate measurement devices, which further increases the size and complicates manufacturing.

[0005] Therefore, there is a need for an improved beam monitor device that allows accurate measurement of beam information in a simple, non-destructive manner. There is also a need for a device that provides complete beam information and is relatively compact and can be incorporated into a single device and integrated into an overall system. Summary of the invention

[0006] The present invention relates generally to beam monitors, and more particularly to beam monitors for measuring beam characteristics in medical linear accelerators.

[0007] In one aspect, the present invention relates to a beam intensity monitor comprising a rounded or circular beam cavity having a central input and output, and coupled to a waveguide through which the intensity of the beam can be measured. In some embodiments, the output is substantially larger in diameter than the input (e.g., four times or more of the input). In some embodiments, the beam monitor comprises a single circular beam cavity and a rectangular waveguide coupled to the beam cavity through a ceramic window. In some embodiments, the waveguide extends from the periphery of the beam cavity. The beam monitor can be integrally formed with the accelerator body of the linear accelerator, with the beam cavity located at the distal end, or the beam monitor can be manufactured separately as a stand-alone device and coupled to an existing accelerator. The beam monitor can be further incorporated into a control system that determines the beam intensity based on the signal from the waveguide, thereby measuring the beam intensity directly from the beam in real time, which can be fed back into the beam control system.

[0008] In another aspect, the present invention relates to an advanced beam monitor that simultaneously measures multiple beam characteristics from a beam by utilizing multiple waveguides coupled at different locations on a multimode beam cavity, each location corresponding to a different mode. In some embodiments, the beam cavity is elliptical with an eccentricity sufficient to shift the frequency of an excitation mode into two modes, thereby allowing sufficient excitation modes to measure additional beam characteristics, such as beam position and size in the x-direction and the y-direction. In some embodiments, the beam monitor is configured to detect beam charge, beam position (both x and y), and beam size (both x and y). In some embodiments, the beam monitor includes five excitation modes and five waveguides connected to the beam cavity through RF windows at different locations to allow detection of signals from each of the corresponding excitation modes. In some embodiments, the beam unit includes one waveguide coupled to the periphery of the elliptical beam cavity, two waveguides coupled to one major face of the beam cavity, and two waveguides coupled to the opposite major face of the beam cavity, thereby allowing simultaneous measurement of signals from each of the five modes in a relatively compact device. A beam monitor may further be incorporated into the control system for measuring beam characteristics in real time directly from the beam via a signal from the waveguide, which may be fed back into the beam control system.

[0009] In another aspect, the present invention relates to a method for manufacturing a linear accelerator with an integrated beam monitor, wherein one or more coupling ports for the beam monitor are off-axis from the linear accelerator so that tuning of the cavity can be performed from an on-axis tuning pin or feature. In some embodiments, the integrated beam monitor includes two ports, which allows the quality factor ("Q factor") of the beam monitor to be reduced to any desired value and thus control the amount of radiation received from one of the coupling ports. This control results in saving external components required to attenuate the strong signal emitted from the beam monitor. On the other hand, if the current passed is too small to generate an RF signal, the Q factor can be increased. By measuring the phase of the signal from the beam monitor and combining it with the linear accelerator simulation, the energy of the beam can be estimated. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1A-Figure 1C The figures illustrate side, end, and top views of a beam intensity monitor according to some embodiments.

[0011] Figure 1D The diagram shows Figure 1A Electric field diagram of the beam monitor in .

[0012] Figure 2 A diagram illustrates a linear accelerator model with an integrated beam intensity monitor in accordance with some embodiments.

[0013] Figure 3 A prototype of an exemplary beam monitor and associated cold test results are shown in accordance with some embodiments.

[0014] Figure 4 The figure shows the electric field diagram for five different modes of the central cavity of the beam cavity of an advanced beam monitor according to some embodiments.

[0015] Figure 5A-5E The graph shows electric field plots for five different modes of a beam monitor with a given coupler (exemplary beam monitor) according to some embodiments.

[0016] Figure 6A-6D The figures illustrate various views of an advanced beam monitor according to some embodiments.

[0017] Figure 7 The figure illustrates another view of an advanced beam monitor showing the RF windows and ports associated with each waveguide in accordance with some embodiments.

[0018] Figure 8 Shown is a readout circuit for simultaneously measuring signals from each of five waveguide ports in accordance with some embodiments.

[0019] Fig. 9A method of monitoring beam intensity using a beam monitor according to some embodiments is shown.

[0020] Fig.10 A method of monitoring beam integrity beam information using an advanced beam monitor according to some embodiments is shown.

[0021] Fig.11 A portion of a linear accelerator with an integrated beam monitor is shown in accordance with some embodiments.

[0022] Fig.12 Shown is a cross-sectional view of a portion of a linear accelerator with an integrated beam monitor in accordance with some embodiments. DETAILED DESCRIPTION

[0023] The present invention relates to a beam monitor for a linear accelerator (LINAC).

[0024] Existing conventional linear accelerator systems in national laboratories, as well as industrial and medical accelerators, require accurate and real-time beam control systems, especially for accelerators used in radiation therapy, which requires more complete information about beam characteristics. For safety purposes, it is necessary to monitor complete beam information in order to tune or shut down the beam on a fast time scale. Typically, the complete beam information includes at least beam intensity, position, and size information. In some embodiments, the beam information may include any of the following: operating mode, beam current, charge, position, size, emissivity, or any combination thereof. Existing beam monitors typically use beam current or bunching charge to measure the longitudinal mode of the beam. Beam position monitors measure beam position using transverse modes. The lower coupling between degenerate transverse modes reduces accuracy and sensitivity. Quadrupole modes can be used to measure beam size; but again, degeneration destroys accurate measurements.

[0025] Further information on conventional methods of measuring beam information and developments in this area may be obtained by reference to the following publications: R.H. Miller, J.E. Clendenin, M.B. James, and J.C. Sheppard, Proceedings of the 12th International Conference on High Energy Accelerators, Batavia, IL, USA, 1983; SLAC-PUB-3186; J.S. Kim, C.D. Nantista, R.H. Miller, and A.W. Weidemann, “A resonant cavity method for non-invasive pulse-to-pulse emission rate measurements,” Review of Scientific Instruments, vol. 76, pp. 109–125, 2005, 10.1063 / 1.2149191; Kim, Y.I., R. Ainsworth, A. Aryshev, S.T. Boogert, G. Boorman, J. Frisch, A. Heo, et al., “A Cavity Beam Position Monitor System at the Accelerator Test Facility 2,” Physical Review Special Topics: Accelerators and Beams, 15, no. 4 (2012): 042801; Jia-Hang, Sudu. Ying-Chao, Hua. Jian-Fei, Zheng Shu-Xin, Qiu Jia-Qi, Yang Jin, Huang Wen-Hui, CHEN Huai-Bi, and Tang Chuan-Xiang, “Design and Cold Test of a Rectangular Cavity Beam Position Monitor,” Chinese Journal of Physics, C 37, No. 1 (2013): 017002; Inoue, Yoichi, Hitoshi Hayano, Yosuke Honda, Toshikazu Takatomi, Toshiaki Tauchi, Junji Urakawa, Sachio Komamiya, et al., “Development of a High-Resolution Cavity Beam Position Monitor,” Physical Review Special Topics: Accelerators and Beams 11, No. 6 (2008): 062801; Walston, Sean, Stewart Boogert, Carl Chung, Pete Fitsos, Joe Frisch, Jeff Gronberg, Hitoshi Hayano et al., "Performance of a High-Resolution Cavity Beam Position Monitor System," Nuclear Instruments and Methods in Physics Research Part A: Accelerators, Spectrometers, Detectors, and Related Equipment 578, no. 1 (2007): 1-22, the entire contents of which are incorporated herein for all purposes.

[0026] In one aspect, a beam monitor as described herein can combine all modes of operation, longitudinal mode, transverse mode, and quadrupole mode, into one unit and effectively eliminate degradation. Such a beam monitor device can also be integrated within a LINAC, for example, by using separate structure manufacturing techniques. The method can be used to measure beam characteristics including the emissivity of the beam.

[0027] Currently, there is a large gap between deployed accelerator systems and treatment demand. As more reliable and cheaper accelerator systems become available, the number of such systems deployed will increase. The improved beam monitor described herein can become a key part of an accelerator system because it improves reliability and can reduce the overall cost of deploying such an accelerator system.

[0028] Although beam control is critical to the optimal operation of accelerators, both for large systems found in national and international laboratories and for industrial and medical accelerators, it is often compromised by the high cost of diagnostic detectors and the need for information from multiple detectors to generate a complete picture of what is happening to the beam. In addition, some measurements are destructive to the beam, rely on indirect beam measurements, or require lengthy and complex procedures to interpret the results. Ideally, a fast, non-destructive beam monitor would be preferred that could provide beam intensity, position, and size information almost instantaneously and could operate quickly enough to diagnose individual beam bunching. However, there is also a need for such a device to be cheap and economical enough for widespread use.

[0029] In some embodiments, the present invention relates to a cavity monitor that can directly and accurately measure beam intensity. In some embodiments, the present invention relates to a cavity monitor in which the azimuthal symmetry is perturbed and therefore the different polarizations of the dipole and quadrupole modes are offset in frequency. Adding this additional frequency information to the amplitude will allow a single cavity to provide at least five pieces of information related to the charge, horizontal and vertical dipole modes, and two polarizations of the quadrupole mode. This novel approach can provide a compact device that can non-destructively monitor beam position, size, and final emittance at high repetition rates. In addition, installing multiple monitors in the FODO lattice of a high energy accelerator (such as LCLS-II) allows for rapid emittance measurements. Three different beam monitors are described in the examples below, but it should be understood that these are merely examples and that variations of these embodiments can be implemented according to the inventive concepts described herein.

[0030] In a first aspect, the present invention relates to a beam intensity monitor that can be used in medical and industrial applications. The beam intensity monitor is a cavity monitor that can be manufactured separately and attached to an accelerator, or can be integrated with the accelerator itself. In some embodiments, the beam monitor includes a single rounded cavity (e.g., a cylindrical cavity), a ceramic window (e.g., an RF window), and a coupled waveguide (e.g., a rectangular waveguide). In this embodiment, the waveguide extends from the periphery of the circular beam cavity, the position corresponding to the excitation mode of the beam cavity, so that the measured energy within the rectangular waveguide corresponds to the beam intensity. The rectangular waveguide can be connected to a signal sensor, which in turn is connected to a control unit that processes the signal to determine the beam intensity and can optionally feed it back to the beam control to generate the desired beam intensity. In some embodiments, the ratio of the radius to the height of the cavity is maintained at 4:1 to allow the cavity to be constructed from two pieces cut along a plane passing through the centerline of the cavity. The electromagnetic simulations for the beam monitor cavity discussed herein have been performed using high frequency simulation software (HFSS).

[0031] Figure 1A-Figure 1C An example beam intensity monitor 100 is shown, and Figure 1D An electric field diagram of an exemplary beam monitor is shown. Figure 1A shows a side view in the x direction, Figure 1B shows an end view in the y direction, and Figure 1C A top view in the x-direction is shown. In this embodiment, the beam monitor 100 includes a circular beam cavity 10 extending along the xy plane and having an entrance tube 11 and an exit tube 12 extending in opposite directions from the center of the cavity along the z-axis. The beam cavity 10 is coupled to the waveguide w via a protrusion 13 that extends to a window 14 filled with a ceramic plug 15. As shown, the waveguide w extends from the periphery of the beam cavity 10. In this embodiment, the outlet 12 is substantially larger than the input 11 (e.g., four times larger or more), and the ratio of the radius to the height of the cavity is relatively small (e.g., 4:1 or less), so that the amount of beam energy transmitted to the waveguide w is relatively small (e.g., 300kW or less for a 3MW beam, typically 100kW or less for a 3MW beam). It should be understood that the design can be manufactured separately, or can be machined within the same metal block as the accelerator (e.g., Figure 2 In some embodiments, the readout circuitry can be used to diagnose bunching on a case-by-case basis.

[0032] The output power of the beam monitor is given by the following equation: in is the coupling coefficient, I is the current, R is the shunt impedance, Pout is the output of the beam monitor, Cavity Q o is 4019, and The shunt impedance is 3.17×10 5 . The results of the modal analysis of the cavity are listed in Table 1.

[0033] Table 1: Modal analysis of the 9.3 GHz cavity Mode Type frequency <![CDATA[Q0]]> <![CDATA[Q t ]]> (R / Q) <![CDATA[TM 010 ]]> 9.30GHz 4019 648 78.87Ω

[0034] Figure 2 A LINAC is shown with an integrated beam intensity monitor 100 shown in a cross-sectional view along a beamline. The LINAC comprises an electron gun 1 which injects electrons into a LINAC body 2 formed of a conductive material (e.g. copper) and in which is defined a series of multiple buncher cavities 3 and a beam cavity 10 for the beam monitor 100 at its distal end. It can be seen that the height of the beam cavity 10 is significantly smaller than the buncher cavity. The beam cavity 10 is intentionally designed to be less efficient than the buncher cavity so as to limit the energy generated in the cavity and transmitted to the waveguide, for example, 100kW or less will be transmitted for a 3MW beam. Accordingly, most of the beam energy is transmitted to the exit tube 12 and continues along the beamline. Along the top periphery of the beam cavity 10 is an opening filled with a ceramic plug (i.e., an RF window) which leads to a recess 16 (e.g., a RF window) which interfaces with the rectangular waveguide w. Figure 3 ). In this embodiment, the LINAC generates a 9.3 GHz beam and the accelerator body 2 has a width (w) of 5.17 cm and an overall length (l) of 58.77 cm. However, it will be appreciated that these concepts can be scaled accordingly to accommodate different sizes and frequencies of LINACs.

[0035] In some embodiments, the accelerator body and integrated beam monitor can be fabricated from a conductive metal such as copper, for example, with a separate design of upper and lower halves that assemble to form a beamline cavity, such as Figure 3 . As shown in the lower left, the top of the bottom plate is visible, showing the cavity 10 and two different sizes of inlet and outlet tubes 11, 12. At the top, the upper side of the upper plate is shown, illustrating the pill-shaped holes 14 holding the ceramic (e.g., alumina) plugs 15 and the pockets or recesses 16 holding the coupled waveguides w. Figure 3 The graph in shows the cold test results, which shows a resonant frequency of 9.338 GHz.

[0036] In a second aspect, the beam intensity monitor of FIG1 is manufactured separately and then attached at its distal end to an existing LINAC beamline. This embodiment is designed for applications where a standalone beam monitor is required, such as an aftermarket beam monitor that can be added to an existing medical or industrial LINAC. The beam monitor structure can be substantially similar in design to the integrated beam monitor described above. The beam unit can be designed for a specific LINAC frequency (e.g., 9.3 GHz), or can include a replaceable or tunable waveguide, allowing the beam monitor to be easily switched to other frequencies of the LINAC as required.

[0037] In a third aspect, the present invention relates to an advanced beam monitor that monitors multiple beam characteristics by using a multimode beam cavity and multiple waveguides attached thereto, each waveguide corresponding to a different mode in which the corresponding beam characteristic can be measured. Advantageously, the beam monitor design allows the beam characteristics to be measured directly from the beam in a non-destructive manner. This allows the complete beam information of the beam to be determined simultaneously and in real time, which can be fed back into the beam control, for example to adjust the position or size, or to adjust the treatment based on the beam intensity. The beam monitor is the most complex version of the beam monitor concept described herein. In this embodiment, the beam monitor is designed to monitor beam charge, position, size using only one cavity with multiple couplers to multiple waveguides. In Figure 5A An example of such a beam monitor is shown in , which shows a beam cavity 20 having an inlet and outlet as previously described, and a plurality of waveguides w coupled to and in communication with the beam cavity.

[0038] The geometry of the beam cavity 20 is chosen to be asymmetric to separate the modal frequencies of the different polarizations so that the position and size of the x-beam and y-beam can be distinguished using not only the coupling position but also the frequency discrimination. Figure 4 The beam cavity shown on the left in the center is not circular, but rather slightly elliptical, with the x dimension being larger than the y dimension (e.g., 5% larger or less, typically about 1-2%), at least enough to shift the frequencies of the excitation modes associated with each dimension, thereby creating a different excitation mode for each of the x and y dimensions. This decentering shifts the frequencies relative to at least two modes so that these modes can be used to determine position and size relative to the x and y axes.

[0039] Figure 4 Different excitation modes provided by the off-center beam cavity 20 are shown, including: TM 010 ,TM 110 ,TM 210 and the TM frequency shifted due to the eccentricity of the beam cavity 110 ,TM 210 The following table 2 lists Figure 4 Characteristic parameters of the electric field shown in .

[0040] Table 2: Modal analysis of the 5.712 GHz cavity

[0041] Figure 5A The beam monitor 200 shown in FIG. 1 further includes five waveguide couplers along the beam cavity, which are designed for the five excitation modes. RF windows (e.g., ceramic-filled openings) for vacuum isolation are located at the output port of the beam cavity connected to waveguide couplers, which are connected to the five waveguides (see also FIG. 1 ). Figure 7 ). Figure 4 A- Figure 4 B shows five different excitation modes simultaneously present in the off-center cavity 20, and indicates (by arrows) the specific rectangular waveguide w that is optimally positioned to detect signals from each of the corresponding excitation modes. Due to the limited clearance around the beam cavity, the rectangular waveguide has been precisely placed in a specific position that allows accurate signal detection from each of the five excitation modes simultaneously.

[0042] In this embodiment, at the periphery of the beam cavity (see Figure 4 A) A rectangular waveguide for detecting the beam charge is positioned at different locations along the top major surface (see Figure 4 B and Figure 4 C) Two rectangular waveguides are positioned for detecting the beam position along each of the x-axis and the y-axis, at different locations along the bottom major face (see Figure 4 C and Figure 4 D) Two rectangular waveguides are positioned for detecting beam size along each of the x-axis and y-axis. This particular arrangement is advantageous because it allows all of the above beam characteristics to be determined (ie, complete beam information), but still allows the beam monitor to be relatively compact, even integrated within a LINAC.

[0043] On the other hand, a multi-channel readout circuit can be used to process the signal from each waveguide simultaneously so that the beam characteristics can be determined simultaneously and in real time. In the embodiment shown, the cavity is designed at 5.712 GHz, which is half the operating frequency of medical LINACs used for various high-energy radiation therapy applications. The output model frequency covers 5.712 GHz. It should be understood that these same design concepts can be scaled and / or alternated for other frequencies. Additionally, while five waveguides are shown here, it should be understood that various other embodiments may include more or fewer waveguides, depending on the application and beam characteristics to be determined.

[0044] To maintain the ultra-high vacuum inside the cavity, an RF window for vacuum isolation is located at the output port of the cavity connected to the waveguide. Alumina substrates with 99.5% or higher purity are selected for fabrication. In some embodiments, the alumina substrate is brazed to the cavity and then the waveguides are brazed together. Figure 5A The geometric shapes of the five couplers and their field patterns in five different modes are shown in FIG.

[0045] TM 010 ,TM 110 and TM 210 The output voltage of the mode is given by: Where ω is the angular frequency, and q is the charge / bunching, Q is R s is the shunt impedance, is the coupling coefficient, ρ is the kick factor, The positions of the charge in the x and y directions are dx and dy, and The changes in position are δx and δy, and the bunching sizes are δx and δy. Unipolar Mode (TM 010 ) output signal power is proportional to the square of the beam charge. 110 ) is sensitive to the beam position in the x or y direction. 210 ) is determined by the beam position and beam size in the x and y directions.

[0046] Figure 6A-6D Various views of a mechanical representation of an advanced beam monitor (e.g., a 5.712 GHz beam monitor) are shown. In some embodiments, a direct conversion architecture is utilized in the readout circuit. Commercial RF receivers can be used and typically cover up to 6 GHz. Downconverter devices can be used to mix the high order mode output power to less than 6 GHz. Figure 8 A schematic diagram of an exemplary readout circuit for a 5.712 GHz design is shown in In this readout circuit, a total of nine channels are recorded from five ports.

[0047] Figure 7 Another view of the advanced beam monitor 200 is depicted which more clearly shows the RF windows 14, 15 between the respective waveguides and the beam cavity, and which further shows ports 1-5 associated with waveguides w1-w5, ports 1-5 including signal detectors for measuring the signal from each waveguide, the signal detectors being used to Figure 8It should be understood that this is just one implementation and that variations of advanced beam monitors and associated readout circuits may be implemented in accordance with the inventive concepts described herein.

[0048] Figure 9-10 An example method of using the beam monitor described above is depicted. Fig. 9 A method for determining beam intensity using the above-mentioned beam intensity monitor is provided. The method may include the following steps: transmitting an accelerated energy beam generated by a linear accelerator into a rounded beam cavity disposed at or near a distal end of a beam line of the energy beam, transmitting a small portion of the beam energy through a ceramic window of the beam cavity into a waveguide coupled to the beam cavity at a position corresponding to an excitation mode of the beam cavity, measuring a signal from the waveguide with a processing unit and determining beam intensity or charge from the signal, and optionally, controlling the linear accelerator and / or associated components based on the determined beam intensity. Fig.10 A method for obtaining complete beam information using an advanced beam monitor as described above is provided. The method may include the steps of transmitting an accelerated energy beam generated by a linear accelerator into a rounded beam cavity along a beam line of the energy beam, wherein the beam cavity is elliptical, transmitting a small portion of the beam energy through a plurality of ceramic-filled openings into a plurality of waveguides coupled to the beam cavity at respective positions, each position corresponding to a different excitation mode of the beam cavity, measuring a plurality of signals from the plurality of waveguides with a processing unit, and determining beam charge, beam position and beam size from the plurality of signals, and optionally, controlling a linear accelerator beam generator based on the determined beam characteristics.

[0049] Fig.11 A portion 300 of a linear accelerator with an integrated beam monitor is shown in accordance with some embodiments. The linear accelerator body 301 is designed with a pair of off-axis beam monitor coupling ports 310 so that tuning of the beam monitor cavity can be performed from on-axis tuning pins or features 312. The beam monitor coupling ports can be an integral feature of the linear accelerator body.

[0050] As shown, the linear accelerator body can include a plurality of such tuning pins or features 312 corresponding to the plurality of cavities of the linear accelerator. These two ports allow the Q factor of the beam monitor to be reduced to any desired value, and thus control the amount of radiation received from one of the coupling ports. This control results in saving the external components required to attenuate the strong signal emitted from the beam monitor. On the other hand, if the current passing through is too small to generate an RF signal, the Q factor can be increased. In some embodiments, by measuring the phase of the signal output by the beam monitor and combining the phase with the linear accelerator simulation, one or more beam characteristics can be determined, such as estimating the energy of the beam. One or more tuning features 314 (e.g., tuning pins) are provided on the axis to allow the beam monitor cavity 316 to be tuned. Although two beam monitor ports are shown, it should be understood that such a linear accelerator system may include one or more off-axis beam monitor coupling ports and one or more tuning features on the axis.

[0051] Fig.12 A cross-sectional view 300' of a portion of a linear accelerator with an integrated beam monitor according to some embodiments is shown. A beam monitor coupling port 310 is disposed off the axis of a beam monitor cavity 316 and extends upward from the beam monitor cavity 316. In this embodiment, the system includes a pair of tuning features disposed on opposite sides of the beam monitor cavity and aligned with the beam cavity (e.g., on axis). The present invention may also include methods of making such a linear accelerator and methods of using such a linear accelerator.

[0052] The methods, systems, and devices discussed above are examples. Various configurations may omit, replace, or add various programs or components as appropriate. For example, in an optional configuration, the method may be performed in an order different from that described, and / or various stages may be added, omitted, and / or combined. In addition, features described with respect to certain configurations may be combined in various other configurations. Different aspects and elements of the configurations may be combined in a similar manner. And further, technology is constantly evolving, and some of the elements described are provided as non-limiting examples, and therefore do not limit the scope of the present disclosure or claims.

[0053] Specific details are given in the description to provide a thorough understanding of the exemplary configurations (including implementations). However, the configurations can be made without these specific details. For example, well-known circuits, processes, algorithms, structures, and techniques have been shown without unnecessary details to avoid obscuring the configurations. This description provides exemplary configurations that do not limit the scope, applicability, or configurations of the claims. Instead, the foregoing description of the configurations will provide those skilled in the art with an implementation description for implementing the described techniques.

[0054] In addition, the configuration can be described as a process, which is depicted as a flow chart or block diagram. Although each operation can be described as a continuous process, some operations can be performed in parallel or concurrently. In addition, examples of methods can be implemented by hardware, software, firmware, middleware, microcode, hardware description language, or any combination thereof. When implemented in software, firmware, middleware, or microcode, the program code or code segments for performing the necessary tasks can be stored in a non-transient computer readable medium, such as a storage medium. The processor can perform the described tasks.

[0055] Having described several exemplary configurations, various modifications, alternative structures, and equivalents may be used without departing from the spirit of the present disclosure. The above elements may be components of a larger system, in which other rules may take precedence over or modify the application of the present invention. Therefore, the above description does not limit the scope of the claims. All patents, patent applications, and other publications cited in this application are incorporated by reference in their entirety for all purposes.

Claims

1. A beam monitor for monitoring a beam from a linear accelerator, the beam monitor comprising: a body having a beam cavity defined therein and extending along an xy plane, wherein the beam cavity is generally rounded about a central axis extending in the z direction; an input in communication with the beam cavity, the input configured to transmit the accelerated beam into the beam cavity, the input having an input diameter; an output in communication with the beam cavity, the input being configured to transmit the accelerated energy beam out of the beam cavity, the output having an output diameter equal to or greater than the input diameter; wherein the input and the output extend from a center of the cavity along a z-axis perpendicular to the xy plane, the input and the output extending in opposite directions; one or more windows in the beam cavity, the one or more windows being disposed at locations of corresponding excitation modes of the beam cavity; as well as One or more waveguides coupled to the one or more windows, the one or more waveguides configured to measure one or more beam characteristics from one or more signals generated by beam energy transmitted into the one or more waveguides through the one or more windows of the beam cavity, wherein the one or more beam characteristics include any of: beam intensity, charge, current, size, position, emissivity, or any combination thereof.

2. The beam monitor according to claim 1, characterized in that The one or more beam characteristics include beam charge or intensity.

3. The beam monitor according to claim 2, characterized in that The window is arranged on the outer circumference of the beam cavity.

4. The beam monitor according to claim 1, characterized in that Each of the one or more windows includes a ceramic disposed in an opening.

5. The beam monitor according to claim 4, characterized in that Each of the plurality of waveguides comprises a rectangular waveguide.

6. The beam monitor according to claim 1, characterized in that Each of the plurality of waveguides is arranged according to the respective excitation mode, wherein each excitation mode corresponds to a beam characteristic.

7. The beam monitor according to claim 1, characterized in that The beam cavity, the input diameter, the output diameter, and the one or more windows are sized and arranged so that only a suitable portion of beam energy from the accelerated beam is transmitted through the one or more windows.

8. The beam monitor according to claim 7, characterized in that For beams of 3 MW or greater, the suitable fraction comprises 100 kW or less.

9. The beam monitor according to claim 7, characterized in that The beam cavity, the input diameter, the output diameter, and the one or more windows are sized such that 10% or less of beam energy from the accelerated beam is transmitted through the one or more windows.

10. The beam monitor according to claim 7, characterized in that The beam cavity, the input diameter, the output diameter, and the one or more windows are sized such that 3% or less of beam energy from the accelerated beam is transmitted through the one or more windows.

11. The beam monitor according to claim 1, wherein: The beam monitor is configured to measure one or more characteristics of the 9.3 GHz beam.

12. The beam monitor according to claim 1, wherein: The beam cavity is located at a distal end of a plurality of buncher cavities of the linear accelerator for accelerating the beam along the beam line, wherein a volume of the beam cavity is less than 25% of a volume of each of the plurality of buncher cavities.

13. The beam monitor of claim 1, wherein: The beam cavity is located at a distal end of a plurality of buncher cavities of the linear accelerator for accelerating the beam along the beam line, wherein a volume of the beam cavity is less than 10% of a volume of each of the plurality of buncher cavities.

14. The beam monitor of claim 1, wherein: The ratio of the radius to the height of the beam cavity is 4:

1.

15. The beam monitor of claim 1, wherein: The output diameter is at least four times the input diameter.

16. The beam monitor of claim 1, wherein: The body is a distal portion of the linear accelerator block, and the plurality of buncher cavities are formed in the distal portion.

17. The beam monitor of claim 1, wherein: The body is a separate component coupled to the distal end of the linear accelerator.

18. The beam monitor of claim 1, It is characterized in that The cavity is elliptical, the x-dimension of the cavity being greater than the y-dimension so as to separate modal frequencies of different polarizations of the beam cavity; a plurality of windows on the beam cavity; as well as A plurality of waveguides are coupled to the plurality of windows and are configured to measure a plurality of beam characteristics from a plurality of signals generated by beam energy transmitted through the plurality of windows into the plurality of waveguides, wherein the one or more beam characteristics include at least: beam charge, beam position, and beam size.

19. The beam monitor of claim 18, wherein: Each of the plurality of windows is located at a different position on the beam cavity, each position corresponding to a different excitation mode of the beam cavity.

20. The beam monitor of claim 18, wherein: The beam cavity includes at least five excitation modes and includes five waveguides coupled to the beam cavity.

21. The beam monitor of claim 20, wherein: The beam monitor is configured so that the five modes excited include TM 010 Mode, two TM 110 mode, and two TMs 210 model.

22. The beam monitor of claim 18, wherein: The plurality of waveguides include one waveguide and corresponding window on a periphery of the beam cavity, and two waveguides and corresponding windows on each of the opposing major faces of the beam cavity.

23. A linear accelerator system comprising: Linear accelerator; The beam monitor of claim 1, wherein the beam monitor is disposed at a distal end of the linear accelerator along the beam line; A processing unit having a memory having programmable instructions recorded thereon, the instructions being configured to: obtaining a plurality of signals from each of the one or more waveguides; as well as One or more beam characteristics are determined based on the one or more signals from the one or more waveguides.

24. The system of claim 23, wherein: The one or more beam characteristics include at least beam charge, beam position, and beam size.

25. The system of claim 23, further comprising: A control unit is communicatively coupled to the processing unit, the control unit being configured to control the linear accelerator and to modify control and / or adjust positioning of the beam in response to the one or more beam characteristics determined by the processing unit.

26. A method of monitoring a beam from a linear accelerator, the method comprising: transmitting an accelerated energy beam generated by the linear accelerator into a rounded beam cavity disposed at a distal end of a beamline of the energy beam; transmitting a portion of the beam energy through a ceramic window of the beam cavity into a waveguide coupled to the beam cavity at a location corresponding to an excitation mode of the beam cavity; measuring, with a processing unit, a signal from the waveguide; as well as The beam intensity or charge is determined from the signal.

27. The method of claim 26, wherein: The beam cavity is cylindrical and the waveguide is rectangular, wherein the waveguide is attached to a periphery of the cylindrical beam cavity.

28. The method of claim 26, wherein: For a 3 MW beam, the portion comprises 100 kW or less.

29. The method of claim 26, wherein: The linear accelerator is 9.3 GHz.

30. The method of claim 26, wherein: The linear accelerator and / or associated components are controlled based on the determined beam intensity.

31. A method for monitoring beam characteristics, the method comprising: transmitting an accelerated energy beam generated by a linear accelerator into a rounded beam cavity along a beam line of the energy beam, wherein the beam cavity is elliptical; transmitting a portion of the beam energy through a plurality of ceramic-filled openings into a plurality of waveguides coupled to the beam cavity at different locations, each location corresponding to a different excitation mode of the beam cavity; measuring, with a processing unit, a plurality of signals from the plurality of waveguides; A plurality of beam characteristics are determined based on the plurality of signals, the plurality of beam characteristics including at least: beam charge, beam position, and beam size.

32. The method of claim 31, wherein: The plurality of waveguides includes five waveguides, one waveguide extending from a periphery of the beam cavity and two waveguides extending from each of the opposing major faces of the beam cavity.

33. The method of claim 32, wherein: The plurality of signals from the five waveguides are used to determine the beam charge, the beam position in the x-direction and the y-direction, and the beam size in the x-direction and the y-direction.

34. The method of claim 31, wherein: The linear accelerator beam generator is controlled based on the determined beam characteristics.

35. The method of claim 34, wherein: Controlling includes adjusting positioning of the beam based on the determined beam position.

36. A linear accelerator comprising: a linear accelerator body having a plurality of cavities; one or more beam monitor coupling ports coupled to and disposed off-axis from the respective cavities such that one or more beam characteristics may be determined from measurements via the one or more beam monitor coupling ports; as well as One or more tuning features are disposed adjacent to and on an axis of the respective cavity to facilitate tuning of the cavity using the tuning features.

37. The linear accelerator of claim 36, wherein: The one or more tuning features include a pair of tuning pins disposed on opposite sides of the cavity.

38. The linear accelerator of claim 36, wherein: The linear accelerator includes two beam monitor coupling ports coupled to the respective cavities to allow the Q factor of the beam monitor cavity to be reduced to any desired value and to control the amount of radiation received by each port.

39. The linear accelerator of claim 36, wherein: The one or more beam monitoring coupling ports and the corresponding cavity are integrated within the linear accelerator body.

40. A method of forming the linear accelerator body of claim 36.

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