Radio frequency source, linear accelerator system and method for operating a radio frequency source

Abstract

The invention relates to a radio frequency source for a linac system, a linac system, a method for operating a radio frequency source and a computer program product therefor. The radio frequency source for a linac system according to the invention has a microwave generator for generating microwaves, an adjustment unit and a circulator having a ferrite for isolating the microwave generator from backscattered microwaves by influencing the phase of the microwaves in accordance with a magnetic field, characterized in that the circulator has an electrical phase stabilization element, wherein the adjustment unit is designed to receive a measured variable describing the magnetic permeability of the circulator and to set an electrical current and / or voltage to the electrical phase stabilization element for influencing the magnetic field in accordance with the received measured variable such that an amplitude difference between the generated microwaves and the backscattered microwaves is maximized.

Description

Technical Field

[0001] The present invention relates to a radio frequency source for a linear accelerator system, a linear accelerator system, a method for operating the radio frequency source, and an associated computer program product. Background Technology

[0002] Radio frequency (RF) sources are typically used to provide radio frequency microwaves, which are used, for example, to accelerate charged particles, particularly electrons, in conventional linear accelerator systems. Such RF sources for linear accelerators are known, for example, from DE 10 2012 209 185 A1.

[0003] Linear accelerator systems provide high-energy charged particles or MeV photons, particularly MeV X-ray radiation, depending on the application. These MeV photons are typically generated through the interaction of charged particles with a target within a linear accelerator unit. For example, linear accelerator systems are used in customs inspection and / or materials inspection. In principle, their use in radiotherapy and / or medical imaging is conceivable and known.

[0004] Such a linear accelerator system typically comprises two of three main components that work together in a conventional manner within the device. The first main component is the linear accelerator unit. The other main component is a supply module, which is configured to provide and / or open-loop and / or closed-loop control the voltages and / or currents required for the (other) main components, and includes, for example, an radio frequency source. The third main component is a cooling system, referred to as, for example, a "chiller".

[0005] Cooling systems are commonly used for temperature stabilization of radio frequency (RF) sources, particularly the circulators of RF sources. Temperature stabilization specifically implies temperature control. Cooling systems are especially temperature control systems. Cooling systems provide cooling or heating power for temperature stabilization. Temperature stabilization specifically includes temperature control, i.e., cooling and / or heating. Without temperature stabilization, temperature changes typically result in additional phase shifts in the ferrite of the circulator. Additional phase shifts typically detrimental to the isolation of the microwave generator relative to backscattered microwaves. Isolation typically requires the generated microwaves to have a specific phase relative to the backscattered microwaves.

[0006] Such conventional cooling systems typically require approximately one-third to one-half of the equipment's structural space and one-third to one-half of its electrical power consumption. This demand for structural space and / or electrical power generally increases the environmental requirements for housing the equipment. The operational demands on conventional equipment are correspondingly higher, especially when the equipment is used on a mobile platform. The mobile platform can, for example, be part of a cargo vehicle.

[0007] If the environment housing the device does not fully meet the requirements, the device typically operates with reduced beam performance. Reduced beam performance allows for a reduction in the cooling power of the cooling system and thus a reduction in structural space and / or electrical power requirements. Alternatively or additionally, the device, particularly the cooling system, can traditionally be designed to be smaller by sharing a portion of its cooling power with another existing cooling system. However, this other existing cooling system requires robust system integration and / or connectivity with other systems, which typically increases the complexity of the device. Summary of the Invention

[0008] The purpose of this invention is to provide a radio frequency source for a linear accelerator system with an improved temperature operating range, a linear accelerator system, a method for operating the radio frequency source, and related computer program products.

[0009] The objective is achieved through features of the embodiments. Advantageous design solutions are described below.

[0010] The radio frequency source for a linear accelerator system according to the present invention has:

[0011] - A microwave generator used to generate microwaves.

[0012] - Adjustment unit, and

[0013] - A circulator having ferrite for isolating a microwave generator relative to backscattered microwaves by influencing the phase of the microwaves according to the magnetic field.

[0014] Its features are,

[0015] The circulator has an electrical phase stabilizing element.

[0016] The adjustment unit is configured to receive a measurement variable describing the permeability of the circulator and to set the current and / or voltage of the electric phase stabilizing element to influence the magnetic field according to the received measurement variable.

[0017] This maximizes the amplitude difference between the generated microwaves and the backscattered microwaves.

[0018] The method for operating a radio frequency source according to the present invention comprises the following steps:

[0019] - The adjustment unit receives a measurement variable describing the permeability of the circulator.

[0020] - The current and / or voltage of the electric phase stabilizing element are set by means of the adjustment unit to influence the magnetic field according to the measured variables, so as to maximize the amplitude difference between the generated microwave and the backscattered microwave.

[0021] Methods for operating radio frequency (RF) sources generally include open-loop or closed-loop control of the RF source.

[0022] One advantage of this operation of the radio frequency (RF) source is that, compared to conventional RF sources, the RF source according to the invention advantageously requires significantly less structural space and / or electrical power. This advantage is achieved, for example, by having an electrical phase-stabilizing element in the RF source actively resist temperature fluctuations, which in particular cause changes in permeability and, therefore especially, the phase of microwaves.

[0023] The radio frequency (RF) source preferably compensates for or completely eliminates the cooling power by actively closed-loop controlling an electrical phase stabilizing element. This cooling power is typically used for temperature stabilization of the RF source. The compensation particularly includes electrothermal compensation and / or electromagnetic compensation.

[0024] Microwave generators typically include magnetrons or klystrons. A high voltage is typically applied at the input of the microwave generator, which is then converted at the output side into radio frequency microwaves with a power associated with that voltage. The microwave generator produces alternating electromagnetic fields in the GHz range, particularly between 1 GHz and 10 GHz, and preferably between 2 GHz and 4 GHz. The generated microwaves are particularly suitable for accelerating charged particles.

[0025] The generated microwaves are defined as microwaves produced by a microwave generator. Generated microwaves are particularly forward-directed microwaves. Backscattered microwaves are particularly backward-directed microwaves. Backscattered microwaves are especially found at the payload of a circulator, for example in a linear accelerator system and / or the circulator itself, particularly according to the generated microwaves.

[0026] The circulator typically has at least three ports, with a first port connectable to a microwave generator, a second port connectable to a payload, particularly a linear accelerator unit in a linear accelerator system, and a third port connectable to a load, particularly for absorbing backscattered microwaves. Such a three-port circulator is typically Y-shaped, with the legs offset by 120°. It is conceivable, in principle, that the circulator may have a fourth port, which could, for example, be connected to a reflective phase shifter or other load. In operation, the circulator is typically connected at the respective ports, for example, via hollow conductors. The load and / or other loads may, in particular, be water loads.

[0027] Circulators, especially ferrite circulators, are used. A circulator contains ferrite material arranged and configured such that the generated microwaves and backscattered microwaves are separated from each other and / or the backscattered microwaves do not return to the microwave generator. To magnetize the ferrite, the circulator typically has another permanent magnet. The ferrite can thus function particularly as an insulator because it is subjected to a magnetic field.

[0028] Advantageously, the frequency domain of the microwaves to be separated in the circulator can be adjusted by means of a regulating unit. Due to the electrical phase stabilizing element, the circulator is advantageously a substantially temperature-independent circulator. The circulator of the RF source preferably has a larger operating temperature range than conventional circulators because the electrical phase stabilizing element can compensate for temperature fluctuations. The operating temperature range of the circulator is particularly at least ±2°C, preferably at least ±5°C, advantageously at least ±20°C, and particularly advantageously at least ±50°C. Preferred operating temperatures of the circulator are, for example, 30°C, 40°C, 60°C, or 80°C, and fall within the corresponding operating temperature range. The ±°C operating temperature range is, for example, related to the operating temperature and is not necessarily related to 0°C. Within the operating temperature range, the RF source, especially the circulator, can operate optimally, preferably sufficiently well. Within the operating temperature range, i.e., from the lower limit to the upper limit, the microwaves passing through the circulator preferably have substantially the same phase through closed-loop control by means of the electrical phase stabilizing element.

[0029] The adjustment unit may be a calculation unit or part of a calculation unit. The adjustment unit particularly has an input interface for receiving a measured variable. The measured variable particularly reflects the magnitude of the permeability. The measured variable may be vector-based. The measured variable may particularly be time-resolved. The adjustment unit is particularly configured to initiate or trigger a measurement using a measuring device. The adjustment unit can trigger measurements multiple times. Measurements may be performed periodically and / or continuously.

[0030] The regulating unit may be part of the measuring device or connected to the measuring device via wired or wireless means. The regulating unit may, in particular, receive measured variables via an input interface, store the measured variables in a buffer storage unit, and / or process the measured variables during setting. Processing is particularly based on logic and / or algorithms. Processing may particularly be based on a program code mechanism describing the logic and / or algorithm. Processing may be performed digitally and / or analogously. Processing may particularly be repeated. Processing of the measured variables is particularly important when setting the current and / or voltage of the phase stabilizing element, for example, after the measured variables have been received and / or stored in the buffer storage unit.

[0031] Setting the current and / or voltage specifically includes processing the measured variables and / or determining a regulation value. The determined regulation value can be applied to the output interface of the regulating unit. Alternatively or additionally, the regulating unit can be configured to apply current and / or voltage to an electrical phase stabilizing element by means of the determined regulation value.

[0032] The current and / or voltage settings are performed multiple times, preferably periodically and / or continuously, particularly according to logic and / or algorithms. The settings specifically represent solving an optimization problem aimed at maximizing the amplitude difference and / or minimizing the RF power of the backscattered microwaves. The logic and / or algorithms are particularly designed to make the amplitude difference either maximum or maximum. In other words, the settings can be performed multiple times until the amplitude difference is maximized. The settings may result in the amplitude difference becoming smaller compared to previous amplitude differences. The adjustment unit advantageously corrects for the smaller amplitude difference by means of subsequent settings.

[0033] The maximum amplitude difference particularly signifies the circulator's ability to isolate itself during operation of the RF source. In other words, the circulator's isolation capability during operation is ensured by an electrical phase stabilizing element. The circulator's isolation capability depends especially on the magnetic field provided at the ferrite and the temperature of the ferrite.

[0034] The largest amplitude difference specifically means that the RF power transmitted by the generated microwave is substantially greater than the RF power transmitted by the backscattered microwave. Insertion loss Advantageously less than 1 dB. The attenuation in the backward direction is particularly high, exceeding 20 dB, and preferably higher than 30 dB. The maximum amplitude difference typically means the minimum RF power of the backscattered microwaves.

[0035] The magnitude of the maximum amplitude difference can vary, in particular, according to the time of measurement of the measured variable. Radio frequency (RF) sources, for example, in the form of microwaves with specific pulse lengths, provide RF power in a manner that is within the upper time limit. At the beginning of the pulse, the RF power of the backscattered microwave is typically greater than that of the backscattered microwave in steady state.

[0036] The setting of current and / or voltage specifically includes closed-loop control of the phase stabilizing element. This setting, in particular, causes the measured variables to affect the magnetic field by means of the phase stabilizing element. This setting, in particular, enables compensation for undesirable permeability deviations and thus magnetic field deviations. The set current and / or set voltage directly affect the magnetic field at the ferrite in the circulator. The phase stabilizing element may have an input interface for receiving the adjusted values.

[0037] The phase stabilizing element is particularly a part of a circulator. The phase stabilizing element consumes electrical power according to a set current and / or a set voltage. The phase stabilizing element is particularly in direct physical contact with the circulator. The phase stabilizing element is fixedly connected and / or coupled to the circulator. The phase stabilizing element acts according to a set current and / or voltage, particularly in close proximity to the circulator and / or in close proximity to or at the ferrite. The phase stabilizing element influences the magnetic field, for example, by means of the superposition of one magnetic field with another and / or the influence of the permeability of the ferrite. The influence of the magnetic field includes, in particular, changes in the magnitude and / or orientation of the magnetic field.

[0038] One embodiment proposes that the electric phase stabilizing element for influencing the magnetic field has an adjustable sensing element that is induced by a set current and / or a set voltage. In this embodiment, the magnetic field provided at the ferrite is superimposed on an additional magnetic field from the sensing element. This embodiment is particularly advantageous because the magnetic field is directly adjusted, which can typically be done relatively quickly.

[0039] One embodiment proposes that the sensing element has at least one electromagnetic coil. The at least one electromagnetic coil is advantageously capable of precisely influencing the magnetic field by applying a predetermined current and / or a predetermined voltage. The at least one electromagnetic coil is, for example, located at one of the ferrite particles. Additionally, another electromagnetic coil may be located at another ferrite particle. The arrangement of the ferrite particles and the at least one electromagnetic coil is typically symmetrical. For example, the coil is made of copper.

[0040] One embodiment proposes that the electrical phase stabilizing element additionally includes a permanent magnet, around which at least one electromagnetic coil is wound. Alternatively, the electromagnetic coil may be wound around another permanent magnet. The at least one electromagnetic coil and the permanent magnet or the other permanent magnet particularly form a particularly advantageous adjustable magnet for influencing the magnetic field. To close the magnetic circuit, a U-shaped yoke may be arranged around the at least one electromagnetic coil and around the permanent magnet or the other permanent magnet.

[0041] One embodiment proposes that the electric phase stabilizing element for influencing the magnetic field has an adjustable thermoelectric component that carries a set current and / or a set voltage for closed-loop control of the temperature within the circulator. This embodiment particularly utilizes the physical effect of the temperature dependence of the circulator's isolation capability, where temperature in turn affects the permeability. For example, if a measured variable indicates a relatively low isolation capability, the isolation capability can be partially, preferably fully, or maximally restored by controlling the temperature in a closed loop. The thermoelectric component advantageously enables closed-loop temperature control of the circulator. The thermoelectric component is typically directly thermally coupled to the circulator, particularly to ferrite. In principle, a heat transfer element, such as a cooling body and / or a gaseous or fluid-based cooling circulation loop, is conceivable between the thermoelectric component and the circulator.

[0042] One embodiment proposes that the thermoelectric component is a thermoelectric converter, particularly a Peltier element. The thermoelectric converter enables precise closed-loop control of the circulator's temperature, particularly that of a ferrite element, based on a set current and / or a set voltage.

[0043] One embodiment proposes that the radio frequency source has a measuring device for measuring electromagnetic variables of backscattered microwaves, wherein the electromagnetic variables are measuring variables describing the permeability of the circulator.

[0044] One implementation proposes that an electromagnetic variable describes the amplitude and / or phase of the backscattered microwave. The electromagnetic variable can be correlated or normalized, in particular, with respect to the electromagnetic variable of the generated microwave. For example, it is conceivable to calculate the amplitude difference and / or phase difference between the generated microwave and the backscattered microwave. The adjustment unit is particularly configured to compare the electromagnetic variable, for example, with a desired value. The desired value can be a constant value or can depend on the magnetic field. For example, if the electromagnetic variable describes the phase of the backscattered microwave, the desired value can be a value between 0 and 2π. If the electromagnetic variable describes the amplitude of the backscattered microwave, the desired value can be a value, in particular, a parabolic function, higher than the magnitude of the magnetic field.

[0045] One embodiment proposes a directional coupler between the measuring device and the circulator for separating the generated microwaves and the backscattered microwaves. This embodiment advantageously allows for separate consideration of the generated microwaves and the backscattered microwaves.

[0046] The linear accelerator system according to the invention comprises a radio frequency source and a linear accelerator unit, wherein the linear accelerator unit has a particle emitter for emitting charged particles, particularly electrons, and a cavity for accelerating charged particles, particularly electrons, by means of microwaves. The linear accelerator system according to the invention has the radio frequency source according to the invention and thus shares the aforementioned advantages. The linear accelerator system is particularly suitable for radiotherapy, materials inspection, and / or security inspection.

[0047] Linear accelerator systems are particularly used to accelerate charged particles, especially electrons, along a straight line. Charged particles are accelerated to energies above 1 MeV and typically below 20 MeV, for example, in the range of 3 MeV to 9 MeV, by means of a radio frequency source.

[0048] Particle emitters can be, in particular, electron emitters. Electron emitters can be thermionic emitters, such as helical emitters or spherical emitters, or cold emitters, such as those with carbon nanotubes or made of silicon. Electron emitters can have a grid for regulating electron injection.

[0049] The cavity, especially the linear accelerator cavity, is typically evacuated. The cavity particularly forms a standing wave accelerator or a traveling wave accelerator. The cavities are typically connected to each other and arranged in rows, such that charged particles pass through the cavities sequentially. A particle emitter is usually located at one end of the rows of cavities, while an exit opening is typically located at the other end. The exit opening can be closed using a vacuum-sealed window.

[0050] One embodiment proposes that the linear accelerator unit has a target disposed within the cavity for generating MeV X-ray radiation based on the accelerated charged particles. The target is typically disposed at the end of a cavity arranged in rows opposite to the particle emitter. The target may, for example, be part of an exit opening, and the exit opening is vacuum-sealed. The target is particularly a transport target. Charged particles typically impact the surface of the target at a perpendicular angle. The target typically has a disk shape. A disk is a cylinder whose height is generally smaller than its diameter. The target is particularly made of a material having a high atomic number (nuclear charge, Z) and / or high density, such as silver, copper, gold, aluminum, rhodium, tungsten, molybdenum, rhenium, zirconium, chromium, cobalt, iron, manganese, vanadium, titanium, tantalum, indium, iridium, or beryllium, or alloys of the aforementioned conventional target materials. The target material may particularly be tungsten. The target advantageously contains, for example, rhenium in addition to tungsten, making the target more robust and therefore stronger. The target may be in contact with a cooling medium on the side facing away from the electron beam.

[0051] For example, a linear accelerator system with an radio frequency (RF) source can be used either stationary or mobile. The linear accelerator system can advantageously operate without a dedicated cooling system or with a cooling system having relatively low cooling power. The linear accelerator system and / or the RF source can preferably be passively cooled.

[0052] The computer program product can be a computer program or include a computer program. The computer program product particularly has a program code structure reflecting the method steps according to the invention. Thus, the method according to the invention can be performed in a defined and repeatable manner, as well as control over the forwarding of information according to the method. The computer program product is preferably configured such that a computing unit can perform the method steps according to the invention by means of the computer program product. The program code structure can in particular be loaded into the memory of the computing unit and typically executed by means of the processor of the computing unit through access to the memory. When the computer program product, especially the program code structure, is executed in the computing unit, all the methods described according to embodiments of the invention can typically be performed. The computer program product is, for example, stored on a physical computer-readable medium and / or stored in a computer network in digital form as data packets. The computer program product can be a physical computer-readable medium and / or a data packet in a computer network. Therefore, the invention can also be based on a physical computer-readable medium and / or a data packet in a computer network. Physical computer-readable media can typically be directly connected to the computing unit, for example, by inserting the physical computer-readable media into a DVD drive or plugging it into a USB port, thereby allowing the computing unit to readably access the physical computer-readable media. Data packets are preferably accessible from a computer network. The computer network can have the computing unit or be indirectly connected to the computing unit via a wide area network (WAN) or (wireless) local area network (WLAN or LAN) connection. For example, a computer program product can be digitally stored at a storage location on the computer network on a cloud server and transmitted to the computing unit via the Internet via a WAN and / or via a WLAN or LAN, particularly by invoking a download link pointing to the storage location of the computer program product.

[0053] Features, advantages, or alternative embodiments mentioned in the description of the device can also be applied to the method, and vice versa. In other words, claims relating to the method can be modified by means of features of the device, and vice versa. The device according to the invention can be used in the method in particular. Attached Figure Description

[0054] The invention is described and illustrated below with reference to embodiments shown in the accompanying drawings. In principle, the same structures and units are retained in the following description of the drawings and named using the same reference numerals as when the corresponding structures or units first appear.

[0055] The attached diagram shows:

[0056] Figure 1 A radio frequency source according to the present invention is shown.

[0057] Figure 2A first embodiment of the radio frequency source is shown.

[0058] Figure 3 A second embodiment of the radio frequency source is shown.

[0059] Figure 4 A linear accelerator system with a 3-port circulator according to the present invention is shown.

[0060] Figure 5 A linear accelerator system with a 4-port circulator according to the present invention is shown.

[0061] Figure 6 The method according to the invention is shown.

[0062] Figure 7 An exemplary curve showing the variation of radio frequency power is shown.

[0063] Figure 8 The first conditioning circuit of the radio frequency source is shown.

[0064] Figure 9 The second regulation circuit of the radio frequency source is shown.

[0065] Figure 10 A third embodiment of the radio frequency source is shown.

[0066] Figure 11 A fourth embodiment of the radio frequency source is shown, and

[0067] Figure 12 The fifth embodiment of the radio frequency source is shown. Detailed Implementation

[0068] Figure 1 A schematic block diagram illustrates the radio frequency source 10 according to the present invention.

[0069] Radio frequency source 10 constitutes a linear accelerator system (not shown). Radio frequency source 10 includes a microwave generator 11 for generating microwaves, a modulation unit 12, and a circulator 13. Modulation unit 12 is configured to receive a measurement variable describing the permeability of the circulator 13.

[0070] Circulator 13 is in Figure 1 The figure shows a Y-shaped ferrite three-port circulator and a ferrite 13.F for isolating the microwave generator 11 relative to backscattered microwaves by influencing the phase of the microwaves according to the magnetic field 13.B. The magnetic field 13.B is drawn purely for illustrative purposes. Figure 1 The circulator 13 is indicated by a dashed directed arrow. It also has an electrical phase stabilizing element 14. A microwave generator 11 is connected to the circulator 13, but in this embodiment, no effective load or load is connected.

[0071] The control unit 12 is configured to set the current and / or voltage of the electric phase stabilizing element 14 to influence the magnetic field 13.B according to the received measurement variables, so that the amplitude difference between the generated microwave and the backscattered microwave is maximized.

[0072] Figure 2 A first embodiment of the radio frequency source 10 according to the present invention is shown. Figure 2 The central cross-section of the circulator 13 is shown in the figure.

[0073] In order to influence the magnetic field 13.B, the electric phase stabilizing element 14 has an adjustable sensing element 15 that is energized by a set current and / or a set voltage. The sensing element 15 has at least one electromagnetic coil 15.S. The electric phase stabilizing element 14 additionally has a permanent magnet 15.P, around which at least one electromagnetic coil 15.S is wound. Figure 2 As shown, two coils 15.S are wound around a permanent magnet 15.P, respectively. The induction element 15 surrounds the cavity 13.H and ferrite 13.F of the circulator 13. The ferrite 13.F is advantageously positioned between the two coils 15.S. The magnetic circuit specifically includes a yoke 13.J, at least one electromagnetic coil 15.S, the permanent magnet 15.P, the ferrite 13.F, and the gap in the cavity 13.H.

[0074] Figure 3 A second embodiment of the radio frequency source 10 according to the present invention is shown. This embodiment can be clearly compared with... Figure 2 The embodiments shown are combinations thereof.

[0075] To influence the magnetic field 13.B, the electric phase stabilizing element 14 has an adjustable thermoelectric component 16 for regulating the temperature within the circulator 13, which is shaped by a set current and / or a set voltage. Thermoelectric component 16 is a thermoelectric converter, particularly a Peltier element 16.P. Figure 3 In this context, the Peltier element 16.P is characterized by a snowflake because the thermoelectric component 16 regulates the temperature within the circulator 13 according to a set current and / or a set voltage.

[0076] exist Figure 3 The diagram also shows that the radio frequency source 10 has a measuring device 17 for measuring electromagnetic variables of backscattered microwaves, wherein the electromagnetic variables are measured variables describing the permeability of the circulator 13. The electromagnetic variables describe the amplitude and / or phase of the backscattered microwaves. The measuring device 17 is connected to the adjustment unit 12 for transmitting the measured variables.

[0077] Figure 4A block diagram of a linear accelerator system 20 with a three-port circulator according to the present invention is shown. The linear accelerator system 20 according to the present invention includes a radio frequency source 10 and a linear accelerator unit 21. The linear accelerator unit 21 has a particle emitter for emitting charged particles and a cavity for accelerating charged particles by means of microwaves. The circulator 13 is configured as a three-port circulator, wherein a microwave generator 11 is connected to a first port, the linear accelerator unit 21 is connected to a second port, and a load 13.L is connected to a third port.

[0078] Figure 5 A block diagram of a linear accelerator system 20 with a 4-port circulator according to the present invention is shown. Figure 4 Compared to the illustrated embodiment, a reflective phase shifter 19, which is part of the radio frequency source 10, is connected to an additional port of the circulator 13. Alternatively, another load may be connected instead of the reflective phase shifter 19. The linear accelerator unit 21 in this embodiment has a target disposed within the cavity for generating MeV X-ray radiation based on the accelerated charged particles.

[0079] Figure 5 It is also shown that a directional coupler 18 for separating the generated microwaves and backscattered microwaves is provided between the measuring device 17 and the circulator 13.

[0080] Figure 6 A flowchart is shown for a method for operating a radio frequency source 10 according to the present invention.

[0081] Method step S100 means that the adjustment unit 12 receives a measurement variable describing the permeability of the circulator 13.

[0082] Method step S101 means that the current and / or voltage of the electric phase stabilizing element 14 are set by means of the adjustment unit 12 so as to affect the magnetic field according to the measured variables, so as to maximize the amplitude difference between the generated microwave and the backscattered microwave.

[0083] Figure 7 The diagram shows the time-varying power of the generated microwave (L1, dashed line) and the backscattered microwave (L2, dotted line) in an exemplary time interval, with a linear accelerator unit connected as the payload.

[0084] The first rise of L2 typically begins directly from the beginning of pulse L1, and is especially a result of the RF power being reflected off the "empty" linear accelerator unit. Therefore, there are no charged particles in the cavity yet. When the linear accelerator unit acts as a type of RF source for a short time, the second rise of L2 typically begins from the end of pulse L1.

[0085] At time T1, i.e. at the beginning of the pulse of the generated microwave L1, the measurement variable of the backscattered microwave is independent of the frequency adaptation of the microwave generator 11 to the linear accelerator unit 21 in a first approximation, and is dominated by the scattering of the generated microwave.

[0086] At time T2, the RF source 10 is in a steady state, typically after the microwave generator 11 has been frequency-matched to the linear accelerator unit 21. The measurement variables of the backscattered microwaves are dominated by the input reflection of the circulator 13.

[0087] The regulating loop shown in the figure below can basically operate at two times, T1 and T2.

[0088] Figure 8 The first regulation circuit of the radio frequency source 10 is shown.

[0089] The backscattered microwave L2 is coupled out from the circulator 13 via a directional coupler 18 and measured by a measuring device 17 to determine a measurement variable. The measurement variable is transmitted to an adjustment unit 12, which continuously or clock-controlledly sets the current and / or voltage of the phase stabilizing element 14 to minimize the amplitude of the backscattered microwave L2, thereby maximizing the amplitude difference between the generated microwave and the backscattered microwave. The phase stabilizing element 14 has a sensing element 15 for this purpose.

[0090] Figure 9 The second regulation circuit of the radio frequency source 10 is shown.

[0091] Compared to the first loop, the measuring device 17 measures the generated microwave L1 and the backscattered microwave L2 to determine the measurement variables describing the phase difference in the stated case. The adjustment unit 12 sets the current and / or voltage of the electrical phase stabilizing element 14 such that the phase difference substantially corresponds to the desired value.

[0092] Figure 10 and Figure 11 The third and fourth embodiments of the radio frequency source 10 with a Peltier element 16.P are partially shown. These two embodiments are essentially based on... Figure 2 In one embodiment, the thermoelectric component 16 is used for closed-loop control of the temperature within the circulator 13.

[0093] exist Figure 10 In this configuration, the Peltier element 16.P is directly thermally coupled to the cooling system 22, which has relatively low cooling power, for temperature stabilization. The coupling between the Peltier element 16.P and the cooling system 22 can be achieved by means of a cooling body (not shown). The circulator 13 is directly thermally coupled to the thermoelectric component 16. The cooling system 22 has a first cooling circulation loop, which includes a heat exchanger 23, a heating device 24, a pump 25, a distributor 26, and a collector 27.

[0094] and Figure 10 Compared to the embodiments shown, Figure 11 The circulator 13 is shown to be directly thermally coupled to the Peltier element 16.P via an intermediate cooling circulation loop 28 for temperature stabilization.

[0095] Figure 12 A fifth embodiment of the radio frequency source 10 is shown. Compared to the embodiment with thermoelectric components 16, the cooling system 22 is directly thermally coupled to the circulator 13. The cooling system 22 therefore directly cools the circulator 13. The sensing component 15 compensates for the larger operating temperature range due to the relatively low cooling power, particularly by influencing the magnetic field.

[0096] Although the present invention has been illustrated and described in detail with reference to preferred embodiments, the present invention is not limited to the disclosed examples and other variations can be derived by those skilled in the art without departing from the scope of protection of the present invention.

Claims

1. A radio frequency source (10) for a linear accelerator system (20), the radio frequency source (10) having: - A microwave generator (11) for generating microwaves, - Adjustment unit (12), and - A circulator (13) having ferrite (13.F) for isolating the microwave generator (11) relative to backscattered microwaves by influencing the phase of the microwaves according to a magnetic field (13.B). The circulator (13) described therein has an electrical phase stabilizing element (14), in, The adjustment unit (12) is configured to receive a measurement variable describing the permeability of the circulator (13) and to set the current and / or voltage of the electric phase stabilizing element (14) to influence the magnetic field (13.B) according to the received measurement variable. The amplitude difference between the generated microwaves and the backscattered microwaves is the largest. Its distinguishing feature is that it includes a measuring device (17) for measuring the electromagnetic variables of the backscattered microwaves. The electromagnetic variable mentioned above is a measurement variable describing the permeability of the circulator (13). The electromagnetic variables described therein describe the amplitude and / or phase of the backscattered microwaves.

2. The radio frequency source (10) according to claim 1, In order to influence the magnetic field (13.B), the electric phase stabilizing element (14) has an adjustable sensing element (15) that is induced by a set current and / or a set voltage.

3. The radio frequency source (10) according to claim 2, The sensing element (15) has at least one electromagnetic coil (15.S).

4. The radio frequency source (10) according to claim 3, The electric phase stabilizing element (14) additionally has a permanent magnet (15.P), and the at least one electromagnetic coil (15.S) is wound around the permanent magnet (15.P).

5. The radio frequency source (10) according to any one of claims 1 to 4, In order to influence the magnetic field (13.B), the electric phase stabilizing element (14) has an adjustable thermoelectric component (16) for regulating the temperature inside the circulator (13) by a set current and / or a set voltage.

6. The radio frequency source (10) according to claim 5, The thermoelectric component (16) is an electrothermal converter.

7. The radio frequency source (10) according to claim 1, A directional coupler (18) for separating the generated microwaves and the backscattered microwaves is provided between the measuring device (17) and the circulator (13).

8. The radio frequency source (10) according to claim 5, The thermoelectric component (16) is a Peltier element (16.P).

9. A linear accelerator system (20), the linear accelerator system (20) having: - The radio frequency source (10) according to any one of claims 1 to 8, and - A linear accelerator unit (21) having a particle emitter for emitting charged particles and a cavity for accelerating the charged particles by means of microwaves.

10. The linear accelerator system (20) according to claim 9, The linear accelerator unit (21) has a target disposed within the cavity for generating MeV of X-ray radiation based on the accelerated charged particles.

11. A method for operating a radio frequency source (10) according to any one of claims 1 to 8, the method comprising the steps of: - The adjustment unit (12) receives a measurement variable describing the permeability of the circulator (13). - The current and / or voltage of the electrical phase stabilizing element (14) are set by means of the adjustment unit (12) to influence the magnetic field according to the measured variables, so that the amplitude difference between the generated microwave and the backscattered microwave is maximized.

12. A computer program product capable of being directly loaded into the memory of an adjustment unit, the computer program product having a program code structure so as to perform the method according to claim 11 when the computer program product is executed in the adjustment unit.

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