Linear accelerator joint

Abstract

The present disclosure discloses a reusable joint for a medical linear accelerator, a reusable CF choke flange for a medical linear accelerator, a linear accelerator, and a method of forming a reusable joint for a medical linear accelerator. The reusable joint includes a CF choke flange, a CF cover flange, and a gasket. The CF choke flange includes a first waveguide slot, a choke groove, and a first CF groove including a first knife edge, wherein the choke groove is disposed radially inward from the first CF groove on the CF choke flange. The CF cover flange includes a second waveguide slot aligned with the first waveguide slot and a second CF groove including a second knife edge and aligned with the first CF groove. The gasket is disposed between and in contact with the first CF groove and the second CF groove.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to radiotherapy devices, and in particular to radiotherapy devices comprising a linac and a linac adapter. BACKGROUND

[0002] Radiotherapy can be described as the use of ionizing radiation, such as X-rays, to treat a human or animal body. Radiotherapy is often used to treat a tumor within a patient or subject. In such treatment, ionizing radiation is used to irradiate, and thus destroy or damage, cells forming part of the tumor.

[0003] Radiotherapy devices typically include a gantry supporting a beam generating system or other radiation source, which can be rotated about a patient. For example, for a linac device, the beam generating system can include a radiofrequency energy source, an electron source, an acceleration waveguide, a beam shaping device, etc.

[0004] In high power radiofrequency (RF) systems, arcing can occur due to defects in the interior surface of the RF waveguide. Arcing can be described as a discharge or power breakdown, and can damage the expensive RF power source and other components of the RF system. In a typical linear accelerator, such as an ultra-high vacuum (UHV) linac, the individual segments of the acceleration waveguide are brazed or welded together to present a relatively smooth and continuous surface inside the waveguide for the radiofrequency (RF) wave to propagate. This can limit arcing. However, such brazed or welded connections are permanent connections, meaning that the individual segments of the waveguide cannot be separated after brazing or welding without destroying or damaging the connections and / or individual segments of the waveguide. Thus, replacing / repairing damaged components (e.g., a target, an electron (particle) source such as an electron gun, and an RF window) would be difficult. Instead, a failure results in the entire linac being replaced or returned to a manufacturing location for reprocessing.

[0005] RF chokes are reusable RF joints that are designed to suppress the passage of high frequency RF waves while allowing the passage of low frequency RF waves. RF chokes have a high inductance for such high frequency RF waves. Conventional RF chokes contain O-ring seals. Such O-ring seals typically include a rubber O-ring in a groove on one or both of the two faces that meet to form the joint. The use of O-ring seals enables the pressurization of waveguides. The use of such RF chokes in UHV regions is not possible because the O-ring seals cause arcing when the voltage standing wave ratio (VSWR), which is a measure of the reflectivity of the waves traveling through the waveguide, swings large (i.e., changes significantly). Such arcing is due to surface currents and small leakage rates through the O-ring seals.

[0006] CF joints (originally known as ConFlat joints, although the terms CF flange and CF joint are known in the art today) are UHV compatible reusable joints. CF joints have a hex-free design in which the two flanges that form the joint are identical. CF joints include a gasket held in place between two knife edges to provide a UHV seal. Such CF joints can be baked to 500°C. However, such CF joints cannot be used in vacuum systems where there are large potential frequency and VSWR variations because under these conditions the joints can be damaged or destroyed due to resonant RF frequency nodes and / or due to large surface currents forming at the joints. Instead, CF joints can be located on pump flanges that include circular vacuum tubes that do not contain RF power. While there are RF power variants of CF flanges, they can only be placed in systems that ensure zero field for the above reasons. While it would be desirable for the location of the CF joints to coincide with the location of the zero field under normal operation, such CF joints can still be damaged in the case of high power instability.

[0007] Some known designs use a choke mode cavity, i.e., a brazed cavity that relies on a choke mode, to attenuate harmful high order modes (HOMs) and low order modes (LOMs) that can cause beam breakup in large accelerators. These choke mode cavities are designed for damping purposes and typically contain a damping dielectric material to remove unwanted trapped wave modes in the choke region. These trapped wave modes are RF modes that are localized within a region of the RF geometry without propagating from that region and that can cause damage to the RF system by causing RF breakdown or beam breakup (BBU). A drawback of typical choke mode cavities is that the Q factor (quality factor) and stored energy are much lower than in other accelerator cavity variants, resulting in the need for longer accelerator structures to achieve a given acceleration of charged particles.

[0008] It would be advantageous to use existing cavity structures to prevent damage to a linac. It would also be advantageous to provide a linac that is more adaptable. Thus, there is a need for a more versatile linac and linac joint.

[0009] The present disclosure attempts to address these and other drawbacks encountered in the prior art. SUMMARY

[0010] The present disclosure is set forth in independent claims.

[0011] According to one aspect, a reusable joint for a medical linac is provided, the reusable joint comprising a CF choke flange, a CF cover flange, and a gasket. The CF choke flange comprises a first waveguide slot, a choke slot, and a first CF slot comprising a first knife edge, wherein the choke slot is disposed radially inward from the first CF slot on the CF choke flange. The CF cover flange comprises a second waveguide slot aligned with the first waveguide slot, and a second CF slot comprising a second knife edge and aligned with the first CF slot. The gasket is disposed between and in contact with the first and second CF slots.

[0012] According to another aspect, a reusable CF choke flange for a medical linac is provided, the reusable CF choke flange comprising a first waveguide slot, a choke slot, and a first CF slot comprising a first knife edge, wherein the choke slot is disposed radially inward from the first CF slot on the reusable CF choke flange.

[0013] According to another aspect, a linac is provided, the linac comprising a first linac component, a second linac component, and the above-described reusable joint forming a non-permanent connection between the first and second linac components.

[0014] According to another aspect, a method for forming a reusable joint for a medical linac is provided, the method comprising providing a CF choke flange comprising a first waveguide slot, a choke slot, and a first CF slot comprising a first knife edge, wherein the choke slot is disposed radially inward from the first CF slot on the CF choke flange, providing a CF cover flange comprising a second waveguide slot aligned with the first waveguide slot, and a second CF slot comprising a second knife edge and aligned with the first CF slot, disposing a gasket between and in contact with the first and second CF slots, and holding the CF choke flange and the CF cover flange in abutment using an attachment device. BRIEF DESCRIPTION OF DRAWINGS

[0015] Specific embodiments will now be described by way of example only with reference to the accompanying drawings, in which:

[0016] Figure 1 A radiotherapy apparatus or device according to this disclosure is described;

[0017] Figure 2 A waveguide according to this disclosure is depicted;

[0018] Figure 3a The longitudinal sections of the choke flange and the cover flange are depicted;

[0019] Figure 3b The transverse section of the choke flange that abuts against the cover flange is depicted;

[0020] Figure 4 The cross-section of the CF connector is depicted;

[0021] Figure 5 A transverse cross-section of the CF choke according to this disclosure is depicted;

[0022] Figure 6a A perspective view of a CF choke connector according to this disclosure is depicted;

[0023] Figure 6b A transverse cross-section of the CF choke according to this disclosure is depicted;

[0024] Figure 6c A simulated broadband response of the CF choke connector according to this disclosure is depicted;

[0025] Figure 7a A perspective view of an alternative CF choke connector according to this disclosure is depicted;

[0026] Figure 7b A transverse cross section of an alternative CF choke according to this disclosure is depicted;

[0027] Figure 7c A simulation depicting the electric field present in the CF choke according to this disclosure is presented;

[0028] Figure 7d A simulation of the magnetic field present in the CF choke according to this disclosure is depicted;

[0029] Figure 8a A perspective view of an alternative CF choke connector according to this disclosure is shown;

[0030] Figure 8b A transverse cross section of an alternative CF choke according to this disclosure is depicted;

[0031] Figure 8c A simulated broadband response of an alternative CF choke according to this disclosure is depicted;

[0032] Figure 9a A perspective view of an alternative CF choke connector according to this disclosure is depicted;

[0033] Figure 9b A transverse cross section of an alternative CF choke according to this disclosure is depicted;

[0034] Figure 10 A UHV RF system according to this disclosure is described;

[0035] Figure 11a A medical linear accelerator according to this disclosure is described;

[0036] Figure 11b An enlarged view of the electron gun interface according to this disclosure is depicted.

[0037] Figure 11c An enlarged view of a linear accelerator unit according to this disclosure is depicted. Detailed Implementation

[0038] This disclosure provides a reusable connector comprising a CF choke flange, a CF cover flange, and a washer. The CF choke flange includes a CF groove disposed radially outward from the choke groove. Moving the CF groove to a larger radius and providing the choke groove at a smaller radius protects the CF groove and washer from damage by traveling RF waves. This ensures that the CF groove and washer are positioned in low electric and magnetic fields, thus preventing breakdown. This enables the use of the reusable connector in UHV regions and even in locations where high power instability might occur due to the shielding of the CF groove and washer. The advantage of the reusable connector is that it eliminates the need for brazing or welding, instead using a combined CF connector and choke connector with attachment devices (e.g., nuts and bolts) and / or clamps. This simplifies the fabrication of linear accelerator connectors, providing more efficient manufacturing and / or repair of linear accelerators. Furthermore, these features allow for the reuse of components to modify the connector and / or form one or more other connectors, providing a more versatile connector.

[0039] Figure 1 A radiotherapy apparatus is depicted, adapted to deliver and configured to deliver a beam of radiation to a patient during radiotherapy. To provide useful accompanying information for this disclosure, the apparatus and its constituent parts will be described in general. Figure 1 The apparatus described herein is in accordance with this disclosure and is suitable for use with the disclosed systems and devices. Although Figure 1 The device described is an MR linear accelerator, but embodiments of this disclosure can be any radiotherapy device, such as a linear accelerator device.

[0040] Figure 1The depicted device 100 is an MR linear accelerator. Device 100 includes an MR imaging unit 112 and a radiotherapy (RT) unit, which may include the linear accelerator unit. The MR imaging unit 112 is shown in cross-section in the figure. In operation, the MR scanner produces MR images of the patient, and the linear accelerator unit generates and shapes a radiation beam, directing the beam to a target area within the patient's body according to the radiotherapy treatment plan. The depicted device does not have the typical "casing" that typically covers MR imaging units 112 and RT units found in commercial environments (e.g., hospitals).

[0041] Figure 1 The illustrated MR linear accelerator device includes a radio frequency source 102, a waveguide 104, an electron source 106, a radiation source 106, a collimator 108 (e.g., a multi-leaf collimator configured to collimate and shape the beam), an MR imaging device 112, and a patient support surface 114. In use, the device also includes a housing (not shown) that defines an aperture together with a ring gantry. The movable support surface 114 can be used to move a patient or other object into the aperture when an MR scan and / or when radiotherapy begins. The MR imaging device 112, the RT device, and the object support surface actuator are communicatively coupled to a controller or processor. The controller may also be communicatively coupled to a memory device including computer-executable instructions executable by the controller.

[0042] RT equipment includes a radiation source and a radiation detector (not shown). Typically, the radiation detector is positioned radially relative to the radiation source. The radiation detector is adapted and configured to generate radiation intensity data. Specifically, the radiation detector is positioned and configured to detect the intensity of radiation that has passed through an object. The radiation detector can also be described as a radiation detection device and can be part of an entrance imaging system.

[0043] The radiation source may include a beam generation system. For a linear accelerator, the beam generation system may include an RF energy source 102, an electron gun 106, and a waveguide 104. The radiation source is attached to a rotatable gantry 116 so as to rotate together with the gantry 116. In this way, the radiation source can rotate around the patient, thereby allowing the therapeutic beam 110 to be applied around the gantry 116 from different angles. In a preferred embodiment, the gantry is continuously rotatable. In other words, the gantry can rotate 360 ​​degrees around the patient, and in fact, can continue to rotate beyond 360 degrees. The gantry may be annular. In other words, the gantry may be a toroidal gantry.

[0044] A radio frequency (RF) source 102 (e.g., a magnetron) is configured to generate RF waves. The RF source 102 is coupled to waveguide 104 via a circulator 118 and is configured to pulse the RF waves into waveguide 104. The RF waves can travel from the RF source 102 through an RF input window and into an RF input connector or conduit. An electron source 106 (e.g., an electron gun) is also coupled to waveguide 104 and is configured to inject electrons into waveguide 104. In the electron gun 106, electrons are thermionicly emitted from the cathode filament as it is heated. The temperature of the filament controls the number of injected electrons. The injection of electrons into waveguide 104 is synchronized with the pumping of RF waves into waveguide 104. The design and operation of the RF source 102, the electron source, and the waveguide 104 are such that the RF waves accelerate the electrons to very high energies as they propagate through waveguide 104.

[0045] The design of waveguide 104 depends on whether the linear accelerator uses standing waves or traveling waves to accelerate electrons, although waveguides typically comprise a series of cells or cavities, each connected by apertures or "iris" through which the electron beam can pass. The cavities are coupled to generate a suitable electric field mode that accelerates electrons propagating through waveguide 104. As electrons are accelerated in waveguide 104, the electron beam path is controlled by manipulating magnets or manipulating coils appropriately arranged around waveguide 104. The arranged manipulating magnets may include, for example, two sets of quadrupole magnets.

[0046] Once the electrons are accelerated, they can pass through a flight tube. The flight tube is connected to the waveguide via a connecting tube, which may be referred to as a drift tube. The electrons travel toward a heavy metal target, which may include, for example, tungsten. As the electrons travel through the flight tube, focusing magnets are arranged to guide and focus the beam onto the target.

[0047] To ensure that electron propagation is not impeded as the electron beam travels toward the target, a vacuum system, including a vacuum pump or vacuum pumping device, is used to evacuate waveguide 104. The pumping system is capable of generating ultra-high vacuum (UHV) conditions in waveguide 104 and the flight tube. The vacuum system also ensures UHV conditions in the electron gun. Electrons can be accelerated to near the speed of light in the evacuated waveguide 104.

[0048] A radiation source is configured to direct a therapeutic radiation beam 110 toward a patient located on a patient support surface 114. The radiation source may include a heavy metal target, with high-energy electrons exiting a waveguide directed toward the heavy metal target. When the electrons strike the target, X-rays are generated in various directions. A primary collimator may block X-rays traveling in certain directions and allow only forward-traveling X-rays to pass through to generate the therapeutic beam 110. The X-rays may be filtered and may pass through one or more ionization chambers for dose measurement. Before the beam enters the patient as part of radiotherapy, it may be shaped in various ways by a beam-shaping device, such as by using a multi-leaf collimator 108.

[0049] In some implementations, the radiation source is configured to emit either an X-ray beam or an electron particle beam. This implementation allows the device to provide electron beam therapy, i.e., external electron beam therapy, where electrons, rather than X-rays, are directed towards the target area. A "switch" can be made between a first mode emitting X-rays and a second mode emitting electrons by adjusting components of the linear accelerator. Essentially, the switch between the first and second modes is achieved by moving the heavy metal target into or out of the electron beam path and replacing it with a so-called "electron window." The electron window is substantially transparent to the electrons and allows them to exit the flight tube.

[0050] The object or patient support surface 114 is configured to move between a first position substantially outside the aperture and a second position substantially inside the aperture. In the first position, the patient or object can be positioned on the patient support surface. The support surface 114 and the patient can then move within the aperture to the second position so that the patient can be imaged by the MR imaging device 112 and / or imaged or treated using an RT device. The movement of the patient support surface is achieved and controlled by an object support surface actuator, which can be described as an actuation mechanism. This actuation mechanism is configured to move the object support surface in a direction parallel to and defined by the central axis of the aperture. The terms "object" and "patient" are used interchangeably herein, such that the object support surface can also be described as a patient support surface. The object support surface can also be referred to as a movable or adjustable recliner or table.

[0051] Figure 1 The depicted radiotherapy apparatus / device also includes an MR imaging device 112. The MR imaging device 112 is configured to acquire an image of an object located (i.e., positioned) on an object support surface 114. The MR imaging device 112 may also be referred to as an MR imager. The MR imaging device 112 can be a conventional MR imaging device that operates in a known manner to acquire MR data (e.g., MR images). Those skilled in the art will understand that such an MR imaging device 112 may include a primary magnet, one or more gradient coils, one or more receiving coils, and an RF pulse applicator. The operation of the MR imaging device is controlled by a controller.

[0052] The controller is a computer, processor, or other processing device. The controller may consist of several discrete processors; for example, the controller may include an MR imaging device processor that controls the MR imaging device 110; an RT device processor that controls the operation of the RT device; and an object support surface processor that controls the operation and actuation of the object support surface. The controller is communicatively coupled to memory, such as a computer-readable medium.

[0053] The linear accelerator apparatus also includes several other components and systems as those skilled in the art will understand. For example, appropriate shielding is provided to ensure that the linear accelerator does not leak radiation.

[0054] The device may be configured to perform any of the currently disclosed method steps and may contain computer-executable instructions that, when executed by a processor, cause the processor to perform any of the currently disclosed method steps. Any step configured to be performed by the device may be considered a method step of this disclosure and may be contained in computer-executable instructions executed by a processor.

[0055] In the following text, for clarity, reference will be made to radiation therapy administered to a patient. This use of the term "patient" should not be construed as limiting the application of this disclosure. This disclosure provides means for administering radiation therapy to any object. The terms "patient" and "object" are used interchangeably herein.

[0056] Figure 2 Waveguide 104 is depicted. A cross-sectional view along the longitudinal axis of waveguide 104 is shown. This waveguide 104 can be used for, for example... Figure 1 The device 100 shown can be used in other accelerators (e.g., curved accelerators such as cyclotrons or synchrotrons). The examples and discussion below relate to the acceleration of electrons, but waveguides can be used to accelerate any charged particle, and therefore can be used for any charged particle. For example, the techniques described herein can be used to accelerate protons, positrons, and ions.

[0057] A series of connected cavities, two cavities 200, are shown. Each cavity is connected along a central axis 202 via a diaphragm 204. Although a typical waveguide would have more cavities, Figure 2 Only two cavities are shown in the diagram. The exact number will vary depending on the accelerator's design specifications. Each cavity is defined by recesses within the housing made of a conductive material (typically copper).

[0058] In the following description, the term "longitudinal section" is used to define a section in a plane passing through the central axis. The term "transverse section" is used to define a section in a plane perpendicular to the central axis. The longitudinal center of an object is halfway along its longitudinal axis. For example, the longitudinal center of a cavity is a plane halfway along the central axis of that cavity.

[0059] Waveguide 104 is designed to accelerate electrons toward the target location in the longitudinal direction. To achieve this, waveguide 104 confines the RF wave in the lateral direction and transmits the RF wave along the longitudinal direction.

[0060] Each cavity 200 has a diaphragm 204 connected to the preceding cavity 200 in the sequence, and a diaphragm 204 connected to the next unit in the sequence. The diaphragms 204 and cavities 200 are centered on a central axis. In use, the central axis 202 defines an electron acceleration path along which electrons travel as they are accelerated through waveguide 104. The cavities 200 and diaphragms 204 can be axisymmetric about the central axis, forming a circular torus, i.e., a three-dimensional shape formed by scanning a two-dimensional shape around the axis. However, in other arrangements, one or more cavities 200 may not be axisymmetric about the central axis 202, which is advantageous for shifting peak field points away from the corresponding diaphragm 204.

[0061] exist Figure 2 In the waveguide shown, a "nose cone" 216 is formed at each end of the diaphragm 204, which extends the diaphragm 204 along the central axis 202 to extend into the cavity 200. However, some waveguides 104 do not include a nose cone 206.

[0062] In a typical linear accelerator, cavity 200 is fabricated by welding segments of conductive material together at a connection point. The connection point is typically located at the longitudinal center of cavity 200, i.e., at the point of maximum radius of cavity 200. Figure 2 The cavity 200 is described at point 200.

[0063] The connector described herein can connect two consecutive cavities 200 in waveguide 104, for example at the diaphragm 204 between the cavities, or it can connect two portions of cavity 200, for example at the longitudinal center of cavity 200. In general, the connector of this disclosure can also be used to connect other components of an RF system or a linear accelerator.

[0064] A model of waveguide 104 can be used to simulate the electromagnetic field introduced into waveguide 104 over time by applying a radio frequency wave. The effect of an electromagnetic field injected at one end of waveguide 104 on one or more electrons can be simulated. The acceleration of electrons along the acceleration path, the velocity of electrons at the distal end of waveguide 104 (opposite to the electron gun), and the proportion of electrons reaching the distal end of waveguide 104 when some electrons deviate laterally from the acceleration path can also be determined. In medical applications, this information can be used to determine the dose of radiation generated by waveguide 104.

[0065] When RF energy is applied to waveguide 104, an electric field is generated in waveguide 104, in the material of waveguide 104, and within cavity 200. The electric field across waveguide 104 is non-uniform. A surface electric field is formed on the surface of cavity 200. Regions with high surface electric fields are more likely to cause electrical breakdown.

[0066] Breakdown is caused by a combination of large surface electric and magnetic fields and is a complex phenomenon that depends on many factors besides the driving field. During breakdown, the number of electrons reaching the target decreases significantly. In some cases, the number of electrons reaching the target is zero.

[0067] Figure 3a and Figure 3b Choke connector 300, particularly RF choke connector, is described. Figure 3a The choke flange 302 (left-hand side) and the cover flange 314 (right-hand side) facing upwards are depicted, i.e., viewed along their longitudinal axis. Figure 3b The abutting choke flange 300 and cover flange 314 are depicted. The choke flange 302 is brought into contact with the cover flange 314 and the choke flange 302 is fixed to the cover flange 314 to form the choke connector 300. Figure 3a and Figure 3b The depicted choke flange 302 and cover flange 314 have circular cross-sections. However, it should be understood that other cross-sections, such as square and rectangular cross-sections, are also applicable.

[0068] Each of the choke flange 302 and the cover flange 314 includes a waveguide slot 304. Depending on the location of the choke 300 in the linear accelerator, in use, RF waves and / or electrons can pass along the waveguide 104 through the waveguide slot 304. Furthermore, each of the choke flange 302 and the cover flange 314 may include one or more holes 312. In use, an attachment device (not shown) can engage with the holes 312 to secure the choke flange 302 to the cover flange 314. For example, a bolt (not shown) can be inserted through each hole 312, and a nut (not shown) can be fitted to the end of the bolt. Any other suitable attachment device can be used to secure the choke flange 302 to the cover flange 314.

[0069] The choke flange 302 includes a choke groove 306 having a depth extending in the longitudinal direction. The choke groove 306 is annular, and when the choke flange 302 is engaged with the cover flange 314 to form a choke connector, the choke groove 306 forms an annular cavity. The annular groove or cavity is located at a radius greater than the radius of the waveguide slot 304. Therefore, the choke groove 306 extends around the waveguide slot 304 in the plane of the choke flange 302. For example, the depth of the choke groove 306 may extend in a direction parallel to the RF travel direction, and / or parallel to the outer edge of the choke flange 302.

[0070] The region of the cap flange 302 between the waveguide slot 304 and the choke groove 306 includes a recess 310. Due to the recess 310, when the outer edge of the surface of the choke flange 302 contacts the outer edge of the surface of the cap flange 314, the central portion of the choke flange 302 does not contact the cap flange 314. Therefore, the annular cavity formed by the choke groove 306 and the cap flange 314 is coupled to the waveguide slot 304 by means of the recess 310.

[0071] For a waveguide 104 configured to transmit an RF wave of wavelength λ, the longitudinal depth of the choke slot 306 is typically designed to be λ / 4. As those skilled in the art will understand, λ is related to the operating frequency of the transmitted wave or the RF transmission frequency. Furthermore, the lateral distance between the waveguide slot 304 and the choke slot 306 is typically designed to be λ / 4.

[0072] The choke flange 302 includes an O-ring groove 308. The O-ring groove 308 is annular and forms an annular cavity when the choke flange 302 is engaged with the cover flange 314 to form a choke connector. The annular cavity formed by the O-ring groove is located at a radius larger than both the radius of the choke groove 306 and the radius of the waveguide slot 304. The O-ring groove 308 has a depth extending in the longitudinal direction and extends in the plane of the choke flange 302 around the choke groove 306 and the waveguide slot 304. For example, the O-ring groove 308 may be formed parallel to the outer edge of the choke flange 302 and / or parallel to the choke groove 306. The O-ring groove is configured to receive an O-ring for sealing the choke flange 302 and the cover flange 314 when the attachment device is in operation. The O-ring may be formed of rubber or other suitable elastic or flexible materials. In some instances, the cover flange 314 may also include an O-ring groove.

[0073] In use, current flows along the inner surface of waveguide 104. Therefore, at the waveguide junction, this current must be able to pass through the junction without significant reflection or loss. In other words, when the choke flange 302 and the cover flange 314 contact, electromagnetic continuity must be provided between the choke flange 302 and the cover flange 314 so that RF waves of the desired frequency can propagate along waveguide 104. For current flowing longitudinally along waveguide slot 304, recess 310 and choke groove 306 together form a side branch to waveguide slot 104. At the junction between this side branch and waveguide slot 304, the side branch exhibits low impedance. The surface current flows along waveguide slot 304 and the recess formed by 310 and 314 during connection. Conversely, high impedance is presented at the outer edge of the side branch (i.e., the physical contact point when the choke flange 302 contacts the cover flange 314). This limits the current flowing through this point, thereby reducing the risk of arcing between the choke flange 302 and the cover flange 314. Since the depth of the choke slot 306 is typically designed to be λ / 4, it includes a quarter-wavelength resonant stub that provides high impedance where it meets the channel formed by the recess 310. Similarly, since the lateral distance between the waveguide slot 304 and the choke slot 306 is typically designed to be λ / 4, the channel formed by the recess 310 includes a quarter-wavelength converter that transforms the high impedance at the junction with the choke slot 306 to the low impedance at the junction with the waveguide slot 304.

[0074] Figure 4 A cross-section of a CF connector 400 is depicted. The CF connector 400 includes first and second flanges 402 and a washer 404. The washer 404 is disposed in the gap between the first and second flanges 402, i.e., in a groove or cavity. The inner side of the washer 404 ( Figure 4 The left side of the first flange 402 is a vacuum 406 (e.g., the interior portion of waveguide 104). The first and second flanges can be contacted and pressed together by bolts 410 and nuts 412. Other attachment or forcing devices can be used to press the first and second flanges 402 together. Each of the first and second flanges 402 includes a cutting edge 408 projecting into the gap between the first and second flanges 402. Each cutting edge 408 can be described as a protrusion, such as a triangular protrusion, or a ridge.

[0075] In use, by fastening the nut 412 to the bolt 410, or by other forcing means, the cutting edge 408 protrudes into the washer 404. The flange 402, or at least the cutting edge 408, is formed of a material harder than the washer 404 (which may be formed of copper), such as stainless steel or surface-hardened aluminum. The cutting edge 408 deforms the washer 404, causing it to compress and fill the gap formed in the surface of the gap between the flanges 402, thereby forming a seal between the flanges 402.

[0076] Figure 3a and Figure 3b The RF chokes shown cannot be used in UHV regions because they use O-ring seals and tend to generate arcing when the VSWR swings significantly. Figure 4 The CF connector shown is susceptible to damage (e.g., burnout) when RF waves pass along the waveguide. Therefore, a connector that addresses these issues is needed.

[0077] Figure 5 A cross-section of a CF choke connector 500 according to the present disclosure is shown. The CF choke connector 500 includes a CF choke flange 502 and a CF cover flange 514. The CF choke flange 502 and the CF cover flange 514 each include a waveguide slot 504 and may each include a hole 512 adapted to receive an attachment device (not shown). The CF choke flange includes a choke groove 506 and a recess 510. The waveguide slot 504, hole 512, attachment device, choke groove 506, and / or recess 510 may correspond to or be similar to the following regarding... Figure 3a and Figure 3b The content described herein. As used herein, a reference to a waveguide slot can be considered as a reference to any component configured to allow particle beams and / or radiation to pass through it. As used herein, a reference to a waveguide slot can be considered as a reference to RF transitions.

[0078] The CF choke flange 502 includes a first CF groove 516. The CF cover flange 514 includes a second CF groove 518. Each of the first CF groove 516 and the second CF groove 518 includes a cutting edge 522. A washer 520 is disposed between the first CF groove 516 and the second CF groove 518.

[0079] When the CF choke flange 502 and the CF cover flange 514 abut, the waveguide slot 504 of the CF choke flange 502 can be aligned with the waveguide slot 504 of the CF cover flange 514. When the CF choke flange 502 and the CF cover flange 514 abut, the first CF groove 516 can be aligned with the second CF groove 518. When the CF choke flange 502 and the CF cover flange 514 abut, the cutting edge 522 of the CF choke flange 502 can be aligned with the cutting edge 522 of the CF cover flange 514. When the CF choke flange 502 and the CF cover flange 514 abut, the hole 512 of the CF choke flange 502 can be aligned with the hole 512 of the CF cover flange 514.

[0080] A hole 512 may be configured to pass longitudinally through each of the CF choke flange 502 and the CF cover flange 514. In some examples, the inner wall of the hole 512 may be threaded to accommodate a bolt with corresponding threads. In other examples, the inner wall of the hole may be smooth or flat longitudinally. An attachment or forcing device may be disposed in the hole 512. For example, the attachment or forcing device may include a bolt and a nut. When the nut is tightened onto a bolt disposed through one or more holes 512, a cutting edge 522 deforms a washer 520, causing the washer 520 to compress and fill a gap in the surfaces of the CF choke flange 502 and the CF cover flange 514, thereby forming a seal between the CF choke flange 502 and the CF cover flange 514. Alternatively or additionally, the attachment or forcing device may include one or more clamps. The CF choke flange 502 and the CF cover flange 514 can be held abutted and pressed together by one or more of these clamps, causing the gasket 520 to deform by the blade edge 522 in a manner similar to that described above. These attachment or forcing devices enable the gasket 520 to deform uniformly, which is beneficial for forming a reliable seal.

[0081] Figure 5 The transverse section of the CF choke 500, which has a circular longitudinal section, will be depicted. In other words, one or more of the choke groove 506, the first CF groove 516, the second CF groove 518, the blade edge 522, and the washer 520 may be circular, i.e., annular.

[0082] like Figure 5 As depicted, the radius of the choke groove 506 is larger than the radius of the waveguide slot 504 relative to the center of the CF choke flange 502. The radii of the first CF groove 516, the second CF groove 518, the washer 520, and the blade edge 522 are larger than the radius of the choke groove 506. Moving these components to a larger radius and positioning the choke groove 506 at a smaller radius protects these components from damage by traveling RF waves. This ensures that the CF connector is positioned in a low electric and low magnetic field location, thus preventing breakdown. This allows the waveguide connector to be used in UHV regions, even in locations where high power instability might occur due to the shielding of the CF connector.

[0083] The CF choke connector 500 can be used at interfaces in vacuum RF systems. For example, the CF choke connector 500 can be used in linear accelerators (e.g., medical linear accelerators) or other RF systems with high power and a potentially wide range of VSWR values. While this connector has been discussed in relation to waveguides, it can also be applied to various components of linear accelerators. This connector is suitable for medical linear accelerators, such as those used for delivery in radiotherapy. For example, it can be used at interfaces between a target section and a linear accelerator, an electron gun / particle source and a linear accelerator, an RF window and a linear accelerator, and interfaces between cavities or cavity sections within a linear accelerator. These interfaces are traditionally brazed or fused. Such brazed or fused interfaces are considered a non-repairable option for medical linear accelerators because repairs or modifications require extensive rework at the factory / manufacturing site, rather than allowing for on-site repairs.

[0084] The CF choke connector 500 can be formed without brazing or welding. Instead, the CF choke connector 500 can be formed using an attachment device by holding the CF choke flange 502 and the CF cover flange 514 in abutment. For example, the attachment device may include a bolt disposed through each hole 512. A nut may be secured to the bolt to force the CF choke flange 502 against the CF cover flange 514. The CF choke connector 500 is reusable. In other words, the CF choke flange 502 and the CF cover flange 514 can be detachably coupled to each other and can be subsequently reconnected. In other words, the CF choke flange 502 and the CF cover flange 514 can be separated, and each can be reused to form the same connector or to form one or more other connectors with other linear accelerator components. A new washer 520 can be used to reformulate the same connector or to form another connector. This disclosure also includes a method for forming a reusable connector for a medical linear accelerator according to the above-described device.

[0085] For example, the nut can be detached from the bolt, allowing the CF choke flange 502 to be separated from the CF cover flange 514. Alternatively or additionally, the CF choke flange 502 can be separated from the CF cover flange 514 by removing one or more clamps from the CF choke flange 502 and the CF cover flange 514.

[0086] The advantage of the CF choke connector 500 is that it eliminates the need for brazing or welding, instead using a combination CF connector and choke connector with attachment devices such as nuts and bolts and / or clamps. This simplifies the formation of connectors for linear accelerators, thereby providing more efficient manufacturing and / or maintenance of linear accelerators. Furthermore, these features enable the reuse of components to re-form connectors and / or one or more other connectors, resulting in more versatile connectors.

[0087] This disclosure includes a linear accelerator with a reusable connector, which allows one or more linear accelerator components to be removed, replaced, and / or repaired, for example, in the field. This has the benefit of allowing for complete in-field repair, enabling the replacement of damaged or malfunctioning components, such as targets, electron guns, or RF windows. Such a linear accelerator may be referred to as a modular linear accelerator. The linear accelerator may include medical devices, such as radiotherapy devices configured to apply radiation to a subject.

[0088] A further advantage of this disclosure is that the waveguide / linear accelerator can be reverse-engineered based on changes in required usage or available resources. For example, a greater relative dimensionality can be provided by adding additional waveguide cavities. Alternatively or additionally, increased functionality can be provided by adding energy switches, different targets, and / or different particle sources to the linear accelerator. Thus, the waveguide / linear accelerator offers increased versatility and flexibility.

[0089] A linear accelerator may include multiple components having joints therebetween. At least one of these joints may be a CF choke joint 500. In other words, at least one of these joints may be formed by connecting a CF choke flange 502 to a CF cover flange 514, as per [reference to...]. Figure 5 What is depicted.

[0090] This modular design eliminates the creep and detuning issues that can arise from using indium-sealed joints with soft indium metal.

[0091] The connector design discussed in this paper can depend on the connector's intended location within the waveguide or linear accelerator, as well as the expected power, frequency range, and possible VSWR values. Connector design can include simulations of the connector, particularly electric and magnetic fields. The connector design can be optimized for a set of input conditions such as: minimizing power reflected at the connector; eliminating notch RF modes in the region of interest; and ensuring that electric and magnetic fields are below thresholds within the CF connector region (to prevent damage from RF breakdown, surface current effects, and other field-related phenomena). For specific spatial constraints, the connector design can minimize the field across the connector. Candidate connector designs can be examined to ensure they are suitable for the desired power level, for example, using runaway conditions with multistep and / or townsend. Therefore, connectors can be designed for specific spatial and power constraints. Connectors can also be designed to accommodate fabrication or manufacturing limitations or tolerances.

[0092] The following describes specific embodiments of the CF choke connector according to this disclosure.

[0093] Figure 6a A perspective view of an embodiment of the CF choke connector is shown. Figure 6bThe transverse cross-section of the CF choke is depicted. These figures illustrate the space between and around the relevant physical components of the CF choke. Figure 6c The simulated broadband response of the CF choke is depicted under the worst-case condition of setting 1 / 4 wavelength. Setting 1 / 4 wavelength gives the worst-case scenario because the field will be at its maximum under this condition. In other words, Figure 6c The amplitude of the response, expressed in decibels, is described for the frequency sweep range. From Figure 6c As can be seen, the connector is designed to be at zero at the resonant f0 = 2.998 GHz. The response increases as the frequency shifts away from zero. However, for this particular design, it is advantageous that the power remains very low, below -60 dB, within f0 ± 10 MHz.

[0094] Figure 7a A perspective view depicting alternative embodiments of the CF choke connector is shown. Figure 7b The cross-section of the CF choke is depicted. These figures illustrate the space between and around the relevant physical components of the CF choke. Variations in the design of the CF choke depend on design constraints such as space, frequency range, and the expected VSWR range that the system can anticipate. Therefore, Figure 7a and Figure 7b The described embodiments can be designed for use with Figure 6a and Figure 6b The described embodiments represent different system applications or locations. For example... Figure 7a and Figure 7b As shown, this embodiment has relative to Figure 6a and Figure 6b Extended choke groove. Figure 6a and Figure 6b The described embodiments can be compared to Figure 7a and Figure 7b The depicted embodiments are easier to manufacture, for example, based on tolerances and machinability. However, Figure 6a and Figure 6b The overall size of the depicted embodiment will be larger than Figure 7a and Figure 7b The overall size of the depicted embodiment is much larger, therefore, for Figure 6a and Figure 6b The depicted embodiment makes it difficult to deliver the shelf gasket and blade / flange. Design choices involve a balance between practicality and availability. If there are space constraints at the intended location of the joint, then... Figure 7a and Figure 7b The embodiments are used to replace Figure 6a and Figure 6b Examples of implementations.

[0095] Figure 7c Depicting in use Figure 7aand Figure 7b Simulation of the electric field present in the CF choke. Similarly, Figure 7d Depicting in use Figure 7a and Figure 7b Simulations of the magnetic field present in a CF choke connector. These figures depict the fields present between and around the relevant physical components of the CF choke connector. Figure 7c and Figure 7d As shown, the electric and magnetic fields are minimized on the outer radial surfaces of the CF choke connector (towards the top and bottom of each figure), i.e., at the location of the CF connector. Figure 7c The high electric field at the center of the simulation is depicted along the horizontal axis. The electric field decreases from the center towards the left and right sides of the simulation. Figure 7d The low magnetic field at the center of the simulation is depicted along the horizontal axis. The magnetic field increases from the center outwards towards the left and right sides of the simulation.

[0096] Although the above embodiments have a circular geometry, the CF choke and CF choke flange are not limited to this and can take any shape suitable for a specific design application. For example, the choke and / or CF connector can be circular, square, rectangular, elliptical, or spline variants. The design of the choke and / or CF connector is constrained by the design process to meet the above requirements for minimum electric field and surface electric field on the connector, and the absence of notch modes.

[0097] Figure 8a A perspective view depicting another alternative embodiment of the CF choke connector with a rectangular geometry is shown. Figure 8b The transverse cross-section of the CF choke is depicted. These figures illustrate the space between and around the relevant physical components of the CF choke. Figure 8c The simulated broadband response of the CF choke is depicted under the worst-case condition of setting 1 / 4 wavelength. In other words, Figure 8c The amplitude of the response, expressed in decibels, is described for the frequency sweep range.

[0098] While the above embodiments relate to a CF choke connector including a single connection portion, this disclosure is not limited thereto. The CF choke connector can be extended to any number of mating portions, including double-jointed and triple-jointed portions. Such embodiments may include different mating areas and / or different flange types, in which case the different portions can be mated to each other via the CF choke connector. This would be advantageous, for example, for connecting two different or mismatched portions of an RF system (e.g., having different shapes and / or diameters).

[0099] Figure 9a A perspective view depicting another alternative embodiment of the CF choke connector is shown, in which two CF choke connectors are combined (interlaced). In other words, Figure 9aThe CF choke connector includes two choke elements and may also include two CF connectors. Figure 9b The cross-section of the CF choke is depicted. This CF choke can be used to connect / connect different flange types in RF waveguide systems. These figures depict the space between and around the relevant physical components of the CF choke.

[0100] As described above, the CF choke connectors presented herein can be applied to various parts of a UHV RF system. Non-limiting examples of feasible applications are described below.

[0101] Figure 10 An example of a UHV RF system is depicted, including connections to a high-power RF, an RF window, a device under test, and a high-power phase shifter. The depicted UHV RF system can have a large VSWR range of 1-6. CF chokes can be applied, for example, at the intersection between the high-power RF region and the UHV region.

[0102] The CF choke described herein can be applied not only to RF waveguide transmission systems (e.g., WR284 / WG10) but also to various components of linear accelerators. For example, the CF choke can be used in interfaces that are conventionally brazed and welded. As non-limiting examples, these interfaces can be between: a target section and a linear accelerator; an electron gun / particle source and a linear accelerator; an RF window and a linear accelerator; and / or a waveguide cavity or part of a waveguide cavity within a linear accelerator.

[0103] Figure 11a An example of a medical linear accelerator is depicted, including an electron gun interface, a target interface, a linear accelerator unit interface, and an RF window interface. Figure 11b An enlarged view of the electron gun interface is depicted. Figure 11c Enlarged views of linear accelerator unit interfaces are depicted. The interfaces shown in these figures are traditionally brazed or fused. However, these interfaces can be connected using the CF choke connectors described herein. This provides a modular, more versatile, and more flexible medical linear accelerator.

[0104] Although the methods disclosed herein are presented in a certain order, this should not be construed as limiting the methods to that order. One or more method steps may be omitted or rearranged. Various steps may be performed in different orders. Various steps may be performed simultaneously or substantially simultaneously. Here, references to substantially simultaneous events may refer to events that at least partially overlap in time within the measurement uncertainty and / or events that occur simultaneously.

[0105] It should be understood that the above description is intended to be illustrative and not restrictive. Many other implementations will become apparent to those skilled in the art upon reading and understanding the above description. Although this disclosure has been described with reference to specific example implementations, it will be appreciated that this disclosure is not limited to the described implementations but can be practiced with modifications and changes within the scope of the appended claims. Therefore, the specification and drawings are to be considered illustrative and not restrictive. Thus, the scope of this disclosure should be determined by reference to the appended claims and the full scope of their equivalents.

Claims

1. A reusable connector for a medical linear accelerator, the reusable connector comprising: CF choke flange, including: Choke; and The first CF groove includes a first cutting edge. The choke groove is arranged radially inward from the first CF groove on the CF choke flange; CF cover flange, including: The second CF groove includes a second cutting edge and is aligned with the first CF groove; and A gasket is disposed between the first CF groove and the second CF groove and contacts both the first CF groove and the second CF groove. The CF choke flange and the CF cover flange include waveguide slots configured to allow RF waves and / or electrons to pass through the waveguide slots.

2. The reusable connector according to claim 1, wherein, The CF choke flange and the CF cover flange are held in contact by an attachment device.

3. The reusable connector according to claim 2, wherein, Both the CF choke flange and the CF cover flange include one or more holes configured to pass through them, and the attachment device includes one or more bolts and one or more nuts, wherein the one or more bolts are configured to pass through the corresponding holes of the CF choke flange and the CF cover flange, and wherein the one or more nuts are coupled to the corresponding one or more bolts to hold the CF choke flange and the CF cover flange in abutment.

4. The reusable connector according to claim 2, wherein, The attachment device includes one or more clamps arranged to hold the CF choke flange and the CF cover flange in abutment.

5. The reusable connector according to claim 3, wherein, The CF choke flange and the CF cover flange are detachably connected so as to separate the CF choke flange and the CF cover flange by disengaging the one or more nuts from the one or more bolts.

6. The reusable connector according to claim 4, wherein, The CF choke flange and the CF cover flange are detachably coupled to separate the CF choke flange and the CF cover flange by removing the one or more clamps from the CF choke flange and the CF cover flange.

7. The reusable connector according to any one of the preceding claims, wherein, The CF choke flange and the CF cover flange are not brazed or fused together.

8. The reusable connector according to any one of claims 1 to 6, wherein, The CF choke flange and the CF cover flange have circular cross sections.

9. The reusable connector according to any one of claims 1 to 6, wherein, The CF choke flange and the CF cover flange have square or rectangular cross sections.

10. A reusable connector, each reusable connector being a reusable connector according to any one of the preceding claims, wherein, The reusable connectors are combined or interleaved to form multiple joint portions.

11. A reusable CF choke flange for use in a medical linear accelerator, said reusable CF choke flange comprising: Choke groove; and The first CF groove includes a first cutting edge. The choke groove is arranged radially inward from the first CF groove on the reusable CF choke flange. The CF choke flange includes a waveguide slot, which is configured to allow RF waves and / or electrons to pass through the waveguide slot while the CF choke flange abuts against the CF cover flange including the waveguide slot.

12. The reusable CF choke flange of claim 11, comprising one or more holes configured to pass through the reusable CF choke flange and to receive an attachment device.

13. The reusable CF choke flange according to claim 12, wherein, The one or more holes are configured to accommodate one or more bolts for connection with one or more nuts.

14. The reusable CF choke flange according to any one of claims 11 to 13, wherein, The CF choke flange has a circular cross-section.

15. The reusable CF choke flange according to any one of claims 11 to 13, wherein, The CF choke flange has a square or rectangular cross-section.

16. A reusable CF choke flange, each reusable CF choke flange being a reusable CF choke flange according to any one of claims 11 to 15, for combination or interleaving with a plurality of CF cover flanges to form a plurality of engagement portions.

17. A linear accelerator, the linear accelerator comprising: First linear accelerator component; Second linear accelerator component; and The reusable connector according to any one of claims 1 to 10 is used to form a non-permanent connection between the first linear accelerator component and the second linear accelerator component.

18. The linear accelerator according to claim 17, wherein, The first linear accelerator component and / or the second linear accelerator component are selected from the target portion, electron gun, particle source, RF window, waveguide, waveguide cavity, and a portion of the waveguide cavity.

19. A method of forming a reusable connector for a medical linear accelerator, the method comprising: A CF choke flange is provided, the CF choke flange comprising: Choke; and The first CF groove includes a first cutting edge. The choke groove is arranged radially inward from the first CF groove on the CF choke flange; A CF cover flange is provided, the CF cover flange comprising: The second CF groove includes a second cutting edge and is aligned with the first CF groove; A washer is disposed between the first CF groove and the second CF groove and in contact with both the first CF groove and the second CF groove; and The CF choke flange and the CF cover flange are held in contact using an attachment device. The CF choke flange and the CF cover flange include waveguide slots configured to allow RF waves and / or electrons to pass through the waveguide slots.

20. The method according to claim 19, wherein, The method of using an attachment device to keep the CF choke flange and the CF cover flange in contact includes: providing one or more bolts through one or more corresponding holes in the CF choke flange and the CF cover flange, and attaching one or more nuts to the corresponding one or more bolts.

21. The method according to claim 19, wherein, The method of using an attachment device to keep the CF choke flange and the CF cover flange in contact includes: clamping the CF choke flange and the CF cover flange together.

22. The method according to claim 20, wherein, The CF choke flange and the CF cover flange are detachably connected so as to separate the CF choke flange and the CF cover flange by disengaging the one or more nuts from the one or more bolts.

23. The method according to claim 21, wherein, The CF choke flange and the CF cover flange are detachably coupled to separate the CF choke flange and the CF cover flange by removing one or more clamps from the CF choke flange and the CF cover flange.

24. The method according to any one of claims 19 to 23, wherein, The CF choke flange and the CF cover flange are not brazed or fused together.

25. The method according to any one of claims 19 to 23, further comprising: The CF choke flange is separated from the CF cover flange by removing the attachment device via the reusable connector; Repair components that are connected to the CF choke flange or the CF cover flange; as well as The CF choke flange is reconnected to the CF cover flange by reapplying the attachment device via the reusable connector.

26. The method according to any one of claims 19 to 23, further comprising: The CF choke flange is separated from the CF cover flange by removing the attachment device via the reusable connector; as well as The CF choke flange is connected to the second CF cover flange using an attachment device, or the CF cover flange is connected to the second CF choke flange using an attachment device.

Images