Radiation dose rate control method and control apparatus, and accelerator and radiation apparatus

Abstract

A radiation dose rate control method, which relates to the technology of radiation, and an accelerator (100). The control method is used for an electron linear accelerator (100) comprising a microwave source, an electron gun (102) and an accelerating tube (104). The control method comprises: when an electron linear accelerator (100) outputs a beam, monitoring a first event used for indicating a change of a beam output parameter (S610), wherein the beam output parameter comprises a pulse of an electron gun (102) and a microwave power of a microwave source, and the first event is determined by means of radiation protection requirements; and in response to monitoring the first event, cutting off the pulse of the electron gun (102), and switching a first microwave power of the microwave source to a second microwave power, so that the leakage dose rate of a radiation safety boundary is less than or equal to a first preset threshold (S620), wherein the level of dark current in an accelerating tube (104) under the second microwave power is less than or equal to a second preset threshold. Further provided are a radiation dose rate control apparatus, an accelerator (100), and a radiation apparatus.

Description

Irradiation dose rate control method, control device, accelerator and irradiation device

[0001] This application claims priority to Chinese patent application No. 202311864629.6 filed on December 29, 2023, the contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to the field of irradiation technology, the field of accelerators or other fields, and more particularly, to an irradiation dose rate control method, a control device, an accelerator and an irradiation device. Background Art

[0003] The leakage dose rate, also known as the leaked irradiation dose rate, refers to the radiation intensity per unit time that leaks out of the irradiation equipment through the radiation shielding protection device. In related technologies, as the use of electron linear accelerators expands, it is necessary to briefly open the shielding device during the accelerator's beam output (or when passing through the irradiation area). Radiation protection requirements must still be met under these operating conditions.

[0004] During the implementation of the disclosed inventive concept, the inventors discovered that when the shield is opened or the time spent passing through the irradiation zone lasts for a period of time (e.g., longer than one second), the electron gun high-voltage pulse is cut off during this period, while the microwave pulse is retained to control the leakage dose rate within the irradiation safety margin. In this case, the strong electric field created by the microwave pulse has a chance of pulling out a trace amount of free electrons from the surface of the accelerator tube cavity (referred to as dark current). After acceleration, these electrons collide with the target and generate X-rays, resulting in a leakage dose rate that exceeds the standard and fails to meet the radiation protection requirements. Summary of the Invention

[0005] The present disclosure provides an irradiation dose rate control method, a control device, an accelerator, and an irradiation device.

[0006] One aspect of an embodiment of the present disclosure provides an irradiation dose rate control method for an electron linear accelerator comprising a microwave source, an electron gun, and an accelerating tube, the method comprising: when the electron linear accelerator emits a beam, monitoring a first event for indicating a change in beam emission parameters, wherein the beam emission parameters include a pulse of the electron gun and a microwave power of the microwave source, and the first event is determined by irradiation protection requirements; in response to detecting the first event, cutting off the pulse of the electron gun and switching the first microwave power of the microwave source to a second microwave power, so that the leakage dose rate of the irradiation safety margin is less than or equal to a first preset threshold; wherein, at the second microwave power, the dark current level in the accelerating tube is less than or equal to a second preset threshold.

[0007] According to an embodiment of the present disclosure, the accelerating tube has a first operating frequency when emitting a beam, and has a second operating frequency after the microwave source switches to a second microwave power, and the beam-emitting parameters also include the microwave frequency of the microwave source. In response to detecting the first event, the method further includes: locking the microwave source from the first microwave frequency to the second microwave frequency, so that after beam emission is subsequently resumed, the error between the first adjustment time of the microwave source and the second adjustment time of the accelerating tube is less than or equal to a third preset threshold; wherein the first adjustment time includes the time for switching from the second microwave frequency back to the first microwave frequency, and the second adjustment time includes the time for recovering from the second operating frequency to the first operating frequency.

[0008] According to an embodiment of the present disclosure, after the first microwave power of the microwave source is switched to the second microwave power, the method further includes: if the electron linear accelerator is restored to beam emission, after the second microwave power is switched back to the first microwave power, the irradiation dose rate is restored to the level before beam emission is stopped within the first time period.

[0009] According to an embodiment of the present disclosure, switching the first microwave power of the microwave source to the second microwave power includes: switching the first pulse voltage amplitude acting on the microwave source to the second pulse voltage amplitude; wherein, under the action of the first pulse voltage amplitude, the microwave source has the first microwave power, and under the action of the second pulse voltage amplitude, the microwave source has the second microwave power.

[0010] According to an embodiment of the present disclosure, before switching the first pulse voltage amplitude acting on the microwave source to the second pulse voltage amplitude, the method further includes: determining a first correspondence between the dark current of the accelerating tube and the microwave power of the microwave source; determining a second correspondence between the microwave power difference of the microwave source and the irradiation dose rate recovery time, wherein the microwave power difference includes the difference between the first microwave power and the second microwave power, and the irradiation dose rate recovery time includes the time for returning to the level before stopping beam emission; and determining the second microwave power and the second pulse voltage amplitude based on the first correspondence and the second correspondence.

[0011] According to an embodiment of the present disclosure, at least two pulse voltage amplitudes adapted to different accelerating tubes are pre-stored, and switching the first pulse voltage amplitude acting on the microwave source to the second pulse voltage amplitude includes: determining the first pulse voltage amplitude and the second pulse voltage amplitude adapted to the accelerating tube from the at least two pulse voltage amplitudes; and switching the first pulse voltage amplitude acting on the microwave source to the second pulse voltage amplitude within a second time period.

[0012] According to an embodiment of the present disclosure, before locking the microwave source from the first microwave frequency to the second microwave frequency, the method further includes: determining the second adjustment time of the accelerating tube; determining the first adjustment time of the microwave source based on the second adjustment time and the third preset threshold; and determining the second microwave frequency based on the first adjustment time.

[0013] According to an embodiment of the present disclosure, the electron linear accelerator further includes a shielding device, and the accelerating tube is placed in the shielding device to emit beams; wherein monitoring the first event for indicating a reduction in the irradiation dose rate includes: monitoring an event in which the shielding device is opened.

[0014] According to an embodiment of the present disclosure, the shielding device includes a shielding body and a shielding plug, and a side wall of the shielding body has an opening. When the shielding device is closed, the shielding plug is plugged into the opening, and the irradiated object enters and exits the shielding device through the opening; wherein, monitoring the event of the shielding device being opened includes: monitoring the event of the shielding plug being pulled out of the opening.

[0015] According to an embodiment of the present disclosure, after cutting off the pulse of the electron gun, the method further includes: monitoring a second event for indicating the restoration of the beam emission parameters, the second event being triggered in response to the elimination of the first event; in response to monitoring the second event, restoring the pulse of the electron gun, and switching the second microwave power of the microwave source to the first microwave power, so that the electron linear accelerator resumes beam emission.

[0016] According to an embodiment of the present disclosure, the electron linear accelerator further includes an automatic frequency control system, which is used to lock the microwave source from a first microwave frequency to a second microwave frequency; in response to monitoring the second event, the method further includes: enabling the automatic frequency control system to switch the microwave source from the second microwave frequency back to the first microwave frequency to follow the first operating frequency of the accelerating tube.

[0017] Another aspect of an embodiment of the present disclosure provides an irradiation dose rate control device for an electron linear accelerator including a microwave source, an electron gun, and an accelerating tube, the device comprising: a monitoring module for monitoring a first event for indicating a change in beam emission parameters when the electron linear accelerator emits a beam, wherein the beam emission parameters include a pulse of the electron gun and a microwave power of the microwave source, and the first event is determined by irradiation protection requirements; a control system, communicatively connected to the monitoring module, for, in response to detecting the first event, cutting off the pulse of the electron gun and switching the first microwave power of the microwave source to a second microwave power, so that the leakage dose rate of the irradiation safety margin is less than or equal to a first preset threshold; wherein, at the second microwave power, the dark current level in the accelerating tube is less than or equal to the second preset threshold.

[0018] According to an embodiment of the present disclosure, the accelerating tube has a first operating frequency when emitting a beam, and has a second operating frequency after the microwave source switches to a second microwave power, and the beam-emitting parameters also include the microwave frequency of the microwave source. The device further includes: an automatic frequency control system, communicatively connected to the control system, for receiving a signal sent by the control system in response to detecting the first event, and locking the microwave source from the first microwave frequency to the second microwave frequency, so that after beam emission is subsequently resumed, the error between the first adjustment time of the microwave source and the second adjustment time of the accelerating tube is less than or equal to a third preset threshold. The first adjustment time includes the time for switching from the second microwave frequency back to the first microwave frequency, and the second adjustment time includes the time for recovering from the second operating frequency to the first operating frequency.

[0019] Another aspect of the embodiments of the present disclosure provides an electron linear accelerator, comprising: an accelerating tube; an electron gun for generating an electron beam that enters the accelerating tube; a microwave source for generating microwaves that enter the accelerating tube to accelerate the electron beam; a target for converting the accelerated electron beam into a ray beam; and an irradiation dose rate control device as described in any of the above items.

[0020] Another aspect of an embodiment of the present disclosure provides an irradiation device, comprising the electron linear accelerator as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above contents and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0022] FIG1 exemplarily shows a system block diagram of an electron linear accelerator according to an embodiment of the present disclosure;

[0023] FIG2 schematically shows a simplified structural diagram of an electron linear accelerator when emitting a beam according to an embodiment of the present disclosure;

[0024] FIG3 schematically shows a simplified structural diagram of the stage of replacing the sample to be tested according to an embodiment of the present disclosure;

[0025] FIG4 schematically shows a schematic diagram of a leakage dose level and a radiation output dose rate under an ideal state according to an embodiment of the present disclosure;

[0026] FIG5 schematically shows a schematic diagram of a leakage dose level and a radiation output dose rate in an actual state according to an embodiment of the present disclosure;

[0027] FIG6 schematically shows a flow chart of an irradiation dose rate control method according to an embodiment of the present disclosure;

[0028] FIG7 schematically shows a flow chart for determining the second microwave power and the second pulse voltage amplitude according to an embodiment of the present disclosure;

[0029] FIG8 schematically shows a flow chart of switching pulse voltage amplitude according to an embodiment of the present disclosure;

[0030] FIG9 schematically shows a “frequency difference-dose rate” relationship diagram according to an embodiment of the present disclosure;

[0031] FIG10 schematically shows a flow chart for determining a second microwave frequency according to an embodiment of the present disclosure;

[0032] FIG11 schematically shows a flow chart of beam recovery according to an embodiment of the present disclosure;

[0033] FIG12 schematically shows a block diagram of a microwave circuit control of an electron linear accelerator according to another embodiment of the present disclosure;

[0034] FIG13 schematically shows a block diagram of an electronic device suitable for implementing the irradiation dose rate control method according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0035] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0036] To facilitate a better understanding of the technical solution, the following definitions are given of the terms used in some embodiments of the present disclosure:

[0037] The radiation dose rate refers to the radiation dose per unit time.

[0038] The leakage dose rate refers to the radiation intensity that leaks to the outside through the radiation shielding device per unit time.

[0039] Dark current refers to the current generated in the accelerating tube when there is no electron beam entering the accelerating tube from the electron gun.

[0040] The first microwave power refers to the microwave power of the microwave source when the electron linear accelerator emits a beam.

[0041] The second microwave power refers to the microwave power of the microwave source after the electron linear accelerator stops emitting beams (cuts off the pulses of the electron gun). The second microwave power may be different between different accelerating tubes.

[0042] The first operating frequency refers to the operating frequency of the accelerating tube when the electron linear accelerator emits a beam.

[0043] The second operating frequency refers to the operating frequency of the accelerating tube after the electron linear accelerator stops emitting beams (cuts off the pulses of the electron gun).

[0044] The first microwave frequency refers to the microwave frequency fed into the accelerating tube by the microwave source controlled by the automatic frequency control system to follow the operating frequency of the accelerating tube when the electron linear accelerator emits a beam.

[0045] The second microwave frequency refers to the frequency that the automatic frequency control system locks the microwave source to a fixed value after the electron linear accelerator stops emitting beams (cuts off the pulses of the electron gun) and feeds into the accelerating tube. The second microwave frequency may vary between different accelerating tubes.

[0046] In related technologies, the classic use of an electron linear accelerator is to generate two continuous, stable high-voltage pulses upon receiving a beam-delivery command. One pulse acts on a microwave source (klystron or magnetron) to generate microwaves, while the other acts on an electron gun to generate an electron beam. The former accelerates the electron beam within the accelerator tube and then strikes a target, producing X-rays. The accelerator is placed within a shielding device (or self-shielding device). The leakage dose level at the shielding device's outer boundary (or safety distance boundary) should meet radiation protection requirements when the accelerator is delivering its maximum dose.

[0047] With the expansion of accelerator usage scenarios, it is necessary to open the shielding device for a short time during the accelerator beam output (or passing through the irradiation area). Under such conditions, radiation protection requirements must still be met. The current methods are divided into the following according to the actual working conditions:

[0048] 1. When the shield is opened or the time spent in the irradiation zone is less than 1 second, the electron gun high-voltage pulse and the microwave source high-voltage pulse are simultaneously cut off. During this period, the leakage dose rate level is at the natural background level. Because the beam interval is short, the accelerator output radiation dose rate can almost immediately return to normal levels when the two high-voltage pulses are restored.

[0049] 2. When the shield is opened or the time spent passing through the irradiation zone lasts for several seconds, the electron gun high-voltage pulse is cut off, the microwave source pulse is retained, and the trigger frequency is reduced. In this case, the leakage dose level of some accelerators may exceed the standard, or the output dose rate recovery speed may be slower than expected. This does not meet the requirements of applications that require dose rate stability or are sensitive to cumulative dose.

[0050] Although the accelerator's shielding shuts off the high-voltage pulses from the electron gun when it's open, the strong electric field created by the microwave pulses has a chance of pulling out a tiny amount of free electrons from the surface of the accelerator tube's cavity (known as dark current), accelerating them and striking the target to generate X-rays (leakage dose). In a certain amount of production practice, it was discovered that different accelerator tubes of the same type have different dark current microwave thresholds. As a result, while achieving the same performance targets, some accelerators' leakage dose levels meet the requirements, while others exceed them. This introduces uncertainty into the overall radiation protection design, and even necessitates the addition of radiation protection hardware near the end of the project, which is quite unfortunate.

[0051] Some embodiments of the present disclosure provide an irradiation dose rate control method that can monitor a first event indicating a change in beam parameters during beam emission from an electron linear accelerator. In response to the detection of the first event, the electron gun pulse is cut off and the microwave source's first microwave power is switched to a second microwave power. This method effectively controls the dark current level within the accelerating tube, preventing the generation of dark current that, after acceleration, impacts the target and generates X-rays. This method ensures that the leakage dose rate within the irradiation safety margin is less than or equal to a first preset threshold, avoiding excessive leakage dose rates and meeting radiation protection requirements.

[0052] In some other embodiments of the present disclosure, the irradiation dose rate control method can further, in response to detecting a first event, lock the microwave source from the first microwave frequency to a second microwave frequency, such that after beam emission is subsequently restored, the error between the first adjustment time of the microwave source and the second adjustment time of the accelerating tube is less than or equal to a third preset threshold. This improves the efficiency of the microwave source's microwave frequency tracking the accelerating tube's operating frequency, and by locking the microwave source to the second microwave frequency, after beam emission is subsequently restored, the microwave source's first adjustment time is as close as possible to the accelerating tube's operating frequency change time, thereby reducing the irradiation dose rate recovery time.

[0053] In other embodiments of the present disclosure, the irradiation dose rate control method, when the electron linear accelerator beam is restored and the second microwave power is switched back to the first microwave power, restores the irradiation dose rate to the level before beam emission ceased within a first time period. This method provides a method for switching the microwave power to an appropriate value to balance dark current magnitude and dose rate stability. The operation of switching the microwave source from the first microwave power to the second microwave power not only controls the dark current level within the accelerating tube but also takes into account the recovery time of the irradiation dose rate, achieving the technical effect of switching the second microwave power to an appropriate level to balance dark current magnitude and dose rate stability.

[0054] Other embodiments of the present disclosure further provide an irradiation dose rate control device, an electron accelerator, and an irradiation device applying the irradiation dose rate control method.

[0055] The following describes in detail an exemplary application scenario or structural block diagram of the present disclosure in conjunction with the accompanying drawings, and also illustrates, by way of example, problems existing in related technologies and embodiments of technical solutions for solving the problems under the overall inventive concept of the present disclosure in conjunction with the application scenario or structural block diagram.

[0056] 1 exemplarily shows a system block diagram of an electron linear accelerator according to some embodiments of the present disclosure. The accelerator 100 may include: an electron gun 102, an accelerating tube 104, a target 106, a shielding device 110, a detector 112, and a microwave system 114 including a microwave source.

[0057] The electron gun 102 is used to generate an electron beam to enter the accelerating tube 104. In the present disclosure, the electron gun 102 can be, for example, a conventional diode gun or a grid-controlled gun power supply.

[0058] The accelerating tube 104 is used to accelerate the electron beam emitted by the electron gun 102 to a predetermined energy. The accelerating tube 104 has an electron input port and a microwave feed port. The electron input port is coupled to the output of the electron gun 102 to receive the electron beam. The microwave feed port is coupled to the output of the microwave source to feed microwaves generated by the microwave source into the accelerating tube 104. For example, the predetermined energy of the accelerated electron beam is 8.5 MeV to 14 MeV (for example only). The energy of the electron beam accelerated by the accelerating tube 104 is continuously adjustable.

[0059] Target 106 is used to receive electron beam bombardment, generating radioactive radiation. The radioactive radiation generated by target 106 includes X-rays. Target 106 can, for example, utilize a gold-copper composite target structure, capable of generating a high dose of X-rays. The target can be water-cooled. By modifying the target structure to achieve three-way water cooling, the target area can be adequately cooled, preventing damage to the target structure due to excessive temperatures.

[0060] The shielding device 110 is used to shield radioactive rays, and for example includes one or more shielding layers, wherein the shielding layer is made of at least lead and tungsten.

[0061] The detector 112 is used to receive radioactive rays and generate radiation data for subsequent analysis.

[0062] Microwave system 114 is used to provide a microwave electromagnetic field to accelerator tube 104, accelerating the electron beam to a predetermined energy. As a fundamental component of the electron linear accelerator, microwave system 114 includes a microwave source and a microwave transmission system. The microwave source generates microwaves of varying frequencies in response to voltage pulses. A klystron or magnetron can be used as the microwave source.

[0063] The accelerator 100 further includes a control system (not shown in FIG. 1 ), coupled to the microwave source and the electron gun, for controlling the microwave source to generate microwaves of different frequencies, thereby switching the accelerating tube 104 between different resonance modes to generate electron beams of corresponding energies.

[0064] In some embodiments, the irradiation device provided by the present disclosure may include a device having an accelerator 100 for mineral composition analysis, and the device may include three accommodating spaces distributed in parallel. Preferably, the detector 112 is located in the first accommodating space. The target 106, the electron gun 102, the accelerating tube 104 and the shielding device 110 are located in the second accommodating space. The microwave system 114 is located in the third accommodating space. It can be understood that the irradiation device can also be provided with other shielding structures in addition to the shielding device 110, and the present disclosure does not limit it. The irradiation dose rate control method of the embodiment of the present disclosure can be used in the stage of the sample to be tested before replacing the target 106, such as opening the shielding device, placing the sample to be tested in front of the target 106, and closing the shielding device.

[0065] In other embodiments, the irradiation device provided by the present disclosure may include a security inspection device in the field of security inspection, for example, including: an inspection channel, a radiation source (such as accelerator 100). The object to be inspected is suitable for being placed in the inspection channel. The detector 112 is used to detect at least a portion of the X-ray beam after interacting with the object to be inspected. Exemplarily, the object to be inspected includes vehicles, luggage, etc., and is suitable for quickly, efficiently, and high-quality identification of items loaded on vehicles such as vans, container trucks, tank trucks, dump trucks, pickup trucks, off-road vehicles, and cars, thereby achieving the purpose of security inspection. Alternatively, it is not limited to security inspection of items loaded on the above-mentioned vehicles, and can also be used to perform radiation inspection on items in other vehicles or containers, such as luggage, logistics packages, canned or barreled items, etc. Through security inspection, it can be confirmed whether the items contain prohibited items or high-risk items such as firearms, ammunition, explosives, drugs, controlled devices, flammable and explosive items, poisons, corrosive items, radioactive items, infectious substances, precious metals, etc. The irradiation dose rate control method of the present disclosure embodiment can be used during the stage when a person passes through the irradiation area.

[0066] In particular, it should be noted that the structures and application scenarios of the above-mentioned accelerator and irradiation device do not constitute limitations on the present disclosure, and the specific structures can be modified within the scope of the inventive concept of the present disclosure.

[0067] FIG2 schematically illustrates a simplified structural diagram of an electron linear accelerator during beam emission according to an embodiment of the present disclosure. FIG3 schematically illustrates a simplified structural diagram of the stage of replacing a sample to be tested according to an embodiment of the present disclosure. FIG4 schematically illustrates a schematic diagram of leakage dose levels and radiation output dose rates under ideal conditions according to an embodiment of the present disclosure. FIG5 schematically illustrates a schematic diagram of leakage dose levels and radiation output dose rates under actual conditions according to an embodiment of the present disclosure.

[0068] 2 and 3 , the shielding device 110 can be made of shielding materials such as lead and tungsten. The shielding space defined by the shielding device 110 may include an accelerating tube holder (not shown), which secures the accelerating tube 104 and the target 106 together. The shielding device 110 has an opening near the target 106 to allow samples to enter and exit the shielding space for replacement. The sample can be placed in the radiation beam path of the target 106 for irradiation. The opening is configured to allow a tungsten plug to be inserted or removed to close or open the shielding device.

[0069] 4 and 5 , when the shielding device is closed, the microwave source high-voltage pulse and the electron gun high-voltage pulse are normally fed into the accelerator tube, and the ray output dose rate (i.e., the irradiation dose rate) is maintained in a stable state, thereby realizing irradiation scanning of the sample. When the shielding device is opened, the electron gun high-voltage pulse is switched, the microwave source is fed with a lower pulse voltage amplitude, and is switched to a lower microwave frequency. Under the ideal state shown in FIG5 , during the period when the shielding device is closed and the shielding device is opened, the actual leakage dose level (i.e., the leakage dose rate value) is below the safe leakage dose level, and after the shielding device is closed again, the ray output dose rate is rapidly increased to the normal irradiation level. For some accelerators, the actual state shown in FIG6 appears. Due to the discreteness of the accelerator vacuum device, even if the same control measures are taken, the leakage dose level of some accelerators still exceeds the standard, or the output dose rate recovery speed is slower than expected. This cannot meet the needs for applications that are sensitive to dose rate stability or cumulative dose.

[0070] The following will describe the irradiation dose rate control method provided by some embodiments of the present disclosure from Figures 6 to 11 in combination with the description of Figures 1 to 5.

[0071] FIG6 schematically shows a flow chart of an irradiation dose rate control method according to an embodiment of the present disclosure.

[0072] As shown in FIG6 , the irradiation dose rate control method of this embodiment includes:

[0073] In operation S610 , when the electron linear accelerator emits a beam, a first event for instructing to change beam emission parameters is monitored, wherein the beam emission parameters include a pulse of the electron gun and a microwave power of the microwave source, and the first event is determined by radiation protection requirements.

[0074] The beam emission of an electron linear accelerator refers to the emission of a beam of radiation. Radiation protection requirements refer to requirements formulated to ensure safety during the irradiation process. For example, the dose irradiated to the human body is limited outside the irradiation safety boundary. The irradiation safety boundary can be determined, for example, based on the distance from the irradiation device. The first preset threshold is used to control the maximum leakage dose rate of the irradiation safety boundary. The beam emission parameters refer to the parameters that control the emission of the ray beam in the electron linear accelerator, and can include the pulse amplitude of the electron gun, the pulse amplitude of the microwave source, the microwave power and microwave frequency of the microwave source, etc. The first event can be any event determined according to the radiation protection requirements.

[0075] 2 and 3 , the accelerating tube is placed in a shielding device to emit beams, wherein monitoring the first event for indicating a reduction in the irradiation dose rate includes monitoring an event in which the shielding device is opened.

[0076] In some embodiments, referring to FIG2 and FIG3 , a shielding device includes a shielding body and a shielding plug (e.g., a tungsten plug). A side wall of the shielding body has an opening. When the shielding device is closed, the shielding plug is inserted into the opening, and the irradiated object enters and exits the shielding device through the opening. Monitoring the shielding device opening event includes monitoring the shielding plug being removed from the opening.

[0077] In operation S620 , in response to detecting the first event, the pulse of the electron gun is cut off, and the first microwave power of the microwave source is switched to a second microwave power so that the leakage dose rate of the irradiation safety margin is less than or equal to a first preset threshold.

[0078] Wherein, at the second microwave power, the dark current level in the accelerating tube is less than or equal to a second preset threshold.

[0079] Exemplarily, referring to Figures 2 and 3, the peripheral safety boundary dose rate (i.e., the leakage dose rate) is less than the first preset threshold, i.e., 2.5uSv / h (for example only). The second preset threshold can be determined based on the first preset threshold. For example, when the dark current value is less than or equal to the second preset threshold, the leakage dose rate should be less than 2.5uSv / h. Therefore, it is possible to predetermine the value of the dark current that can make the leakage dose rate greater than or equal to 2.5uSv / h, thereby determining the second preset threshold (this value is the value represented in current units).

[0080] According to the embodiments of the present disclosure, the dark current level in the accelerating tube can be effectively controlled to avoid the generation of dark current that hits the target after acceleration to generate X-rays, thereby making the leakage dose rate of the irradiation safety boundary less than or equal to the first preset threshold to avoid an excessively high leakage dose rate and meet the irradiation protection requirements.

[0081] In other embodiments, after the first microwave power of the microwave source is switched to the second microwave power, if the electron linear accelerator beam emission is restored and the second microwave power is switched back to the first microwave power, the irradiation dose rate recovers to the level before the beam emission is stopped within the first time period.

[0082] For example, the first time period is within 1 to 2 microwave pulses (for example only). Therefore, the second microwave power can be predetermined according to the dark current level of the accelerating tube and the irradiation dose rate recovery time (such as the dose rate rise time shown in FIG5 ).

[0083] Specifically, the key to controlling leakage dose lies in controlling the magnitude of dark current. As shown in Figures 2-5, when the tungsten plug is open, in addition to shutting off the electron gun's high-voltage pulses, reducing dark current levels is crucial for reducing leakage dose. Experimental verification has shown a positive correlation between dark current and microwave pulse power. When microwave pulse power is reduced to a certain level, leakage dose rates close to background can be measured even in the outer safety boundary (shown in Figure 3), where leakage dose rates are weak. However, in practice, while the safety boundary dose rate meets design requirements, such as 2.5 uSv / h, microwave power should be maintained as high as possible. This is because even when no electrons need to be accelerated within the accelerator tube, microwaves are required to maintain the tube temperature and minimize deformation during both normal sample irradiation and sample replacement. This deformation corresponds to the operating frequency of the accelerator tube. Although the AFC (automatic frequency control) system tracks the operating frequency of the accelerator tube in real time and adjusts the microwave frequency fed into the accelerator tube to keep them as equal as possible, the smaller this deformation difference, the shorter the dose rate rise time shown in Figure 4, and the more likely it is to meet dose rate stability requirements. Therefore, reducing the microwave power to an appropriate level to take into account both the dark current size and the stability of the irradiation dose rate is the key to this technical solution.

[0084] According to embodiments of the present disclosure, a solution is provided for switching microwave power to an appropriate value to balance dark current magnitude and dose rate stability. Switching a microwave source from a first microwave power to a second microwave power not only controls the dark current level within the accelerating tube but also takes into account the recovery time of the irradiation dose rate, achieving the technical effect of switching the second microwave power to an appropriate level to balance dark current magnitude and irradiation dose rate stability.

[0085] In some embodiments, switching the first microwave power of the microwave source to the second microwave power includes switching a first pulse voltage amplitude applied to the microwave source to a second pulse voltage amplitude, wherein the microwave source has the first microwave power under the first pulse voltage amplitude and has the second microwave power under the second pulse voltage amplitude.

[0086] When a high-voltage pulse acts on a microwave source (such as a klystron or magnetron), the source generates microwave pulses. The microwave power of the microwave source is positively correlated with the pulse voltage amplitude: the higher the pulse voltage, the greater the microwave power. Thus, the dark current magnitude is positively correlated with the klystron high-voltage pulse amplitude.

[0087] For example, a microwave source in an electron linear accelerator can switch microwave power by adjusting the pulse voltage amplitude. Under the action of a first pulse voltage amplitude, the microwave source generates and outputs a first microwave power. When a first event is detected, the first pulse voltage amplitude is switched to a second pulse voltage amplitude as needed. Under the action of the second pulse voltage amplitude, the microwave source adjusts and outputs a second microwave power accordingly.

[0088] By switching the pulse voltage amplitude, the microwave source can flexibly adjust the microwave power level to meet the requirements for leakage dose rate and irradiation dose rate stability (such as recovery time) during irradiation. This switching can achieve control of irradiation dose rate stability and ensure that the leakage dose rate is within an acceptable range, while providing strong flexibility and adjustability.

[0089] FIG7 schematically shows a flow chart of determining the second microwave power and the second pulse voltage amplitude according to an embodiment of the present disclosure.

[0090] Before the first pulse voltage amplitude acting on the microwave source is switched to the second pulse voltage amplitude, as shown in FIG7 , this embodiment includes:

[0091] In operation S710 , a first corresponding relationship between a dark current of an accelerating tube and a microwave power of a microwave source is determined.

[0092] For example, the relationship between the dark current of the accelerating tube and microwave power can be determined in advance through experiments or simulation analysis. For example, by gradually increasing the microwave power and monitoring the changes in the dark current of the accelerating tube, a first correspondence between the dark current and microwave power can be established. This allows the dark current of the accelerating tube to be predicted based on the changes in microwave power in subsequent operations.

[0093] In operation S720, a second correspondence between a microwave power difference value and an irradiation dose rate recovery time of the microwave source is determined, wherein the microwave power difference value includes a difference between the first microwave power and the second microwave power, and the irradiation dose rate recovery time includes a time for the irradiation dose rate to recover to a level before beam emission stops after the shield is closed.

[0094] For example, to determine the second correspondence, a series of experiments or simulation analyses can be conducted in advance. By monitoring and recording the irradiation dose rate at different microwave power differences, a correspondence between the microwave power difference and the irradiation dose rate recovery time can be established. In this way, the irradiation dose rate recovery time can be predicted based on the microwave power difference.

[0095] In operation S730, a second microwave power and a second pulse voltage amplitude are determined based on the first correspondence and the second correspondence, wherein the first correspondence and the second correspondence are adapted to the performance of the accelerating tube, and the performance of different accelerating tubes may be the same or different.

[0096] Different accelerating tubes may have different structures, materials, dimensions, and operating parameters, resulting in performance differences. These differences may include, but are not limited to, acceleration efficiency, energy loss, dark current levels, and transmission efficiency. Based on the specific accelerating tube performance, the corresponding parameters and corresponding relationships are determined in advance through experiments, testing, or simulation analysis. This ensures that the first and second corresponding relationships are tailored to the accelerating tube's performance, achieving optimal microwave power regulation and irradiation dose rate control.

[0097] By using the first correspondence, the second microwave power can be determined based on the dark current of the accelerating tube. The second correspondence can be used to predict the recovery time of the irradiation dose rate. Based on this information, the second microwave power and the corresponding second pulse voltage amplitude can be determined to meet the requirements of balancing dark current magnitude and dose rate stability.

[0098] It is particularly important to note that operations S710 through S730 are performed based on the performance and specific requirements of the accelerating tube. Different accelerating tubes may have different first and second correspondences, and therefore, their second microwave power and second pulse voltage amplitude may vary. In other words, the specific performance characteristics of different accelerating tubes must be considered, and the operating parameters and correspondences must be adjusted and adapted accordingly to ensure the effectiveness and reliability of the use of different accelerating tubes.

[0099] FIG8 schematically shows a flow chart of switching pulse voltage amplitude according to an embodiment of the present disclosure.

[0100] As shown in FIG8 , at least two pulse voltage amplitudes adapted to different accelerating tubes are pre-stored, and switching the first pulse voltage amplitude acting on the microwave source to the second pulse voltage amplitude includes:

[0101] In operation S810, a first pulse voltage amplitude and a second pulse voltage amplitude adapted to an accelerating tube are determined from at least two pulse voltage amplitudes.

[0102] In operation S820, the first pulse voltage amplitude applied to the microwave source is switched to a second pulse voltage amplitude during a second time period.

[0103] For example, at least two pulse voltage amplitudes adapted to different accelerating tubes are pre-stored so that corresponding pulse voltage amplitudes can be found for different accelerating tubes, and the microwave power of the microwave source can be switched and adjusted at different stages.

[0104] According to the embodiments of the present disclosure, more than ten levels of pulse voltage amplitudes can be pre-stored, and the pulse voltage amplitude of the microwave source can be switched quickly (such as between two microwave pulses).

[0105] In some embodiments, the accelerating tube has different temperatures at the first and second microwave powers, which in turn affects the operating frequency. Therefore, the specific value of switching to the second microwave power affects the irradiation dose rate recovery time. Furthermore, the time it takes for the microwave frequency to adjust to the operating frequency during microwave power switching also affects the irradiation dose rate recovery time. The following further describes an embodiment of switching the microwave frequency to an appropriate value to enhance rapid irradiation dose rate recovery.

[0106] FIG9 schematically shows a “frequency difference-dose rate” relationship diagram according to an embodiment of the present disclosure.

[0107] Figure 9 shows the frequency difference-dose rate relationship after the tungsten plug is closed. The frequency difference Δf represents the difference in the operating frequency of the accelerating tube at different temperatures. After the shield is opened for a few seconds to "cool down" (low-frequency (several hertz), low-power microwave pulses), the operating frequency of the accelerating tube is at P1. When the shield is closed, the microwave power recovers to a high-frequency (hundreds of hertz) high-power state within one or two pulses, and the optimal operating point of the accelerating tube moves toward P0. The speed of this movement is directly proportional to the microwave power. To ensure that the X-ray dose rate is always at its maximum, the AFC system adjusts the microwave source's frequency to track the operating frequency of the accelerating tube. This adjustment process, time t1 (see Figure 9), is often greater than the time it takes for the accelerating tube's frequency to change due to temperature rise (i.e., the second adjustment time). This prolongs the X-ray dose rate recovery time, as shown in the dose rate rise time shown in Figure 5.

[0108] In some embodiments, the accelerating tube has a first operating frequency during beam emission and a second operating frequency after the microwave source switches to a second microwave power. The beam emission parameters also include the microwave frequency of the microwave source. In response to detecting a first event, the system further includes: locking the microwave source from the first microwave frequency to the second microwave frequency, such that, after beam emission is subsequently resumed, the error between the first adjustment time of the microwave source and the second adjustment time of the accelerating tube is less than or equal to a third preset threshold. The first adjustment time includes the time it takes to switch from the second microwave frequency back to the first microwave frequency, and the second adjustment time includes the time it takes to return from the second operating frequency to the first operating frequency.

[0109] According to the embodiments of the present disclosure, the first adjustment time can be effectively shortened. Specifically, referring to Figures 2 and 3, a first event that reflects the opening or closing of the tungsten plug (or passing through or leaving the irradiation zone) in real time is monitored. When the shield is opened (passing through the irradiation zone), the AFC system locks the klystron (or magnetron) to output the microwave frequency to the second microwave frequency, so that it is located at the Ps position. The selection of the Ps position can be determined through manual experiments and stored in the control system or automatically confirmed and stored by designing a self-learning program. The principle is to make the first adjustment time t2 as close as possible to the frequency change time of the accelerating tube itself, that is, the error between the first adjustment time of the microwave source and the second adjustment time of the accelerating tube is less than or equal to the third preset threshold.

[0110] FIG10 schematically shows a flow chart of determining the second microwave frequency according to an embodiment of the present disclosure.

[0111] Before locking the microwave source from the first microwave frequency to the second microwave frequency, as shown in FIG10 , this embodiment includes:

[0112] In operation S1010 , a second adjustment time of the accelerating tube is determined.

[0113] For example, based on the structure and working principle of the accelerating tube, and considering the physical processes and parameter changes inside the accelerating tube, a series of experiments or theoretical analysis and calculations can be conducted to determine the time required for the accelerating tube to recover from the second operating frequency to the first operating frequency.

[0114] In operation S1020, a first adjustment time of the microwave source is determined based on the second adjustment time and a third preset threshold.

[0115] The time required for the microwave source to switch from the second microwave frequency back to the first microwave frequency, i.e., the first adjustment time, is determined based on the accelerating tube's second adjustment time and a preset error threshold. This time is designed to ensure that the microwave source can quickly return to its original operating frequency after the frequency switch, meeting the accelerating tube's requirements and maintaining the accuracy and stability of the radiation output.

[0116] In operation S1030, a second microwave frequency is determined based on the first adjustment time.

[0117] For example, by gradually adjusting the frequency of the microwave source during an experiment and observing and recording the first adjustment time at different frequencies, a second microwave frequency that matches the first adjustment time can be found. For example, through iterative optimization, with the first microwave frequency determined, the second microwave frequency can be continuously adjusted until a frequency that matches the first adjustment time is obtained.

[0118] According to the embodiments of the present disclosure, the microwave source can be synchronized with the operating frequency of the accelerator tube as quickly as possible during the frequency switching process, so that the accelerator can return to a normal working state as quickly as possible after beam output is restored, maintaining the accuracy and stability of the radiation output to meet irradiation requirements.

[0119] In particular, operations S1010 through S1030 are performed based on the performance and specific requirements of the accelerating tube and microwave source. Different accelerating tubes may have different second adjustment times, and different klystrons may have different first adjustment times even at the same second microwave frequency. In other words, the specific conditions of different accelerating tubes and fine-tuning tubes must be considered and adjusted accordingly to ensure effectiveness and reliability.

[0120] FIG11 schematically shows a flowchart of beam recovery according to an embodiment of the present disclosure.

[0121] After the pulse of the electron gun is cut off, as shown in FIG11 , the embodiment includes:

[0122] In operation S1110 , a second event indicating restoration of beam-out parameters is monitored, where the second event is triggered in response to elimination of the first event.

[0123] For example, the first event is the opening of the tungsten plug, while the second event is the closing of the tungsten plug. After the first event is eliminated, the occurrence of the second event is detected to indicate the timing for restoring beam parameters. The triggering of the second event indicates that the accelerator has been allowed to return to normal operating conditions and irradiation operations can be carried out.

[0124] In operation S1120, in response to detecting the second event, the electron gun pulse is restored, and the second microwave power of the microwave source is switched to the first microwave power, so that the electron linear accelerator resumes beam emission. The time to resume beam emission can be calculated from the time the electron gun pulse is re-fed or the time the first event is eliminated.

[0125] After the second event is detected, the emission and acceleration of the electron beam are restarted, and the first pulse voltage amplitude is applied to the microwave source to switch back to the first microwave power, so that the electron linear accelerator can restore the normal beam emission state in time.

[0126] In some embodiments, the electron linear accelerator further includes an automatic frequency control system configured to lock the microwave source from the first microwave frequency to the second microwave frequency. In response to detecting the second event, the system further includes enabling the automatic frequency control system to switch the microwave source from the second microwave frequency back to the first microwave frequency to match the first operating frequency of the accelerating tube.

[0127] According to the embodiments of the present disclosure, the frequency of the microwave source can be monitored in real time and adjusted and controlled as needed, reducing manual intervention and operation and improving the automation level of the accelerator system. This allows the microwave source frequency to efficiently track the first operating frequency of the accelerating tube, thereby increasing the irradiation dose rate ramp-up time.

[0128] In some embodiments, referring to Figures 1 to 11, if, in response to detecting a first event, the microwave source is switched to a second microwave power to balance the dark current magnitude and irradiation dose rate stability, and locked to the second microwave frequency to approximate the time when the operating frequency of the accelerating tube changes, then the switching of microwave power and the locking of microwave frequency are intrinsically linked. Specifically, when there are no electrons in the accelerating tube that need to be accelerated, microwaves are used to maintain the temperature of the accelerating tube, and the microwave power can affect the dark current level and the tube body temperature. At the same time, there will be a deformation difference before and after switching microwave power, which corresponds to the operating frequency of the accelerating tube. In order to ensure that the time (i.e., the first adjustment time) when the AFC system adjusts the microwave source microwave frequency to follow the operating frequency of the accelerating tube is close to the time (i.e., the second adjustment time) when the accelerating tube's own frequency changes due to temperature rise, an appropriate second microwave frequency value is determined in advance to achieve this goal.

[0129] FIG12 schematically shows a block diagram of a microwave circuit control of an electron linear accelerator according to another embodiment of the present disclosure.

[0130] In some embodiments, the irradiation dose rate control device includes a monitoring module for monitoring a first event indicating a change in beam parameters during beam emission from an electron linear accelerator, wherein the beam parameters include the pulse of the electron gun and the microwave power of the microwave source, and the first event is determined by radiation protection requirements. A control system is communicatively connected to the monitoring module and is configured to, in response to detecting the first event, cut off the pulse of the electron gun and switch the first microwave power of the microwave source to a second microwave power, so that the leakage dose rate within the irradiation safety margin is less than or equal to a first preset threshold. At the second microwave power, the dark current level within the accelerating tube is less than or equal to the second preset threshold, and after beam emission is subsequently resumed, the irradiation dose rate recovers to the level before beam emission was stopped within a first time period.

[0131] In some embodiments, the accelerating tube has a first operating frequency when emitting a beam, and has a second operating frequency after the microwave source switches to a second microwave power, and the beam emission parameters also include the microwave frequency of the microwave source. The irradiation dose rate control device also includes:

[0132] An automatic frequency control system is communicatively connected to the control system and is configured to receive a signal sent by the control system in response to detecting the first event and lock the microwave source from the first microwave frequency to the second microwave frequency, such that after beam emission is subsequently restored, the error between the first adjustment time of the microwave source and the second adjustment time of the accelerating tube is less than or equal to a third preset threshold. The first adjustment time includes the time required to switch from the second microwave frequency back to the first microwave frequency, and the second adjustment time includes the time required to return from the second operating frequency to the first operating frequency.

[0133] In some embodiments, after the first microwave power of the microwave source is switched to the second microwave power, the method further includes: if the electron linear accelerator beam is restored, after the second microwave power is switched back to the first microwave power, the irradiation dose rate is restored to the level before the beam is stopped within the first time period.

[0134] In some embodiments, the irradiation dose rate control device further includes a pulse voltage switching module configured to switch a first pulse voltage amplitude applied to the microwave source to a second pulse voltage amplitude. The microwave source has a first microwave power under the first pulse voltage amplitude, and has a second microwave power under the second pulse voltage amplitude.

[0135] In some embodiments, the irradiation dose rate control device further includes a power and amplitude pre-determination module, which can execute operations S710 to S730, and will not be described in detail here.

[0136] In some embodiments, the irradiation dose rate control device further includes an adaptation module, which can perform operations S810 to S820, and will not be described in detail here.

[0137] In some embodiments, the irradiation dose rate control device further includes a frequency pre-determination module, which can execute operations S1010 to S1030, and will not be described in detail here.

[0138] In some embodiments, the irradiation dose rate control device further includes a beam recovery module, which can perform operations S1110 to S1120, and will not be described in detail here.

[0139] It can be understood that the control system can call any of the above modules to perform corresponding operations.

[0140] As shown in Figure 12, this embodiment includes a control system 1, an AFC system 2, a microwave excitation source 3, a DC high-voltage power supply 4, a multi-channel fiber optic trigger unit 5, a series switch module 6, a pulse transformer 7, a dual-channel redundant shield on / off switch 8, and a klystron 9. The dual-channel redundant shield on / off switch 8 is one embodiment of the monitoring module. The klystron 9 is one embodiment of the microwave source.

[0141] Accelerator operating parameters and process control are implemented within the accelerator control system / human-machine interface. The AFC system 2 receives enable / disable control from the control system 1, automatically compares the microwave frequencies fed back by the klystron 9 and the accelerator tube, and outputs a drive signal with adjustable positive and negative signals. The microwave excitation source 3 receives the output signal from the AFC system 2 and, based on the signal's positive and negative sign and amplitude, generates a microwave excitation signal source with an output power of approximately 100W and adjustable frequency. The DC high-voltage power supply 4 outputs a DC power supply with a maximum voltage of 1000V as needed. Its output voltage amplitude is controlled by the control system 1, and its output voltage changes relatively slowly. The multi-channel fiber trigger unit 5 receives enable / disable and other signal inputs from the control system 1 and outputs trigger signals for dozens of fiber channels. The series switch module 6 includes IGBT switches equal to the number of output fibers of the multi-channel fiber trigger unit 5. By stacking them in series, the DC high-voltage power supply 4 outputs a voltage several to dozens of times higher. By controlling the on and off of some of the switches, the voltage output can be switched between dozens of levels between pulses. The pulse transformer 7 boosts the output pulse voltage of the series switch module 6 by 11 times. Dual-path redundant shield on / off switch 8 is used to issue hardware control signals as a basis for monitoring the first or second event. Its reliability is crucial, so dual-path redundant feedback is provided to control system 1 regarding the shield on / off status. Klystron 9 converts high-voltage pulse 1 into high-power microwave pulses at the microwave source frequency, which are then transmitted to the accelerating tube.

[0142] In some embodiments, a complete control flow is as follows:

[0143] a. When the shield is opened, the control system 1 receives a signal and sends a prohibition signal to the AFC system 2. The AFC system 2 locks the microwave frequency of the klystron 9 to a predetermined value through the microwave excitation source 3.

[0144] b. The control system 1 sends a control signal to the multi-channel optical fiber trigger unit 5 to turn off several optical fiber signals.

[0145] c. Several IGBT switches in the series switch module 6 are turned off to switch the output voltage.

[0146] d. The high-voltage pulse amplitude drops to the desired level within 1 to 2 microwave pulses, and the klystron 9 outputs microwave pulses to the accelerator tube according to the frequency of the microwave excitation source 3.

[0147] e. When the shield is closed, the control system 1 receives the signal and sends an enable signal to the AFC system 2, and the microwave frequency of the klystron 9 re-tracks the operating frequency of the accelerating tube.

[0148] f. The control system 1 sends a control signal to the multi-channel optical fiber trigger unit 5 to turn on all optical fiber signals.

[0149] g. The series switch module 6 turns on all IGBT switches to restore the original output voltage.

[0150] h. The high-voltage pulse amplitude returns to its original level after 1 to 2 microwave pulses, and the klystron 9 outputs microwave pulses to the accelerator tube according to the frequency of the AFC system 2.

[0151] Fig. 13 schematically shows a block diagram of an electronic device suitable for implementing the irradiation dose rate control method according to an embodiment of the present disclosure. The control system 1 in Fig. 12 may include the electronic device shown in Fig. 13 .

[0152] As shown in Figure 13, the electronic device 1300 according to an embodiment of the present disclosure includes a processor 1301, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 1302 or a program loaded from a storage part 1308 into a random access memory (RAM) 1303. The processor 1301 may include, for example, a general-purpose microprocessor (e.g., a CPU), an instruction set processor and / or a related chipset and / or a dedicated microprocessor (e.g., an application-specific integrated circuit (ASIC)), etc. The processor 1301 may also include an onboard memory for caching purposes. The processor 1301 may include a single processing unit or multiple processing units for performing different actions of the method flow according to an embodiment of the present disclosure.

[0153] The RAM 1303 stores various programs and data required for the operation of the electronic device 1300. The processor 1301, the ROM 1302, and the RAM 1303 are connected to each other via a bus 1304. The processor 1301 executes the various operations of the method flow according to the embodiment of the present disclosure by executing the programs in the ROM 1302 and / or the RAM 1303. It should be noted that the programs may also be stored in one or more memories other than the ROM 1302 and the RAM 1303. The processor 1301 may also execute the various operations of the method flow according to the embodiment of the present disclosure by executing the programs stored in the one or more memories.

[0154] According to an embodiment of the present disclosure, the electronic device 1300 may further include an input / output (I / O) interface 1305, which is also connected to the bus 1304. The electronic device 1300 may further include one or more of the following components connected to the I / O interface 1305: an input portion 1306 including a keyboard, a mouse, etc.; an output portion 1307 including a cathode ray tube (CRT), a liquid crystal display (LCD), a speaker, etc.; a storage portion 1308 including a hard disk, etc.; and a communication portion 1309 including a network interface card such as a LAN card or a modem. The communication portion 1309 performs communication processing via a network such as the Internet. A drive 1310 is also connected to the I / O interface 1305 as needed. A removable medium 1311, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed in the drive 1310 as needed, so that a computer program read therefrom can be installed into the storage portion 1308 as needed.

[0155] The present disclosure also provides a computer-readable storage medium, which may be included in the device / apparatus / system described in the above embodiments. Alternatively, the computer-readable storage medium may exist independently, without being incorporated into the device / apparatus / system. The computer-readable storage medium carries one or more programs, which, when executed, implement the methods according to the embodiments of the present disclosure.

[0156] According to an embodiment of the present disclosure, a computer-readable storage medium may be a non-volatile computer-readable storage medium, such as, but not limited to, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In the present disclosure, a computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in combination with an instruction execution system, apparatus, or device. For example, according to an embodiment of the present disclosure, a computer-readable storage medium may include the ROM 1302 and / or RAM 1303 described above and / or one or more memories other than ROM 1302 and RAM 1303.

[0157] The embodiments of the present disclosure also include a computer program product, which includes a computer program containing program code for executing the method shown in the flowchart. When the computer program product is run in a computer system, the program code is used to enable the computer system to implement the method provided by the embodiments of the present disclosure.

[0158] The computer program executes the above functions defined in the system / device of the embodiment of the present disclosure when the computer program is executed by the processor 1301. According to the embodiment of the present disclosure, the system, device, module, unit, etc. described above can be implemented by a computer program module.

[0159] In one embodiment, the computer program may be stored on a tangible storage medium such as an optical storage device or a magnetic storage device. In another embodiment, the computer program may be transmitted and distributed in the form of a signal over a network medium, downloaded and installed via the communication portion 1309, and / or installed from removable media 1311. The program code contained in the computer program may be transmitted using any appropriate network medium, including but not limited to wireless, wired, or any suitable combination thereof.

[0160] In such an embodiment, the computer program can be downloaded and installed from a network via the communication section 1309 and / or installed from the removable medium 1311. When the computer program is executed by the processor 1301, the above-described functions defined in the system of the embodiment of the present disclosure are performed. According to the embodiment of the present disclosure, the systems, devices, means, modules, units, etc. described above can be implemented by computer program modules.

[0161] According to an embodiment of the present disclosure, the program code for executing the computer program provided by the embodiment of the present disclosure can be written in any combination of one or more programming languages. Specifically, these computer programs can be implemented using high-level procedural and / or object-oriented programming languages, and / or assembly / machine languages. Programming languages ​​include, but are not limited to, languages ​​such as Java, C++, python, "C" or similar programming languages. The program code can be executed entirely on the user computing device, partially on the user device, partially on a remote computing device, or entirely on a remote computing device or server. In cases involving a remote computing device, the remote computing device can be connected to the user computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computing device (for example, using an Internet service provider to connect via the Internet).

[0162] One or more of the above embodiments can achieve at least some of the following beneficial effects:

[0163] (1) By monitoring specific events, cutting off the electron gun pulse and switching the power of the microwave source, the dark current level in the accelerating tube can be effectively controlled to avoid the generation of dark current that hits the target after acceleration to generate X-rays, thereby making the leakage dose rate of the irradiation safety margin less than or equal to the first preset threshold, avoiding an excessively high leakage dose rate and meeting the radiation protection requirements.

[0164] (2) Taking into account the second adjustment time required for the accelerating tube to return to its normal operating frequency when emitting beams, the efficiency of the microwave source's microwave frequency tracking the accelerating tube's operating frequency is improved, and the microwave source is locked to the second microwave frequency, so that after the beam is subsequently restored, the first adjustment time of the microwave source is as close as possible to the changing time of the accelerating tube's operating frequency, thereby reducing the recovery time of the irradiation dose rate.

[0165] (3) A solution is provided for switching the microwave power to an appropriate value to balance dark current magnitude and dose rate stability. The operation of switching the first microwave power of the microwave source to the second microwave power not only controls the dark current level in the accelerating tube but also takes into account the recovery time of the irradiation dose rate, thereby achieving the technical effect of switching the second microwave power to an appropriate level to balance dark current magnitude and dose rate stability.

[0166] The flowcharts and block diagrams in the accompanying drawings illustrate the possible implementation architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each box in the flowchart or block diagram can represent a module, program segment, or a part of code, and the above-mentioned module, program segment, or a part of code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flowchart, and the combination of boxes in the block diagram or flowchart, can be implemented with a dedicated hardware-based system that performs the specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0167] Those skilled in the art will appreciate that the features described in the various embodiments and / or claims of this disclosure may be combined and / or coupled in various ways, even if such combinations and / or couplings are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure may be combined and / or coupled in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or couplings are intended to fall within the scope of this disclosure.

[0168] The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be used in combination to advantage. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A method for controlling irradiation dose rate, which is used for an electron linear accelerator including a microwave source, an electron gun, and an accelerating tube. The method includes: When the electron linear accelerator emits beams, monitoring a first event for indicating a change in beam emission parameters, where the beam emission parameters include the pulse of the electron gun and the microwave power of the microwave source, and the first event is determined by irradiation protection requirements; In response to monitoring the first event, cutting off the pulse of the electron gun and switching the first microwave power of the microwave source to a second microwave power, so that the leakage dose rate of the irradiation safety boundary is less than or equal to a first preset threshold; Wherein, the dark current level in the accelerating tube under the second microwave power is less than or equal to a second preset threshold.

2. The method according to claim 1, wherein, The accelerating tube has a first operating frequency when emitting beams and a second operating frequency after the microwave source is switched to the second microwave power, and the beam emission parameters further include the microwave frequency of the microwave source; In response to monitoring the first event, the method further includes: Locking the microwave source from the first microwave frequency to the second microwave frequency, so that after subsequent beam emission resumes, the error between the first adjustment time of the microwave source and the second adjustment time of the accelerating tube is less than or equal to a third preset threshold; Wherein, the first adjustment time includes the time for switching back from the second microwave frequency to the first microwave frequency, and the second adjustment time includes the time for recovering from the second operating frequency to the first operating frequency.

3. The method according to claim 1 or 2, wherein After switching the first microwave power of the microwave source to the second microwave power, the method further includes: If the electron linear accelerator resumes beam emission, after switching the second microwave power back to the first microwave power, the irradiation dose rate resumes to the level before beam emission stop within a first time period.

4. The method according to claim 1 or 2, wherein, Switching the first microwave power of the microwave source to the second microwave power includes: Switching the amplitude of the first pulse voltage acting on the microwave source to the amplitude of a second pulse voltage; Wherein, the microwave source has a first microwave power under the action of the first pulse voltage amplitude and a second microwave power under the action of the second pulse voltage amplitude.

5. The method according to claim 4, wherein, Before switching the amplitude of the first pulse voltage acting on the microwave source to the amplitude of the second pulse voltage, the method further includes: Determining a first correspondence relationship between the dark current of the accelerating tube and the microwave power of the microwave source; Determining a second correspondence relationship between the microwave power difference of the microwave source and the irradiation dose rate recovery time, where the microwave power difference includes the difference between the first microwave power and the second microwave power, and the irradiation dose rate recovery time includes the time for recovering to the level before beam emission stop; Determining the second microwave power and the amplitude of the second pulse voltage based on the first correspondence relationship and the second correspondence relationship.

6. The method according to claim 5, wherein At least two pulse voltage amplitudes adapted to different accelerating tubes are pre-stored. Switching the amplitude of the first pulse voltage acting on the microwave source to the amplitude of the second pulse voltage includes: Determine a first pulse voltage amplitude and a second pulse voltage amplitude adapted to the accelerating tube from the at least two pulse voltage amplitudes; During a second time period, switch the first pulse voltage amplitude applied to the microwave source to the second pulse voltage amplitude.

7. The method according to claim 2, wherein Before locking the microwave source from a first microwave frequency to a second microwave frequency, the method further includes: Determine the second adjustment time of the accelerating tube; Determine a first adjustment time of the microwave source based on the second adjustment time and the third preset threshold; Determine the second microwave frequency based on the first adjustment time.

8. The method according to claim 1 or 2, wherein The electron linear accelerator further includes a shielding device, and the accelerating tube is placed inside the shielding device for beam output; Wherein, monitoring the first event for indicating a reduction in the irradiation dose rate includes: Monitoring the event that the shielding device is opened.

9. The method according to claim 8, wherein The shielding device includes a shielding body and a shielding plug. One side wall of the shielding body has an opening. When the shielding device is closed, the shielding plug is inserted into the opening, and the irradiated object enters and exits the shielding device through the opening; Wherein, monitoring the event that the shielding device is opened includes: Monitoring the event that the shielding plug is pulled out of the opening.

10. The method according to claim 1 or 2, wherein After cutting off the pulse of the electron gun, the method further includes: Monitoring a second event for indicating the restoration of the beam output parameters, the second event being triggered in response to the elimination of the first event; In response to monitoring the second event, restore the pulse of the electron gun, and switch the second microwave power of the microwave source to the first microwave power to make the electron linear accelerator resume beam output.

11. The method according to claim 10, wherein The electron linear accelerator further includes an automatic frequency control system for locking the microwave source from a first microwave frequency to a second microwave frequency; In response to monitoring the second event, the method further includes: Enable the automatic frequency control system to switch the microwave source from the second microwave frequency back to the first microwave frequency to follow the first operating frequency of the accelerating tube.

12. An irradiation dose rate control device for an electron linear accelerator including a microwave source, an electron gun, and an accelerating tube, the device includes: A monitoring module for monitoring, when the electron linear accelerator outputs a beam, a first event for indicating a change in the beam output parameters, wherein the beam output parameters include the pulse of the electron gun and the microwave power of the microwave source, and the first event is determined by irradiation protection requirements; A control system communicatively connected to the monitoring module for, in response to monitoring the first event, cutting off the pulse of the electron gun and switching the first microwave power of the microwave source to a second microwave power so that the leakage dose rate of the irradiation safety boundary is less than or equal to a first preset threshold; Wherein, the dark current level in the accelerating tube under the second microwave power is less than or equal to a second preset threshold.

13. The device according to claim 12, wherein The accelerating tube has a first operating frequency when the beam exits, and has a second operating frequency after the microwave source is switched to a second microwave power. The beam output parameters further include the microwave frequency of the microwave source; The device further comprises: an automatic frequency control system, communicatively connected to the control system, configured to receive a signal sent by the control system in response to detecting the first event, and lock the microwave source from a first microwave frequency to a second microwave frequency, such that after subsequent beam output resumes, the error between the first adjustment time of the microwave source and the second adjustment time of the accelerating tube is less than or equal to a third preset threshold; wherein, the first adjustment time includes the time for switching back from the second microwave frequency to the first microwave frequency, and the second adjustment time includes the time for recovering from the second operating frequency to the first operating frequency.

14. An electron linear accelerator, comprising: an accelerating tube; an electron gun, configured to generate an electron beam and inject it into the accelerating tube; a microwave source, configured to generate microwaves and inject them into the accelerating tube to accelerate the electron beam; a target, configured to convert the accelerated electron beam into a beam of rays; the irradiation dose rate control device according to claim 12 or 13.

15. An irradiation device, comprising the electron linear accelerator according to claim 14.

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