Double-modulator control system of medical electron linear accelerator

Abstract

The invention discloses a double-modulator control system of a medical electron linear accelerator. The double-modulator control system comprises a magnetron modulator, a grid-controlled electron gun modulator, a magnetron, a grid-controlled electron gun, an accelerating tube, three microwave detection circuits, a feedback microwave system, a therapeutic head, an automatic dosage control system and a digital signal processing system; the digital signal processing system is connected with the magnetron modulator and the grid-controlled electron gun modulator respectively, the magnetron modulator is connected with the magnetron, a microwave detection circuit is connected between the magnetron and the feedback microwave system, and the other two microwave detection circuits are connected between the inlet and the outlet of the accelerating tube and the feedback microwave system respectively; and the magnetron modulator, the three microwave detection circuits and the automatic dosage control system are connected with the digital signal processing system respectively, and the electron gun modulator is sequentially connected with the grid-controlled electron gun, the accelerating tube and the therapeutic head. The double-modulator control system realizes independent control, and can dynamically adjust the emission capacity of the electron gun in real time.

Description

technical field [0001] The invention relates to a medical electron linear accelerator, in particular to a modulator of a medical electron linear accelerator, and belongs to the technical field of medical electron linear accelerator control Background technique [0002] Medical accelerators refer to accelerators specially used in clinical medicine. The current representative of medical accelerators is medical electron linear accelerators. Medical electron linear accelerators are not only the type with the largest number of accelerators, but also the type with the largest number of various radiation therapy devices. Medical electron linear accelerator is the most important radiation therapy device. [0003] In an accelerator using a microwave electric field to accelerate electrons, in order to obtain an accelerating electric field as high as possible, the instantaneous microwave power is very large, reaching the order of MW, so the microwave source works in pulses, and the pul...

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Problems solved by technology

In addition, the high-frequency component is transmitted to each low-voltage control system of the system through the gate control power supply (communication cable between the AIC system and the main control system), resulting in unstable communication of the system

[0008] (3) The structure of the electron gun determines that there is a certain distributed capacitance between the cathode grid assembly and the anode of the electron gun. This capacitance couples the high-voltage pulse to the electron gun grid, resulting in the fact that the first 1 μs of each grid control pulse cannot basically control the emission beam. Makes it difficult to precisely control and adjust the electron beam flow to the best state

[0009] (4) The high voltage pulse of the magnetron and the high voltage pulse of the electron gun use the same pulse transformer. The trailing edge of the high voltage pulse is limited by the characteristics of the magnetron, resulting in a very long (over 8μs), and the modulator system does not have the cutting function of the trailing edge. In addition, For the high-voltage pulse with such a large trailing edge component, there is no mature technology in China to cut the trailing edge

[0010] (5) Because the same pulse transformer is used, the pulse high voltage amplitude of the gate-controlled electron gun is limited by the working state of the magnetron, and the high voltage required by the electron gun cannot be given separately, and the obtained high voltage cannot reach the specified working state of the electron gun

As a result, the beam current emitted by the electron gun is small. In actual use, the filament current of the electron gun is increased to meet the requirements of the system, which greatly shortens the service life of the electron gun.

In addition, the initial velocity of the beam emitted by the electron gun cannot be controlled, and it is difficult to meet the technical requirements of the ultra-wide energy range medical electron linear accelerator for the controllable initial velocity of the beam injected into the inner cavity of the accelerating tube.

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