Accelerator tube: the core of high-energy physics and medical technology

Accelerator tubes, as key components of accelerators, play an irreplaceable role in physics research, industrial applications, and medical technology. This article will delve into the basic principles, structural design, working mechanism, and applications of accelerator tubes in various fields, especially their important role in medical accelerators.


1、 Basic concepts and classification of acceleration tubes

The accelerating tube, also known as the accelerating tube, is the core component of an accelerator. Its main function is to accelerate particles (such as electrons, protons, etc.) injected from an electron gun or ion source to a high-energy state under the action of an electric field. According to the different acceleration methods, acceleration tubes can be divided into various types, such as electrostatic acceleration tubes, microwave acceleration tubes (including standing wave acceleration tubes and traveling wave acceleration tubes), etc. Among them, microwave accelerator tubes have been widely used in modern accelerators due to their efficient and compact structure.

1. Electrostatic accelerator tube

Electrostatic accelerator tubes mainly use electrostatic fields to accelerate particles. Its structure is relatively simple, mainly composed of accelerating electrodes and insulating materials. After being emitted from an ion source or electron gun, particles enter an accelerator tube and gradually accelerate under the action of an electrostatic field. However, due to the limitations of the electrostatic field, the acceleration ability of electrostatic accelerator tubes is limited, making them suitable for situations where there is not a high demand for acceleration energy.

2. Microwave accelerator tube

Microwave accelerator tubes use microwave electric fields to accelerate particles. Compared with electrostatic accelerator tubes, microwave accelerator tubes have higher acceleration efficiency and a wider acceleration range. According to the different acceleration methods, microwave accelerators can be divided into two types: standing wave accelerators and traveling wave accelerators. A standing wave accelerator uses a standing wave electric field to accelerate particles, while a traveling wave accelerator uses a traveling wave electric field for acceleration. Both have their own advantages and disadvantages, and are suitable for different application scenarios.


2、 The working principle of the accelerator tube

The working principle of an accelerator tube involves multiple complex processes, mainly including constructing a vacuum environment, generating electron beams, electron beam acceleration, and generating therapeutic rays.

1. Building a vacuum environment

The work of the accelerator tube needs to be carried out in a highly vacuum environment. This is because molecules in the air collide with accelerating particles, resulting in energy loss and beam scattering. In order to maintain a vacuum environment, acceleration tubes typically use multi-stage exhaust systems and titanium pumps for exhaust and degassing. At the same time, the vacuum detection circuit will monitor and control the vacuum degree inside the accelerator tube in real time, ensuring its optimal operation.

2. Generating an electron beam

The electron beam is the main object of acceleration for the accelerator tube. At one end of the accelerator tube, the electron gun generates electrons by heating the cathode. These electrons move towards the cavity of the accelerating tube under the pulse voltage provided by the modulator. After entering the accelerator tube, the electron beam passes through the initial focusing and acceleration of the focusing cavity, forming an electron flow with a certain energy and width.

3. Electron beam acceleration

The acceleration process of an electron beam in an accelerator tube is its core function. Inside the accelerator tube, a specific electric field distribution is designed to ensure that the electron beam can accelerate uniformly along the axis direction. For a microwave accelerator tube, its electric field is generated by a microwave power source and propagates along the axis of the accelerator tube. The electron beam continuously obtains energy under the action of an electric field, ultimately reaching a high-energy state.

4. Generate therapeutic radiation

In medical accelerators, the accelerated electron beam can be directly used for the treatment of superficial tumors (known as electron beam therapy). In addition, electron beams can also bombard heavy metal targets (such as tungsten targets), generating high-energy X-rays through bremsstrahlung. These X-rays have stronger penetration and can be used for the treatment of deep tumors.

3、 Structural Design of Acceleration Tube

The structural design of the acceleration tube has a significant impact on its performance. Modern acceleration tubes often use flat electrode designs to improve the uniformity and stability of the acceleration electric field. At the same time, in order to reduce the interaction between the beam and the insulation wall, the ratio of the beam aperture of the accelerating tube to the electrode spacing needs to be kept sufficiently large.

1. Acceleration electrode

The acceleration electrode is one of the core components of the acceleration tube. Its shape and arrangement directly affect the electric field distribution and acceleration effect. Modern acceleration tubes often use flat electrode designs, which are conducive to forming a uniform acceleration electric field. At the same time, in order to reduce beam scattering and energy loss, special treatment is required on the surface of the accelerating electrode to improve its smoothness and conductivity.

2. Vacuum system

The vacuum system is the key to maintaining a high vacuum environment inside the accelerator tube. It mainly includes components such as exhaust system, titanium pump, vacuum detection circuit, etc. The exhaust system is responsible for exhausting the air inside the acceleration tube and maintaining a certain degree of vacuum; Titanium pumps use orthogonal electromagnetic fields to transform air molecules into charged particles and expel them through the action of electric fields; The vacuum detection circuit monitors and controls the vacuum degree inside the accelerator tube in real-time to ensure its optimal operation.


3. Microwave power source

For microwave accelerator tubes, the microwave power source is an important component. It is responsible for generating and transmitting microwave electric fields to drive electron beam acceleration. Common microwave power sources include klystrons, magnetrons, etc. These devices have efficient and stable characteristics that can meet the needs of different acceleration tubes.

4、 The application of accelerator tubes in the medical field

The application of accelerator tubes in the medical field is mainly reflected in medical accelerators. Medical accelerators have become an important treatment method for tumors by utilizing high-energy radiation generated by accelerator tubes for radiation therapy.