What is a Kinetic Energy Penetrator?

An accelerator is a device that increases the speed (kinetic energy) of charged particles. Accelerators can be used in nuclear experiments, radiomedicine, radiochemistry, radioisotope manufacturing, non-destructive flaw detection, etc. The increased energy of particles is generally above 0.1 megaelectron volts. There are many types of accelerators, including cyclotrons, linear accelerators, electrostatic accelerators, particle accelerators, and voltage doublers.

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The charged particles will be accelerated by the electromagnetic force in the electric field to increase the energy. Electric fields can exist in three different forms: electrostatic fields, magnetically induced electric fields, and alternating electromagnetic fields. Accelerators are developed based on the principle of accelerating charged particles using these three types of electric fields. Since the 1930s, after more than 70 years of development, many types of accelerators have appeared, and their classification standards are also many. For example, according to the types of accelerated particles, they can be divided into electron accelerators, protons and heavy ion accelerators, and microparticles (powders) , Dust, etc.) accelerators (also known as particle cluster accelerators); Accelerated particle energy can be divided into low-energy accelerators (energy below 100MeV), medium-energy accelerators (energy between 100MeV ~ 1GeV) and high-energy accelerators (energy 1 ~ 100GeV), energy Above 100 GeV is called ultra-high energy accelerator; according to beam intensity, it can be divided into strong current accelerator (beam intensity above 1mA), medium current accelerator (beam intensity above 10A ~ 1mA) and low current accelerator (beam intensity below 10A ); According to the type of acceleration electric field can be divided into high-voltage type accelerator, electromagnetic induction type accelerator and high-frequency resonance type accelerator; according to the shape of particle motion orbit can be divided into linear accelerator and circular (or ring) accelerator. Linear accelerators include DC high-voltage accelerators and RF colliders. Circular accelerators include cyclotrons, phase-stable accelerators, electronic induction accelerators, synchrotrons, weak-focus synchronous phase-stable accelerators, strong-focus synchronous phase-stable accelerators, and ring colliders. ^[1]

An accelerator is a complex device that consists of the following four basic components:

(1) Particle source

Such as electron gun, ion source, etc., used to provide the charged particle beam that needs to be accelerated.

(2) Vacuum acceleration structure

Such as the acceleration tube] radio frequency acceleration cavity and annular acceleration chamber, etc., generate a certain acceleration electric field in a vacuum, so that particles are accelerated.

(3) Guided focusing system

A certain electromagnetic field is used to guide and restrain the accelerated particle beam to accelerate it along a certain trajectory, such as the dominant magnetic field of a circular accelerator.

(4) Beam transport and analysis system

A system consisting of an electron, a magnetic field lens, a bending magnet, and an electric and magnetic field analyzer, used to transport and analyze a charged particle beam between a particle source and an accelerator.

In addition, there are auxiliary systems such as beam monitoring devices, electromagnetic stability control devices, vacuum devices, and electrical equipment operating equipment. ^[1]

Early exploration of the accelerator dates back to the 1920s. As early as 1919 British scientists

In 1945, former Soviet scientist Wixler and American scientist McMillan independently discovered the principle of automatic phase stabilization. In 1946, the first phase-stable accelerator was completed in Berkeley, and a series of synchrotrons have been born since then, including synchrocyclotrons. This is the first revolution in accelerator development. In 1952, American scientists Cologne, Livingston, and Schneider put forward the principle of strong focusing, which has since been widely used in circular accelerators and linear accelerators. This is the second revolution in accelerator development. In 1960, Tauchek first proposed the concept of a collider, that is, two particles were injected into the synchrotron in opposite directions and collided at a specified position. Under his leadership, he built a The 1-meter-diameter collider called AdA opened a new era in the development of accelerators. This is the third revolution in accelerator development. ^[1]

1955

The 700eV proton electrostatic accelerator was built by the Institute of Atomic Energy, Chinese Academy of Sciences.

The research on the structure of matter under the condition of high-energy accelerator is essentially related to the relative change (transformation) of the energy state between natural energy groups (or energy clusters and energy ions) in the natural state.

The application of low-energy accelerators is an important branch of nuclear technology applications. Currently, most of the thousands of accelerators running around the world are low-energy accelerators that have been widely used in industrial, agricultural, medical, and other fields. The application of low-energy accelerators in these fields has greatly changed the face of these fields and created huge economic and social benefits.

Accelerator industry

1) Irradiation processing

The application of electron beams or X-rays produced by accelerators for irradiation processing has become an important means and process of production in chemical, electric power, food, environmental protection and other industries, and is a new processing technology. It is widely used in polymer cross-linking modification, coating curing, polyethylene foaming, heat-shrinkable materials, semiconductor modification, wood-plastic composite material preparation, food sterilization and preservation, flue gas desulfurization and denitration, and other processing processes. .

The products produced by irradiation have many excellent characteristics. For example, the electrical and thermal properties of polyethylene cables are greatly improved after being irradiated with a dose of 105Gy. The temperature before use is 60 ~ 70 ° C. Long-term use temperature can reach above 120 . At present, China has more than 40 production lines using accelerators for irradiation processing.

2) Non-destructive testing

Non-destructive testing is to detect the internal conditions of materials, products or components without damaging and damaging them, and to determine whether there are defects inside. There are many modern non-destructive testing methods, such as: ultrasonic flaw detection method, eddy current flaw detection method, fluorescent flaw detection method and ray detection method. The radiographic inspection method can inspect both the surface of the workpiece and the defects inside the workpiece. The equipment can use gamma rays produced by the radioisotope Co-60, low-energy X-rays produced by X-ray machines, and high-energy X-rays produced by electron accelerators. Especially the flaw detection accelerator has high penetration ability and sensitivity. It is used as a final inspection method or other verification methods for verification and in quality control, in large-scale cast and forged weldments, large pressure vessels, reactor pressure shells, and rocket solid fuels. It is widely used in defect inspection of workpieces. This flaw detection accelerator is based on an electronic linear accelerator.

The methods of radiographic inspection can be divided into three types according to the different methods of receiving and processing the rays transmitted through the workpiece:

a. Radiography

This method is similar to the X-ray film taken during our physical examination. The radiographic receiver is X-ray film. When detecting a flaw, place the film box containing the X-ray film against the back of the workpiece to be inspected. After irradiating the workpiece with X-rays, the film is sensitized through the rays of the workpiece, and the real situation inside the workpiece is reflected on the latex of the film After processing the photosensitive film, you can clearly understand whether there are defects in the workpiece and the type, location, shape and size of the defects.

b, radiation imaging

The radiation receiver of this method is an array detector or a fluorescence-sensitized screen. The former is a large container inspection product jointly developed and produced by Tsinghua University and Tsinghua Tongfang. The latter is an X-ray security inspection system for luggage and parcels at airports, railways, and non-destructive inspection in industry. This method, coupled with an image processing system, can display the real situation inside the item online in real time.

c. Industrial CT

Similar to the principle of medical CT, CT technology is computer-assisted tomography. CT technology, which uses an accelerator as an X-ray source, is an advanced non-destructive testing method, which is mainly developed for the detection of large solid rocket engines and precision workpieces. Its density resolution can reach 0.1%, which is an order of magnitude higher than conventional radiation technology. It has important application value in defect detection, dimensional measurement, and assembly structure analysis of precision workpieces in the fields of aerospace, aviation, weapons, and automobile manufacturing.

3) Ion implantation

Accelerators can be used to implant ions of a certain energy into the surface layer of solid materials to obtain good physical, chemical and electrical properties. Semiconductor devices, metal material modification, and large-scale integrated circuit production all use ion implantation technology. China now has more than 100 ion implanters of various types. Among them, China has produced more than 140 ion implanters with an energy of 150KeV ~ 600KeV (1KeV = 1 × 10 ³ eV) and a current intensity of 0.5mA to more than ten mA.

Accelerator agriculture

The application of accelerators as nuclear technology application equipment in agriculture has been widely used in some countries in three main areas:

1) Irradiation breeding

The application of accelerators in radiation breeding is mainly to use high-energy electrons, X-rays, fast neutrons or protons generated by it to irradiate crop seeds, buds, embryos, or grain pollen, etc., to change the genetic characteristics of crops, so that they are optimized development of. Breeding breeds through radiation mutation has played a significant role in improving yield, improving quality, shortening growth period, and enhancing stress resistance. Potatoes, wheat, rice, cotton, soybeans and other crops after irradiation breeding can have the advantages of high yield, early maturity, short stalks and resistance to diseases and insect pests.

2) Irradiation preservation

Irradiation preservation is a new preservation technology developed after traditional preservation methods such as heat treatment, dehydration, refrigeration, and chemical processing. For example, irradiated potatoes, garlic, onions, etc. can inhibit their germination and extend the storage period; dried and fresh fruits, mushrooms, sausages, etc., can extend the supply period and shelf life.

3) Irradiation and sterilization

At present, chemical fumigation methods are commonly used in pesticide and sterilization of agricultural products and foods. Due to the residual toxicity caused by the use of chemical fumigation methods such as methyl bromide and ethylene oxide, and damage to the atmospheric ozone layer, according to the Montreal Convention, it will be used worldwide by 2005 The use of methyl bromide is prohibited within the scope. Therefore, the use of accelerators for agricultural products, food and other irradiation to kill insects and sterilization has developed rapidly. The use of high-energy electrons or X-rays generated by the accelerator can kill parasites and pathogenic bacteria in agricultural products and food, which can not only reduce the loss of food due to spoilage and pests, but also improve the quality of food hygiene and added value.

Accelerator health

With the advancement of science and technology and the improvement of people's life and quality, people have put forward higher requirements for medical and health conditions. The application of accelerators in medical care has promoted the development of medicine and the extension of human life. At present, there are three main applications of accelerators in medical and health, namely radiation therapy, production of medical isotopes, and disinfection of medical devices, medical supplies and drugs.

1) Radiation therapy

Medical accelerators for malignant tumor radiotherapy (referred to as radiotherapy) are the largest and most mature technology in various application fields of accelerators in the world today.

Accelerators for radiotherapy have been developed from induction accelerators in the 1950s to medical electronic cyclotrons in the 1960s, and medical electronic linear accelerators gradually dominated in the 1970s. Currently, more than 3,000 medical electronic linear accelerators are equipped in hospitals around the world.

In addition to the use of electron beams and X-rays generated by accelerators for radiation therapy, accelerators can also be used for proton, neutron, heavy ion, and meson radiotherapy. These cancer treatment methods are still in the experimental stage. Significant effect. However, these accelerators have much higher energy, more complicated structures, and are much more expensive than electronic linear accelerators.

The use of electronic linear accelerators for stereotactic radiotherapy, commonly known as X-knife, is a new radiotherapy technology developed over the years. Compared with conventional radiotherapy, this technique can protect 15% ~ 20% of normal tissues, and tumors can increase the dose by 20% ~ 40%, which can more effectively kill cancer cells and increase the efficacy of radiotherapy.

In the 1960s, Chinese hospitals were equipped with medical induction accelerators, and in the mid-1970s, medical electronic linear accelerators began to be installed in hospitals throughout China. As of early 2000, China has about 530 medical accelerators of various energies, including about 230 domestic medical accelerators and about 300 imported medical accelerators.

2) Medical isotope production

Modern nuclear medicine widely uses radioisotopes to diagnose diseases and treat tumors. About 80 isotopes have been identified as clinical applications, of which two-thirds are produced by accelerators, especially short-lived isotopes that can only be produced by accelerators. These short-lived isotopes are mainly used in the following areas:

a. Positron and single photon emission computed tomographyPET and SPECT

PET is inhaled or pre-injected by the patient with a very short half-life of positron-emitting radionuclides. These detectors are used to detect positrons and photons emitted from annihilation from various angles by a circularly arranged detector. The computer-processed reconstruction An image of the cut tissue. These short-lived radionuclides are made by small cyclotrons. The shortest half-life nuclides, such as O-15, are only 123 seconds, usually several minutes to one hour. Therefore, such accelerators are generally equipped in hospitals using PET. Small cyclotrons that produce short-lived radionuclides for PET have attracted many accelerator manufacturers to develop them. At present, dozens of small cyclotrons produced by several foreign accelerator manufacturers have reached.

b. Image acquisition

Using radionuclide scintillation scanning or gamma photography to acquire images can diagnose tumors, examine human organs, study their physiological and biochemical functions and metabolic status, and obtain dynamic data. For example, Tl-201 is used for myocardial examination, and it is currently the most sensitive inspection method for the early detection of coronary heart disease and the location of myocardial infarction. Most of these radionuclides are also produced by accelerators.

3) Irradiation disinfection

The use of accelerators to sterilize and sterilize medical instruments, disposable medical articles, vaccines, antibiotics, and proprietary Chinese medicines is a promising future for accelerators in medical and health applications. Similar to the introduction of the insecticidal and sterilization principles of accelerators in food, it can replace the currently applied methods of high temperature disinfection and chemical disinfection. However, the dose of radiation required for sterilization is greater than that required for insecticide.