The application of accelerator-generated electron beams or X-rays for irradiation processing has become an important means and process for the production of chemical, electric power, food, environmental protection and other industries, is a new processing technology process. It is widely used in polymer crosslinking modification, coating curing, polyethylene foaming, heat-shrinkable materials, semiconductor modification, wood-plastic composite material preparation, food sterilization and preservation, flue gas irradiation desulfurization and denitrification and other processing.
The irradiated products have many excellent characteristics, for example: irradiated cross-linked polyethylene cable irradiated by 105Gy dose, its electrical properties, thermal properties have greatly improved the use of the temperature before irradiation of 60 ~ 70 ℃, irradiation of long-term use of the temperature up to 120 ℃ or more. In China, there are more than 200 production lines of irradiation processing with gas pedals. Non-destructive testing is in the case of materials, products or components without damage and without destroying them, you can detect their internal conditions, to determine whether there are internal defects. There are many modern non-destructive testing methods, such as: ultrasonic flaw detection, eddy current detection, fluorescence detection and ray detection. Ray detection method can check the surface of the workpiece and can check the defects inside the workpiece. Equipment can be used to produce the radioisotope Co60 γ-rays, X-ray machines produce low-energy X-rays and high-energy X-rays produced by the electron gas pedal. Especially the penetrating ability and high sensitivity of the flaw detection gas pedal, as a means of final inspection or other methods of flaw detection means of verification and in the quality control, in the large casting and forging weldments, large pressure vessels, reactor pressure shells, rockets, such as solid fuel defects in the inspection of the workpiece has been widely used. This kind of flaw detection gas pedal to electronic linear gas pedal as the main model.
Ray detection methods according to the through the workpiece of the ray acceptance and processing methods, and can be divided into three kinds of ray detection method:
a, radiographic method
This method is similar to our physical examination X-ray film, the ray acceptor is X-ray film. Detection, will be equipped with X-ray film film box immediately behind the workpiece being examined, with X-rays on the workpiece after irradiation, the rays through the workpiece to make the film sensitized, and at the same time the real situation inside the workpiece is reflected to the film on the latex, after the sensitized film processing, you can clearly understand the workpiece with or without defects as well as defects in the type, location, shape and size.
b, radiation imaging method
This method of ray receiver is an array detector or fluorescence sensing screen. The former is Tsinghua University and Tsinghua Tongfang *** with the development and production of large container inspection series products. The latter is used in airports, railroads, baggage, parcel X-ray security system, can also be used for industrial non-destructive testing. This method with the image processing system can be online real-time display of the real situation inside the items.
c, industrial CT
With medical CT principle is similar, CT technology that is computer-aided tomography. Selected gas pedal as the X-ray source of CT technology is an advanced means of non-destructive testing, mainly for large solid rocket motors and precision workpiece testing and development. It has a density resolution of up to 0.1%, which is an order of magnitude higher than conventional ray technology. In aerospace, aviation, weapons, automobile manufacturing and other fields of precision workpiece defect detection, size measurement, assembly structure analysis and other important applications. The use of gas pedals to inject ions of a certain energy into the surface layer of solid materials can obtain good physical, chemical and electrical properties. Semiconductor devices, metal material modification and large-scale integrated circuit production are applied to ion implantation technology. China now has more than 100 sets of various types of ion implantation machine. China's own cumulative production of more than 140 sets of ion implantation machine, the energy of 150KeV ~ 600KeV (1KeV = 1 × 103eV), the current strength of 0.5mA to dozens of mA.
1.2 Low-energy gas pedal in agriculture
As the application of nuclear technology application equipment gas pedal applications in agriculture, the general use of a number of countries have been obvious There are three main economic benefits:
1) irradiation breeding
The application of gas pedal in irradiation breeding, mainly using it to produce high-energy electrons, X-rays, fast neutrons or protons irradiation of crop seeds, buds, embryos or grain pollen, etc., to change the genetic characteristics of crops, so that they are optimized along the direction of development. Selection and breeding of good seeds through radiation mutagenesis has played a significant role in increasing yields, improving quality, shortening the growing period, and enhancing resistance to adversity. Potato, wheat, rice, cotton, soybean and other crops after irradiation breeding can have high yield, early maturity, dwarf and pest resistance and other advantages.
2) irradiation preservation
Irradiation preservation is following the heat treatment, dehydration, refrigeration, chemical processing and other traditional preservation methods, the development of a new preservation technology. For example, on potatoes, garlic, onions, etc. after irradiation treatment, can inhibit its germination, extend the storage period; on dry and fresh fruit, mushrooms, sausages, etc. after irradiation treatment, can extend the supply period and shelf life.
3) irradiation insecticide, sterilization
, in agricultural products, food and other insecticidal sterilization commonly used chemical fumigation, due to the use of bromomethane, ethylene oxide and other chemical fumigation caused by residual toxicity, destruction of the atmospheric ozone layer, etc., according to the Montreal Convention, by 2005, the use of bromomethane to be banned on a global scale. As a result, the use of gas pedals for irradiation of agricultural products and foodstuffs to kill pests and sterilize them has developed rapidly. The use of accelerator-generated high-energy electrons or X-rays can kill parasites and pathogenic bacteria in agricultural products and food, which not only reduces the loss of food due to corruption and pests, but also improves the hygiene grade and added value of food. With the progress of science and technology, people's life and quality of life, people put forward higher requirements for medical and health conditions. And the application of gas pedal in healthcare promotes the development of medicine and the extension of human life. At present, the application of gas pedal in healthcare mainly has three aspects, namely, radiation therapy, medical isotope production and sterilization of medical devices, medical supplies and drugs.
1) Radiotherapy
Medical gas pedals used for radiation therapy of malignant tumors (referred to as radiotherapy) are the largest in number and the most technologically mature among the various applications of gas pedals in the world today.
The gas pedal used for radiotherapy is the induction gas pedal in the 50's, the medical electronic cyclotron in the 60's, and the medical electronic linear gas pedal in the 70's. The world has about 3,000 accelerators, which are used for radiotherapy of malignant tumors.
In addition to the application of accelerator-generated electron beams and X-rays for radiotherapy, gas pedals can also be used for proton radiotherapy, neutron radiotherapy, heavy ion radiotherapy and π meson radiotherapy, etc. These cancer treatment methods are still in the experimental stage, and the results of the experiments show that the therapeutic efficacy is remarkable. However, these gas pedals are much higher in energy than electron linear gas pedals, much more complex in structure and much more expensive, and have not been popularized yet.
The use of electron linear gas pedals to carry out stereotactic radiotherapy, commonly known as X-knife, the development of new radiotherapy technology. This technique, compared with conventional radiotherapy, can protect 15% to 20% more normal tissue, while the tumor increases the dose by 20% to 40%, which can kill cancer cells more effectively, thus increasing the efficacy of radiotherapy.
In the 1960s, China's hospitals were equipped with medical induction gas pedals, and in the mid-1970s, medical electronic linear gas pedals began to equip hospitals around China. As of the beginning of 2000, China has a variety of energy medical gas pedal about 530 units, of which about 250 sets of domestic medical gas pedal, imported medical gas pedal about 300 units. Modern nuclear medicine Widely used radioisotopes for diagnosis of diseases and treatment of tumors, about 80 kinds of isotopes have been identified for clinical application, of which 2/3 are produced by gas pedals, especially short-lived isotopes lacking neutrons can only be produced by gas pedals. These short-lived isotopes are mainly used in the following applications:
a. Positron and single photon emission computed tomography-PET and SPECT
PET is a procedure in which the patient inhales or pre-injects radionuclides that emit positrons with a very short half-life, and detects these radionuclides at all angles by means of detectors placed in a ring. The photons emitted by these radionuclides are detected from all angles by a ring-placed detector that emits positrons and photons when they annihilate, and the images of the cut tissues are reconstructed by a computer after processing. These short-lived radionuclides are prepared by small cyclotrons. The shortest half-life nuclides such as 15O are only 123 seconds, usually a few minutes to about an hour. Therefore, such gas pedals are generally equipped in hospitals where PET is used. The production of PET-specific short-lived radionuclides of small cyclotron, attracted a number of gas pedal manufacturers to develop research and development. , Several foreign gas pedal manufacturers have reached dozens of small cyclotron production.
b, image acquisition
The use of radionuclides for scintillation scanning or the use of γ-photography to obtain images of the method, you can diagnose tumors, check the human body organs and study their physiological and biochemical functions and metabolic status, access to dynamic information. For example, 201Tl used for myocardial examination, early detection of coronary heart disease and myocardial infarction localization is the most sensitive means of examination. And the vast majority of these radionuclides are also produced by the gas pedal. The use of gas pedal sterilization of medical instruments, disposable medical articles, vaccines, antibiotics, proprietary Chinese medicines, etc. is a promising direction for the application of gas pedal in health care. With the previous introduction of the gas pedal in the food insecticide, sterilization of the same reason, can replace the application of high temperature disinfection, chemical disinfection and other methods. However, the radiation dose required for sterilization is greater than the dose required for insecticide.
Particle gas pedal (particle accelerator) is an artificial method to generate high-speed charged particles of the device. Particle gas pedals are commonly used in everyday life, such as cathode ray tubes for television and X-ray tubes. It is an important tool for exploring the nature, internal structure and interactions of atomic nuclei and particles, and has important and wide practical applications in industrial and agricultural production, health care, science and technology. Since E. Rutherford in 1919 with natural radioactive elements radiated a ray bombardment of nitrogen atoms for the first time to achieve the artificial transformation of the elements, physicists have recognized that in order to understand the atomic nucleus, high-speed particles must be used to change the atomic nucleus. Natural radioactivity provides particles with limited energy, only a few megaelectron volts (MeV), the energy of particles in natural cosmic rays is very high, but the particle stream is extremely weak, for example, the energy of 10 ^ 14 electron volts (eV) of particles per hour in the 1 square meter of the area of the average descent of only one, and can not dictate the type, number and energy of particles in the cosmic rays, it is difficult to carry out the work of research. Therefore, in order to carry out experimental research with a desired goal, a variety of particle gas pedals have been developed and constructed over the decades, with ever-increasing performance. In life, television and X-ray facilities, etc. are small particle gas pedals.
Application of particle gas pedal discovered the vast majority of new transuranic elements and synthesized thousands of new artificial radionuclides, and systematic and in-depth study of the basic structure of the atomic nucleus and its law of change, prompting the rapid development of atomic nuclear physics to mature, so as to establish particle physics. In the past 20 years, the application of gas pedal has far exceeded the field of atomic nuclear physics and particle physics, in such as materials science, surface physics, molecular biology, photochemistry and other fields of science and technology have important applications. Gas pedals are widely used in various fields of industry, agriculture and medicine, such as isotope production, tumor diagnosis and treatment, ray disinfection, nondestructive flaw detection, polymer irradiation polymerization, material irradiation modification, ion implantation, ion beam microanalysis, and space radiation simulation, nuclear explosion simulation and so on. To date, thousands of particle gas pedals have been built around the world, a small part of which is used for basic research in atomic nuclear and particle physics, they continue to improve the energy and improve the quality of the beam in the direction of development; the vast majority of the rest belong to the application of particle ray technology based on the "small" type of gas pedal.