Development And Performance Of CVD Diamond Film Radiation Detectors

With the wide application of nuclear technology,the application environment of nuclear radiation detector becomes more and more rigorous.Radiation protection and the safety and controllability of radiation environment are becoming more and more important.Traditional semiconductor materials such as silicon?Si?,germanium?Ge?,gallium arsenide?GaAs?,silicon carbide?SIC?,gallium nitride?GaN?and other semiconductor nuclear radiation detectors have been difficult to meet the requirements of nuclear fission,nuclear fusion,accelerator,outer space and other high temperature,high radiation environment for safe service,we must find new materials to make a new generation of nuclear radiation detector.Diamond has excellent optical,electrical,thermal,mechanical and radiation resistance properties,and has become the preferred material for making a new generation of radiation detector.The preparation of detector level diamond film,the development of diamond detector and the application of diamond film detector in various radiation environments have become a hot topic in the field of radiation detection technology at home and abroad.Because radiation detection technology often has a direct and close relationship with national defense construction,at present,the core technology of synthetic high-quality diamond and diamond detector is mainly in the hands of a few companies in Austria and the United States.Some high-quality diamond detectors used in china depend on imports.The development of high-quality diamond detectors for high radiation environment and the mastery of independent intellectual property rights are conducive to the localization of core components.This paper briefly describes the concept of nuclear radiation,the detection principle of four kinds of common nuclear radiation,three types of radiation detectors and their main performance indexes,and three advantages of diamond detectors.This paper mainly introduces the research progress of diamond detector at home and abroad.By analyzing the working principle of diamond detector for charged particles and neutrons,the performance index and manufacturing method of diamond detector,it sums up the difficulties and solutions for the preparation of diamond detector.The most outstanding difficulty is that the synthetic diamond film is a defective crystal material,and the quality of the material is difficult to meet the requirements of the ideal performance of the detector.The first solution is to optimize the preparation process parameters to improve the purity of diamond film and reduce the grain boundary defects,so as to meet the requirements of detector.The other is to design and prepare various electrode structures of diamond detector to meet the requirements of various environmental safety service.In this paper,the detector level diamond films were prepared by the optimized electronic assisted chemical vapor deposition?EACVD?.According to the requirements of various service environments,three kinds of diamond film detectors,X-ray,neutron and magnetic pulse,are developed.In the environment of Z-pinch X-ray,fusion neutron radiation,high pulse current and strong magnetic field radiation,a series of detection and experimental evaluation are carried out.In this paper,tantalum hot wire,whose evaporation rate is significantly lower than that of tungsten and whose thermal electron emissivity is nearly one order of magnitude higher than that of tungsten,is used to replace the tungsten hot wire in the original EACVD device,and the distance between the tantalum hot wire array wires is optimized to 4mm,and the area of the uniform plasma of the hot wire is optimized to 60mm×60mm;the cooling channel of the deposition platform in the original EACVD device is optimized to be a circular fine channel to improve the temperature of the diamond film deposition platform.The DC discharge mode in the original EACVD device was optimized as pulse discharge mode,and the arc discharge was restrained to reduce the film impurities formed by hot wire sputtering,and the high-purity diamond film with grain size up to 100?m was prepared.According to the characteristics of X-ray detection in Z-pinch device,the interdigital electrode with interdigital width of 25?m and adjacent interdigital spacing of 25?m is printed on the crystal size of 60mm×60mm×500?m high-purity diamond film,and the X-ray detector is made.The experimental measurement on the Z-pinch strong x-ray device shows that the diamond detector has good robustness and can be applied to high-quality diamond film Energy pulse x-ray detection.In this paper,a diamond neutron detector for deuterium tritium fusion neutron detection has been developed by using a 4.5mm×4.5mm×500?m single crystal diamond film and a sandwich structure formed by a flat gold electrode and a track shaped gold electrode.The results of numerical simulation of electric field distribution show that the electric field near the electrode of the structure is obviously enhanced,and the current intensity collected by the electrode per unit area is also increased twice;under the electric field of 30kV/cm,the measured dark current of the detector is less than 0.1nA;the flux of the D-T fusion neutron source measured by the detector is about 7.5×10⁵/?s.cm²?,and the characteristic peak of the reaction¹²C?n,??⁹Be center of the neutron spectrum is 8.28MeV,and its energy is measured the resolution is better than 1.69%;at the same time,a response characteristic peak¹²C?n,n'?3?with a central energy of 6.52MeV is detected,and its energy resolution is greater than 7.67%.In this paper,the polycrystalline diamond film with a thickness of 20?m was prepared by the optimized EACVD device as the substrate and insulating material,and the differential magnetic probe was developed by two symmetrical differential circuits composed of gold rings with an inner diameter,a width and a thickness of 0.8 mm,50?m and 1?m on the positive and negative surfaces of the diamond film.The actual measurement results of pulsed magnetic field show that the differential magnetic probe has good common mode rejection ratio,ns time resolution and mm spatial resolution.