Icf Experimental Neutron Detector Study

High temperature and high density of thermonuclear ignition is the core issue in ICF research field. According to Lawson criterion, during the laser fusion process, Fuel areal density <ρR>≥0.4g/cm2 when will it be possible to achieve thermonuclear ignition. Therefore, as the ICF study deepens, <ρR> diagnosis has become increasingly important. Non-symmetric two-dimensional implosion will be the main effect of SG-III prototype, under which the neutron yield is very low. Considering the high price and safety of tritium fuel target, either on the international implosion experiments or the implosion experiments on SG-III prototype in the future, the main targets are filled with pure deuterium fuel, under such conditions, the neutron yield is much lower. The secondary neutron yield of the implosions experiments on SG-III prototype is estimated only 10~5-10~6. <ρR> in high compression state can be given by measuring the secondary neutron spectrum of pure deuterium fuel implosion. And, by measuring the secondary neutron energy spectrum, we can analyze various physical processes which can influence the ICF implosion, to understand the various implosion target compression and the combustion of fuels, to optimize the design of various targets and black cavity. To get the ion temperature Ti and the fuel density <ρR> under such low neutron yield, we need to establish a large area neutron detector array to measure the time-of-flight neutron spectrum. Large area neutron detector array system is almost the only means of detection in the world, It has become the technical standards of diagnosis of Ti and <ρR>. The United States, Japan and the United Kingdom are carrying out such technology, and have constructed several detector array systems.The ICF experiments on the SG-III prototype have some requests on the large area neutron detector array system: the secondary DT neutron detection level can be 4×10~5, the neutron energy resolution corresponding to the neutron time-of-flight spectrum can reach 90keV. In response to these requests, with SG-III prototype device field conditions and the reference to foreign ICF Experimental Device large neutron detector array and the design of performance indicators, we can calculate the size of SG-III prototype large area neutron detector array: 960 channels, the flight distance is 16.67 meters, and the DT neutron detection efficiency is about 20%. Meanwhile, the total time resolution of measured time-of-flight spectrum of the large area neutron detector array is required 1.0ns. Among them, overall time resolution of the electronic system is asking 100ps.Since the control, measurement and data acquisition equipment of SG-III prototype are mostly based on the standard VME bus design, In order to achieve good communication between the neutron detector array and ICF experiment data acquisition and processing systems, and to ensure high reliability, strong interoperability and maintainability, Its electronic system will be based on standard 6U VME bus design. The complex electronic system was divided into several measurement modules. Each module only needs to achieve a certain function or several, several connected modules will compose a comprehensive measurement system.The research on the large area neutron detector array, the first is to establish a set of multi-channel neutron detector array prototype. For the principle Exploration of <ρR> diagnosis, In this paper the design of a 16-channel detector and the electronic system prototype is described. Development of a prototype includes the detector development, electronic system design and the consistency matching of the detection system. If the prototype system is designed successfully and tested to find meet the demand. The entire 960 channels of neutron detector array will be composed of duplicated prototype systems.According to the requests of the prototype system, a 16 channel electronic system prototype is designed and processed, including four main components of measurement: Amplifier Timing Discriminator, Shaping Amplifier, ADC and TDC. And the electronic test, debug and correction software of the prototype is also prepared. After the individual test of the each component, the four main components are connected and tested. The test results show that the electronic system can meet the design requirements in the range, consistency, stability and crosstalk. The time resolution of the electronic system can reach 100ps, which can meet the demand either. Furthermore, in order to simulate the real operation of the neutron detector in ICF experiment, using the output signals from two PMT following a large scintillator as the input signals of the electronic system, we test the performance testing for the entire detector and electronic system as a whole, as well as amplitude walk correction for the acquired data. Final results show that the overall time resolution of the neutron detector array prototype is about 225ps which meets the experimental needs. If considered the timing differences of the two PMT output signal bringing on by the size of experimental device, the time resolution can better.The primary innovation in the thesis is as follows.(1) The research on ICF neutron spectroscopy method of measurement is launched, which is the first of its kind in China. Previously China has no related reports of <ρR> diagnosis under high density compression in ICF experiment. And currently foreign research organization are using large area neutron detectors array to measure the secondary neutron energy spectrum, through which <ρR> can be diagnosed. This technology has become <ρR> diagnosis technology standards in ICF experiments. (2) A 16 channel prototype of the neutron time-of-flight measurement system is established. The focus is on the key component of the system—Amplifier Timing Discriminator component. The ultrafast PMT signal read out and matching and fast discrimination of signal are successfully resolved. The amplitude and timing performance both meet the design requirements.(3) In order to test the 16 channel prototype system, a complete test platform is constructed, and the exploration for test methods of detector and electronic system is done either. The test results of the performance of the prototype system are the same as the results using the test platform of ORTEC company.