The Calibration And Integration Of Large Area Neutron Detector Array System

The ICF (inertial confinement fusion), driven by high-power laser, aimed at researching on advanced laser strategic defense technology and the use of laser technology to develop research and technology operation of ICF, and the research work of ICF has been very important on the national economy, military applications, and exploration of basic subjects.The ultimate objective of ICF is to achieve controllable thermonuclear fusion. Ion temperature and fuel areal density <ρR> are two important parameters, which can be used to diagnose whether fusion reaction occurs in the interior of target pill. Ion temperatures achieved in ICF targets are often determined by measuring the energy spectrum of the primary fusion neutrons, and fuel areal density is determined by measuring the energy spectrum of the secondary fusion neutrons. The secondary neutron yield of the implosions experiments on SG-III prototype is estimated only 10~5～10~6. To get the ion temperature Ti and the fuel density <ρR> under low neutron yield, we need to establish a large area neutron detector array to measure the time-of-flight neutron spectrum.The large area neutron detector array system on the SG-III prototype have 960 channels, the flight distance is 16.67 meters, and 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. 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. According to the requests of the prototype system, a 16 channel electronic system is processed.The result of cosmic ray test shows that the performance of small detector system meets the design requirements. But the in-field test result shows that the too strong pulse produced by X-ray and gamma rays generated in the ICF experiment leads to the saturation of the front-end electronics, it impedes normal circuit operation and measurement of the flight time of neutrons. In this paper, we discuss the improved solution, and the experimental test result shows that the improved circuit successfully achieves the expected requirement.The large area neutron detector array system on the SG-III prototype has 960 channels. The structure of the detector system is very complex, and the consistency requirement among the channels is very high. In this paper, we have probed the calibration of the detector system, and established a database that can amend the measurement scales of time and amplitude.The primary innovation in the thesis is as follows.(1) Focused on the problems of the signal reflection, saturation, overshoot induced by the large X-ray, an improved anti-saturation circuit has been put forward, and we have analyzed the device requirements of the front-end electronics. And base on the requirement of the ICF experiment, we have optimized the Timing Control Module.(2) Preparing for the calibration of the large neutron detectors array system, we have established a database which can use for the debugging of the detector system.(3) Preparing for the test of large dynamic range signals, we have conducted a preliminary study, making the early research for the measurement of neutron spectroscopy.