The Test Of Fission Physics Experimental System Vs The Calibration And Study Of PPAC

In this paper, a fission physics experimental system for measure the neutron spectrum of short-lived and neutron-rich nuclei are described in detail. Using ²⁵²Cf and CAMAC data acquiring system, the experimental system get neutron spectrums of fission fragments ,the mass distributions and the charge distributions of fission fragments through 29 parameters for one fission event recorded by detectors. In the system , the desired impact of the detector's functions can be obtained through test. The performance of parallel plate avalanche counter (PPAC) was measured by ²⁴¹Amα, The test results indicate that the position resolution of the chamber is Ax =Ay = 6 mm and the time resolution of every detection unit is 460ps. In the system, flight time and flight track of fission fragments be measured by MCP-PPAC ,the velocity of the fission fragments can be got. The mass of fission fragments were measured by the method of double velocity. In the whole system, time resolution and position resolution of the time-of-flight spectrometer decide distinguish ability for the fission fragments. Time resolution and position resolution of MCP-PPAC be measured by ²⁴¹Amαsource. Because of PPAC large area, the location of the incident particles will have greater uncertainty. In order to reduce the error of time resolution of location uncertainty, the each detection unit be calibrated for its time spectrum. A large area of two-dimensional PPAC avalanche counter was developed for the system. The detector has a sensitive area of 200 mm×250mm, the detector has a two-step gas amplification process and the position is determined though delay line readout mode. The test result indicate that the time of the detector signal rise time reached about 8ns, the location of the signal rise time reached about 4ns, the position resolution of the chamber isâ–³x =â–³y = 4 mm.