Multi-parameter Measurement System Of Fission Properties

Fission fragments are the important products in the fission processes. The kinetic distributions, mass distributions and charge distributions of the fragments are the important properties of the fission processes, researches on the attributes of them and correlations between them can provide information for nuclear dynamic theories and data information for fission application. The work of this thesis concentrates on the establishment and test of the multi-parameter fission measurement system in China Institute of Atomic Energy, which can measure the correlations between the fragment mass, fragment charge and fission neutrons.In this measurement system, fragment mass distributions are measured with double velocity method, fragment charge distributions are measured through K-X rays, and neutron spectra are measured using time of flight method, Data acquisition system, which is based on CAMAC-bus using Kmax finishes the correlation measurement and records the data event by event on the computer disk. The two fission fragments are emitted in the opposite direction after fission, and neutrons emitted by a given fragment have a tendency to be in the fragment direction. So the fragment detectors and neutron detectors are placed on the opposite sides of the Cf source. A carbon foil is mounted in one fragment direction, through which fragments pass, secondary electrons are generated, then accelerated and deflected by 90 degree onto MCP using an electrostatic mirror formed by parallel grids. MCP anode signals, which are derived by amplifying the secondary electron signals, indicate fission occur and are used as the start signals of time of flight of the neutrons and fragments. Scintillation detector signals and PPAC detector signals are used as the stop signals of neutron and fragment time of flight, separately. There are no correlations between K-X rays with fragments motion, so HPGe detectors was placed in the direction perpendicular to the fragment detector direction. The ²⁵²Cf source which was prepared by vacuum self-transfer onto a thin carbon film was designed to form the same angles with the detectors. The coincidence of PPAC signals triggers the data acquisition system.In this paper, measurement principles and methods of the fission multi-parameter system are described in detail. And how to debug the system is also included. In order to solve the interference of instant neutrons emitted by complementary fragment during the measurement for the fragment of given A. Neutron spectra in the parallel directions and opposite direction to the fragment direction were calculated using the Monte Carlo method, which helps the uncertainty analysis and modification of the neutron spectra.The detectors properties used in the system can meet the physical demand to measure the fission fragment basically. The system can be used to measure the fragment mass distributions, charge distributions and neutron energy spectra, furthermore, it can be widely used in the field of fission researches.