Construction of high-resolution energy—time-of-flight spectrometer for determination of fission fragment mass distributions

Purpose With the aim of determining mass yield distributions of primary fission products, a one-arm spectrometer was developed based on kinetic energy and time-of-flight correlation measurement technique.
Methods An axial grid ionization chamber (GIC) was designed for energy detecting. In order to minimize energy losses and straggling, a thin silicon nitride film with a thickness of 100 nm was performed as the entrance window of the GIC. The energy resolution is 0.38% for 80 MeV ⁶³Cu particles. Two-timing detectors based on the detection of secondary emission electrons by microchannel plates (MCPs) constitute the time pick-off system, and the time-of-flight resolution is better than 200 ps (FWHM) measured with a ²⁴¹Am α source. With a flight path length of 47.6 cm, the path length resolution is 0.21%.
Results and conclusion The first result of mass distribution from ²⁵²Cf spontaneous fission was reported. Energy losses of fragments in dead layers of the spectrometer were corrected event-by-event depend on the Monte Carlo calculation. The mass resolution for light fission fragments peak A=107 amu is 1.3 aum.