Development of parallel plate avalanche counters for prompt fission neutron spectrum measurement

Abstract

BackgroundThe prompt fission neutron spectrum (PFNS) is an important nuclear reaction data. Coincident measurement between neutron detectors and parallel plate avalanche counters (PPAC) is widely used to measure the PFNS below the energy of the neutron source, hence most of the non-fission neutrons can be exclude.PurposeThis study aims to develop a PPAC to satisfy the PFNS measurement and performance test.MethodsFirst of all, a ten-cell PPAC was designed with low-pressure flow working gas and individual cell functionality. Then the software named "Garfield" was used to simulate the distributions of electric field of two kind of fission chambers, i.e., wire-electrode chamber and plate-electrode chamber, under the same geometric dimensions and working conditions. Finally, the structure and the performance of the PPAC were introduced in detail, and relevant performance of this PPAC was tested by experiment.ResultsThe full width at half maximum (FWHM) of the time-correlated spectrum between two neighbor cells using a 241Am α source is 620 ps. The FWHM of the time-correlated spectrum between a PPAC cell and a liquid scintillator detector is 880 ps using a 252Cf fission source.ConclusionsThe experiment confirms that the time resolution of the designed PPAC is good enough for high event rate measurements.

Keywords

• ppac
• pfns
• coincident measurement
• neutron spectrum
• time response