Performance of STEFF at nTOF EAR2 and the development of its data analysis framework for fission experiments

Abstract

The SpecTrometer for Exotic Fission Fragments (STEFF) has been used to perform a series of experimental campaigns at the neutron time of flight (nTOF) facility at CERN. The analysis of the data collected in the 2016 $^{235}$U experimental campaign has been presented along with suggestions for improvements in the processing of the data collected in the 2018 $^{239}$Pu experimental campaign. Segmented anodes in the Bragg and Bragg Stop detector were studied, with methodologies developed to treat the segments in each detector both individually and collectively as a whole. The analysis of data from the Bragg detector involved a procedure of gain corrections, a study of charge-sharing, and a method of sum signal reconstruction. The analysis of data from the Bragg Stop detector involved a procedure of alignment corrections, a method of primary signal identification, and corrections for variations in flight path. The timing resolution for fission fragments along the Bragg arm of STEFF was found to be 1.76 ns. The above analyses were combined using the Schmitt method to extract the fragment energy and mass distributions at low (sub-eV) neutron energies, yielding a mass resolution of 4.11 amu along the Bragg arm. The capabilities of STEFF to provide nuclear data measurements at nTOF at higher neutron energies was investigated with indications of successful operation extending into the keV-region. The methods of analysis developed using the Bragg arm of STEFF are ready to be extended to the Hips arm of STEFF, and also to the processed data from other STEFF experiments at nTOF.

Date of Award	21 Mar 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Gavin Smith (Main Supervisor) & Tobias Wright (Co Supervisor)