Tests of ionization chambers for future photofission experiments

Marius Peck,Joachim Enders,Martin Freudenberger,Andreas Oberstedt,Alf Göök,Stephan Oberstedt

doi:10.1051/epjconf/201819304006

Abstract

A recent set-up of a multi-cathode Frisch-grid ionization chamber and experimental results of a proof-of-principle experiment are presented. Preliminary data on the obtained polar angular and mass distributions as well as total kinetic energy of fission fragments produced in neutron-induced fission of 232Th and 238U are discussed that show that the chamber has been operated successfully. For the additional measurement of the azimuthal angular distribution, a design of segmented anodes has been tested. Preliminary data do not allow a suffcient reconstruction of the azimuthal angle.

Highlights

Photofission in the barrier region suffers from relatively low cross sections [1]
Besides using intense bremsstrahlung at the Superconducting-DArmstadt LINear ACcelerator (S-DALINAC) [2] or monochromatic γ-ray beams at the future ELI-NP facility [3], significant amounts of target material need to be placed in the beam to reach sufficient luminosity
To avoid this negative effect and yet gain a better experimental luminosity, multiple fission targets may be installed in a multi-cathode chamber inside the beam. This raises the luminosity by a factor identical to the installed targets. Another benefit of studying several targets simultaneously is to measure the properties of the fission fragments detected in each detector segment parallel, thereby, e.g., allowing to calibrate relative energies between the chamber parts

Summary

Introduction

Photofission in the barrier region suffers from relatively low cross sections [1]. besides using intense bremsstrahlung at the Superconducting-DArmstadt LINear ACcelerator (S-DALINAC) [2] or monochromatic γ-ray beams at the future ELI-NP facility [3], significant amounts of target material need to be placed in the beam to reach sufficient luminosity. Influences the extracted experimental results and limits the resolution of the fission-fragment properties [4, 5] To avoid this negative effect and yet gain a better experimental luminosity, multiple fission targets may be installed in a multi-cathode chamber inside the beam. The determination of fission fragment masses was based on the well established double-kinetic-energy (2E) technique, and the fragment polar emission angle was extracted from the drift time of the ionization electrons [8] This quite simple experimental set-up and the excellent results acquired motivated using the design as a blueprint for a multi-cathode Frisch-grid ionization chamber.

Multi-cathode Frisch-grid ionization chamber

Test of segmented anodes

Findings

Conclusion and outlook