Measurements of Fission Products Yields with the LOHENGRIN mass spectrometer at ILL

A Chebboubi,M Ramdhane,A Letourneau,D Bernard,O Serot,O Litaize,Y.H Kim,H Faust,M Rapala,S Julien-Laferrière,P Mutti,J Nicholson,C Sage,A Blanc,U Köster,O Méplan,G Kessedjian

doi:10.1051/epjconf/202024201001

Abstract

The CEA in collaboration with ILL and LPSC has developed a measurement program on symmetric and heavy mass fission product distributions. The combination of measurements with ionisation chamber and Ge detectors is necessary to describe precisely the heavy fission product region in mass and charge. Recently, new measurements of fission yields and kinetic energy distributions, for different fissioning systems (233,235 U(nth, f),241 Am(2nth, f) and 239,241 Pu(nth, f), were performed with recoil spectrometer LOHENGRIN. The focus has been done on the self-normalization of the data to provide new absolute measurements, independently of any libraries along with the experimental covariance matrix. To reach precise measurements, a new experimental procedure was developed along with a new analysis method.

Highlights

Introduction235U(nth, f ) [8], 233U(nth, f ) [9] and 241Pu(nth, f ) [10] were measured. In this article, a focus on the mass yield measurements is made
The CEA in collaboration with Institut Laue-Langevin (ILL) and LPSC has developed a measurement program on symmetric and heavy mass fission product distributions
The combination of a magnetic and electric fields allows a separation of the produced fission products according to their ratios mass A over ionic charge q and kinetic energy Ek over ionic charge

Summary

Introduction

235U(nth, f ) [8], 233U(nth, f ) [9] and 241Pu(nth, f ) [10] were measured. In this article, a focus on the mass yield measurements is made. The correction due to the (Ek, q) correlation is performed through the ionic charge distribution This correction is made in order to answer to the following question: what would be the weight of each P(q, Ekm) if the measurement was made at a different kinetic energy? The kinetic energy distribution is assumed Gaussian, which is a good approximation when using a thin target (typically under 100 μg.cm−2) With this new procedure, a relative mass yield can be estimated for different ionic charges q: N(A|q) =. Taking into account the correlation (Ek, q) permits to reduce the uncertainty and the bias introduced by the classical procedure to estimate the fission mass yields on LOHENGRIN In this method, the mass A = 139 is supposed to be completely measured through γ spectroscopy. This example shows how the isotopic yields are sensitive to the nuclear structure parameters

Other observables of interest to study the fission process

Conclusion