Defective fission correlation data from the 2E-2v method

TL;DR

This paper critically examines the $2E$-$2v$ method for measuring fission fragment data, revealing significant biases in neutron multiplicity correlations and proposing a correction technique to improve data accuracy.

Contribution

It identifies fundamental shortcomings in the $2E$-$2v$ method and introduces a correction approach to mitigate biases in fission data analysis.

Findings

The $2E$-$2v$ method causes large deviations in neutron multiplicity correlations.

It exaggerates the 'sawtooth' shape of $ar{ u}(A)$.

A correction method is proposed to improve data accuracy.

Abstract

The double-energy double-velocity ($2E$-$2v$) method allows assessing fission-fragment mass yields prior to and after prompt neutron emission with high resolution. It is, therefore, considered as a complementary technique to assess average prompt neutron multiplicity as a function of fragment properties. We have studied the intrinsic features of the $2E$-$2v$ method by means of event-wise generated fission-fragment data and found severe short-comings in the method itself as well as in some common practice of application. We find that the $2E$-$2v$ method leads to large deviations in the correlation between the prompt neutron multiplicity and pre-neutron mass, which deforms and exaggerates the so called `sawtooth' shape of $\bar{\nu}(A)$. We have identified the treatment of prompt neutron emission from the fragments as the origin of the problem. The intrinsic nature of this deficiency, risk to render $2E$-$2v$ experiments much less interesting. We suggest a method to correct the $2E$-$2v$ data, and recommend applying this method to previous data acquired in $2E$-$2v$ experiments, as well.