Neutronic performances of the MEGAPIE target

TL;DR

This paper characterizes the neutron flux inside the MEGAPIE liquid lead-bismuth spallation target using a specialized detector, providing valuable data for neutron source applications and validating transport models.

Contribution

It introduces a complex micro fission-chamber detector for in-situ neutron flux measurement within the MEGAPIE target, offering detailed spatial and temporal neutron data.

Findings

Neutron flux distribution was successfully measured inside the target.

Temporal variations of neutron flux correlate with beam intensity.

Data constrains neutron production models in transport codes.

Abstract

The MEGAPIE project is a key experiment on the road to Accelerator Driven Systems and it provides the scientific community with unique data on the behavior of a liquid lead-bismuth spallation target under realistic and long term irradiation conditions. The neutronic of such target is of course of prime importance when considering its final destination as an intense neutron source. This is the motivation to characterize the inside neutron flux of the target in operation. A complex detector, made of 8 micro fission-chambers, has been built and installed in the core of the target, few tens of centimeters from the proton/Pb-Bi interaction zone. This detector is designed to measure the absolute neutron flux inside the target, to give its spatial distribution and to correlate its temporal variations with the beam intensity. Moreover, integral information on the neutron energy distribution as a function of the position along the beam axis could be extracted, giving integral constraints on the neutron production models implemented in transport codes such as MCNPX.