A Helium Gas-Scintillator Active Target for Photoreaction Measurements

TL;DR

This paper presents a helium gas-scintillator active target designed for precise photoreaction cross section measurements, demonstrating good timing resolution and compatibility with high-flux photon beams, supported by detailed Monte Carlo simulations.

Contribution

Introduction of a multi-cell helium gas-scintillator active target with enhanced timing and flux handling capabilities for photoreaction studies, including detailed simulation and experimental validation.

Findings

Good timing resolution achieved

Effective handling of high-flux photon beams

Monte Carlo simulation accurately models target response

Abstract

A multi-cell He gas-scintillator active target, designed for the measurement of photoreaction cross sections, is described. The target has four main chambers, giving an overall thickness of 0.103 $\mathrm{g/cm^{2}}$ at an operating pressure of 2 MPa. Scintillations are read out by photomultiplier tubes and the addition of small amounts of $\mathrm{N}_{2}$ to the He, to shift the scintillation emission from UV to visible, is discussed. First results of measurements at the MAX IV Laboratory tagged-photon facility show that the target has good timing resolution and can cope well with a high-flux photon beam. The determination of reaction cross sections from target yields relies on a Monte Carlo simulation, which considers scintillation light transport, photodisintegration processes in $^{4}\mathrm{He}$, background photon interactions in target windows and interactions of the reaction-product particles in the gas and target container. The predictions of this simulation are compared to the measured target response.