Eur. Phys. J. A (2015) 51: 123
https://doi.org/10.1140/epja/i2015-15123-y

Special Article - Tools for Experiment and Theory

A helium gas scintillator active target for photoreaction measurements

¹ School of Physics & Astronomy, University of Glasgow, G12 8QQ, Glasgow, Scotland, UK
² Department of Physics, University of Lund, Sölvegatan 14, SE-223 62, Lund, Sweden
³ MAX IV Laboratory, PO Box 118, SE-221 00, Lund, Sweden
⁴ Fen-Edebiyat Faculty, Süleyman Demirel University, 32 260, Isparta, Turkey
⁵ Kepler Centre for Astro and Particle Physics, Physikalisches Institut, Universität Tübingen, D-72076, Tübingen, Germany

^* e-mail: john.annand@glasgow.ac.uk

Received: 10 July 2015
Revised: 25 August 2015
Accepted: 7 September 2015
Published online: 1 October 2015

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 g/cm³ at an operating pressure of 2 MPa. Scintillations are read out by photomultiplier tubes and the addition of small amounts of N₂ 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 a timing resolution of around 1 ns 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 ⁴He, 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.