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/cm2 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 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 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.
@article{arxiv.1503.05545,
title = {A Helium Gas-Scintillator Active Target for Photoreaction Measurements},
author = {R. Al Jebali and J. R. M. Annand and J. -O. Adler and I. Akkurt and E. Buchanan and J. Brudvik and K. Fissum and S. Gardner and D. J. Hamilton and K. Hansen and L. Isaksson and K. Livingston and M. Lundin and J. C. McGeorge and I. J. D. MacGregor and R. MacRae and D. G. Middleton and A. J. H. Reiter and G. Rosner and B. Schröder and J. Sjögren and D. Sokhan and B. Strandberg},
journal= {arXiv preprint arXiv:1503.05545},
year = {2015}
}