The μTPC method: improving the position resolution of neutron detectors based on MPGDs

D Pfeiffer,E Oliveri,E Oksanen,G Iakovidis,J Birch,R Hall-Wilton,C Höglund,L Ropelewski,L Hultman,F Resnati,P Thuiner

doi:10.1088/1748-0221/10/04/p04004

Abstract

Due to the 3He crisis, alternatives to the standard neutron detection techniques are becoming urgent. In addition, the instruments of the European Spallation Source (ESS) require advances in the state of the art of neutron detection. The instruments need detectors with excellent neutron detection efficiency, high rate capabilities and unprecedented spatial resolution. The Macromolecular Crystallography instrument (NMX) requires a position resolution in the order of 200 μm over a wide angular range of incoming neutrons. Solid converters in combination with Micro Pattern Gaseous Detectors (MPGDs) are proposed to meet the new requirements. Charged particles rising from the neutron capture have usually ranges larger than several millimetres in gas. This is apparently in contrast with the requirements for the position resolution. In this paper, we present an analysis technique, new in the field of neutron detection, based on the Time Projection Chamber (TPC) concept. Using a standard Single-GEM with the cathode coated with 10B4C, we extract the neutron interaction point with a resolution of better than σ = 200 μm.

Highlights

The α particle has an energy of Ekin
The μTPC concept has been developed by the ATLAS collaboration and is used in particle physics [20, 21]
2.2 Single-GEM detector setup A 300 μm thick aluminium sheet coated with 1 μm of 10B4C [13] was used as neutron converter and detector cathode of the Single-GEM

Summary

Experimental setups

The detectors used for the measurements were one standard 10 x 10 cm Triple-GEM [22] and one 10 x 10 cm Single-GEM detector. A solid layer of 10B4C of 1 μm thickness sputtered onto a 25 μm thick aluminium foil [13, 23] was used as neutron converter. It covered only half of the active area of the detector, and was kept at the same potential as the standard detector cathode installed above. For the measurements with the Single-GEM a gain of 40 was used in combination with a drift gap of 8 mm and a drift field of 1 kV/cm. Low drift velocities assure the ability to distinguish the inclination of the α particle and 7Li ion tracks, allowing their three-dimensional reconstruction

Detector readout and DAQ

TPC analysis

Findings

Conclusions