Balloon flight test of a Compton telescope based on scintillators with silicon photomultiplier readouts

Abstract

We present the results of the first high-altitude balloon flight test of a concept for an advanced Compton telescope making use of modern scintillator materials with silicon photomultiplier (SiPM) readouts. There is a need in the fields of high-energy astronomy and solar physics for new medium-energy gamma-ray (~0.4 -10 MeV) detectors capable of making sensitive observations of both line and continuum sources over a wide dynamic range. A fast scintillatorbased Compton telescope with SiPM readouts is a promising solution to this instrumentation challenge, since the fast response of the scintillators permits both the rejection of background via time-of-flight (ToF) discrimination and the ability to operate at high count rates. The Solar Compton Telescope (SolCompT) prototype presented here was designed to demonstrate stable performance of this technology under balloon-flight conditions. The SolCompT instrument was a simple two-element Compton telescope, consisting of an approximately one-inch cylindrical stilbene crystal for a scattering detector and a one-inch cubic LaBr 3 :Ce crystal for a calorimeter detector. Both scintillator detectors were read out by 2 × 2 arrays of Hamamatsu S11828-3344 MPPC devices. Custom front-end electronics provided optimum signal rise time and linearity, and custom power supplies automatically adjusted the SiPM bias voltage to compensate for temperature-induced gain variations. A tagged calibration source, consisting of ~240 nCi of 60 Co embedded in plastic scintillator, was placed in the field of view and provided a known source of gamma rays to measure in flight. The SolCompT balloon payload was launched on 24 August 2014 from Fort Sumner, NM, and spent ~3.75 hours at a float altitude of ~123,000 feet. The instrument performed well throughout the flight. After correcting for small (~10%) residual gain variations, we measured an in-flight ToF resolution of ~760 ps (FWHM). Advanced scintillators with SiPM readouts continue to show great promise for future gamma-ray instruments.

A Compton polarimeter using scintillators read out with MPPCs through Citiroc ASIC

“…We are able to make a clear detection of the modulated counting rate for a polarised beam. These results therefore represent an important step forward compared to previous related work [11,19,20].…”

The e-ASTROGAM mission

“…• A 3D-imaging Calorimeter to absorb and measure the energy of the secondary particles; it is made of an array of small scintillation crystals (33,856 CsI (Tl) bars of 5×5×80 mm 3 ) read out by silicon drift photodetectors to achieve the required energy resolution (4.5% at 662 keV);…”

“…Low-power ASICs suitable for the readout of the were already qualified and used on ASTRO-H/HXI [100]. The low-power SiPM sensors selected for the ACD and the solid-state detectors foreseen for the CsI calorimeter have not yet flown on satellite missions but are in use in suborbital prototypes [33] and are planned for use on future space-borne platforms.…”

On the performance of large monolithic LaCl3(Ce) crystals coupled to pixelated silicon photosensors

“…In terms of position and energy response, several recent experimental studies have reported promising results for lanthanum halide crystals coupled to silicon photomultipliers (SiPMs). In particular, Compton devices developed for gamma-ray astronomy such as ASCOT [15], targeting a similar energy range as the one involved in neutron capture reactions (0.5-10 MeV), have found energy resolutions of 5.3% FWHM at 662 keV using a cubic 26´26´26 mm 3 LaBr 3 crystal coupled to an 8x8 pixel SiPM array [16]. In [17] a resolution of 4% FWHM was found for a 28´28´20 mm 3 LaBr 3 crystal with 8´8 pixel SiPM readout.…”