Development of a CsI:Tl calorimeter subsystem for the All-Sky Medium-Energy Gamma-Ray Observatory (AMEGO)

Abstract

Abstract-We report on the development of the thallium-doped cesium iodide (CsI:Tl) calorimeter subsystem for the All-Sky Medium-Energy Gamma-ray Observatory (AMEGO) [1]. The CsI:Tl calorimeter is one of the three main subsystems that comprise the AMEGO instrument suite; the others include the double-sided silicon strip detector (DSSD) tracker/converter and a cadmium zinc telluride (CZT) calorimeter. Similar to the LAT instrument on Fermi Gamma-ray Space Telescope, the hodoscopic calorimeter consists of orthogonally layered CsI:Tl bars. Unlike the LAT, which uses PIN photodiodes, the scintillation light from each end of the CsI:Tl bar is read out with recently developed large-area silicon photomultiplier (SiPM) arrays. Development of the calorimeter technology for a large space-based γ-ray observatory is being done via funding from the NASA APRA program. Under this program, we have designed, built and are currently testing a prototype consisting of 24 CsI:Tl bars (each with dimensions of 16.7 mm x 16.7 mm x 100 mm) hodoscopically arranged in four layers with six bars per layer. The ends of each bar are read out with SensL ArrayJ quad SiPMs. Signal readout and processing is done with the IDEAS SIPHRA (IDE3380) ASIC. Performance testing of this prototype was done with laboratory sources and at an initial beam test; future testing and characterization will be done during a second beam test (2019) and a balloon flight (2020) in conjunction with the other subsystems led by NASA-GSFC. We will discuss the initial calibration tests, construction of the prototypes and the most up-to-date results from laboratory and beam tests with analog/digital electronics and the SIPHRA DAQ.

AMEGO: Exploring the Extreme Multimessenger Universe

“…The SiPM signals are processed with IDEAS VA32TA6 ASICs located on the FEE boards at the perimeter of the layer, and the corner of each layer contains a digital backend board with an FPGA that controls the ASICs for a single layer and communication with the rest of the instrument With the use of the SiPM readout, the AMEGO calorimeter has significant improvement over Fermi-LAT at low energies with a threshold of 60 keV, compared to 600 keV for the Fermi-LAT PIN diode readout. 20 The CsI High Energy Calorimeter has been modeled off of the Fermi-LAT calorimeter and is being designed and built by the same team at the Naval Research Laboratory (NRL). The Fermi-LAT has given hodoscopic arrays of CsI scintillating bars flight heritage.…”

Subsystem Development for the All-Sky Medium Energy Gamma-ray Observatory (AMEGO) prototype

“…The bar is then wrapped in a diffuse reflective material (Tetratex) in order to maximise light collection and 6 mm × 6 mm SiPM arrays are bonded to the end of each scintillator bar. A photo of the prototype hodoscope is given in Figure 4 and more details can be found in [10]. For full AMEGO, the CsI bars will be closer to ∼ 40 cm, commensurate with the footprint of a full tower.…”

Development of the ComPair gamma-ray telescope prototype

“…The crystals are then wrapped with Tetratex to increase light output. 22 Each end of the bar is read out by a 2 × 2 array of 6 × 6 mm 2 J-series SiPMs manufactured by ON Semiconductors. Fig.…”