ALOFT Gamma-ray Detectors
Overview of the UIB-BGO and iSTORM gamma-ray detectors.
University of Bergen: Bismuth-Germanite detector (UIB-BGO)
The gamma-ray instruments have been modified to accommodate the wide dynamic range required between the modest gamma-ray glow flux and the extremely high peak fluxes in TGFs. In addition, UIB-BGO will be able to provide real time telemetry of gamma-ray observations, enabling detection of glows and subsequent re-flight of glowing thunderstorms within minutes of their observation. This package includes 4 different gamma-ray detectors, optimized to cover 4 orders of magnitude dynamic range.
BGO/PMT detector*
Size: 15 x 15 x 3.2 cm3
Time resolution: 0.5 us
Energy range: 300 keV – 40 MeV
LYSO/SiPM detector
Size: 5 x 5 x 5 cm3
Time resolution: 0.1 us
Energy range: 300 keV – 40 MeV
LYSO/SiPM detector
Size: 1 x 1 x 1 cm3
Time resolution: 0.1 us
Energy range: > 300 keV - counter
LYSO/SiPM detector
Size: 0.3 x 0.3 x 1 cm3
Time resolution: 0.1 us
Energy range: > 300 keV - counter
* From BGO/PMT (Photomultiplier Tube) we will receive real-time 1 second resolution data to identify gamma-ray glows and instruct the pilot to return to the cell
PI: Nikolai Østgaard
Team: Martino Marisaldi, Kjetil Ullaland, Shiming Yang, Bilal Qureshi, Jens Søndergaard, Bendik Husa
References
N. Østgaard , H. J. Christian, J. E. Grove, D. Sarria, A. Mezentsev, P. Kochkin, N. Lehtinen, M. Quick, S. Al-Nussirat, E. Wulf, G. Genov, K. Ullaland, M. Marisaldi, S. Yang, R. J., Blakeslee Gamma-ray glow observations at 20 km altitude, J. Geophys. Res., doi: 10.1029/2019JD030312, June 2019
P. Kochkin, N. Østgaard, H. J. Christian,, J. E. Grove, M. Quick, S. Al-Nussirat, E. Wulf, S. Yang , G. Genov, K. Ullaland, M. Marisaldi, N. Lehtinen, A. Mezentsev, D. Sarria, A rapid Gamma-Ray Glow flux reduction observed from 20 km altitude, J. Geophys. Res., doi: 10.1029/2020JD033467, April 2021
iSTORM
The in-Situ Thunderstorm Observer for Radiation Mechanisms, iSTORM, is a gamma-ray spectrometer optimized to make sensitive measurements of bright, fast transients in the nuclear gamma-ray band (~100 keV to >5 MeV). Designed and built by the US Naval Research Laboratory, iSTORM is a highly-segmented array of fast, high-resolution inorganic scintillators. The large total area provides high sensitivity, while the high segmentation and fast scintillation decay time preserves that large area for bright TGFs, which would paralyze a single detector of equal area. The high spectral resolution enables sensitive searches for 511 keV emission from annihilation of secondary positrons created in Terrestrial Electron Beams (TEBs) and the 2.2 MeV line from capture of secondary neutrons from intense TGFs.
CeBr3 / SiPM detector
Quantity: 32
Size: 2.5Ø x 2.5 cm3
Time resolution: <1 us
Energy range: ~100 keV – 5 MeV
Plastic / SiPM detector
Quantity: 1
Size: 1 x 1 x 1 cm3
Time resolution: <1 us
Energy range: >100 keV
SiPM array detector
Quantity: 1
Size: 2.5Ø cm
Time resolution: <1 us
Energy range: n/a
iSTORM comprises an array of 32 CeBr3 scintillators, each 25 mm diameter by 25 mm length, and one 25 mm x 25 mm x 25 mm plastic scintillator cube. Each scintillator is read out by a custom array of silicon photomultipliers (SiPMs), which provide low-noise, high-gain amplification in a compact, low-voltage package. One additional bare SiPM array in a dark box tests for radio-frequency pickup in the instrument electronics.
Signals from each SiPM array are digitized by a commercial front-end board with ASICs that provide dual-gain preamplifiers, shaping, and peak-detect circuitry appropriate for fast scintillators with SiPM readout. A GPS receiver enables precise time-tagging of individual photons. Thermostatically controlled heaters provide thermal control, and instrument temperatures are logged by an array of thermistors.
iSTORM stores the time-tagged event-list data and housekeeping information for post-flight downloading and analysis. The instrument will fly on a NASA ER-2 research aircraft over Central America and the Caribbean at 20 km altitude as part of ALOFT mission.
Work on iSTORM at NRL is supported by ONR 6.1 Base Program funds.