Silicon detectors for γ-ray and β-spectroscopy

Litovchenko, P.G.; Wahl, W.; Bisello, D.; Rando, R.; Litovchenko, A.; Lastovetsky, V.F.; Barabash, L.I.; Kibkalo, T.I.; Polivtsev, L.A.; Kolevatov, J. I.; Semenov, V. E.; Trykov, L.A.; Wyss, J.

doi:10.1016/s0168-9002(03)01919-3

Cited by 5 publications

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“…Several studies have reported that uniformly drifting Li ions into a thick, large-area, p-type Si wafer is difficult mainly due to defects and contaminants, such as oxygen and carbon, in the Si crystal [20][21][22][23][32][33][34]. These behave as traps for Li ions and hence decrease Li ion mobility in the crystal, making it hard to uniformly drift.…”

Section: Procurement Of P-type Si Crystalmentioning

confidence: 99%

Developing a mass-production model of large-area Si(Li) detectors with high operating temperatures

Kozai

Fuke

Yamada

et al. 2019

Nuclear Instruments and Methods in Physics Research Section A:

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This study presents a fabrication process for lithium-drifted silicon (Si(Li)) detectors that, compared to previous methods, allows for mass production at a higher yield, while providing a large sensitive area and low leakage currents at relatively high temperatures. This design, developed for the unique requirements of the General Antiparticle Spectrometer (GAPS) experiment, has an overall diameter of 10 cm, with ∼9 cm of active area segmented into 8 readout strips, and an overall thickness of 2.5 mm, with 2.2 mm ( 90%) sensitive thickness. An energy resolution 4 keV full-width at half-maximum (FWHM) for 20−100 keV X-rays is required at the operating temperature ∼ − 40 • C, which is far above the liquid nitrogen temperatures conventionally used to achieve fine energy resolution. High-yield production is also required for GAPS, which consists of 1000 detectors. Our specially-developed Si crystal and custom methods of Li evaporation, diffusion and drifting allow for a thick, large-area and uniform sensitive layer. We find that retaining a thin undrifted layer on the p-side of the detector drastically reduces the leakage current, which is a dominant component of the energy resolution at these temperatures. A guard-ring structure and optimal etching of the detec- tor surface are also confirmed to suppress the leakage current. We report on the mass production of these detectors that is ongoing now, and demonstrate it is capable of delivering a high yield of ∼90%.We present here a high-yield mass production process for lithium-drifted silicon (Si(Li)) detectors that meet the unique requirements of the General Antiparticle Spectrometer (GAPS) experiment. GAPS is a balloon-borne experiment that aims to survey low-energy (<0.25 GeV/n) cosmic-ray antinuclei for the first time, by adopting a novel detection concept based on the physics of exotic atoms [1][2][3][4]. Low-energy cosmic-ray antinuclei, especially antideuterons, are predicted to be distinctive probes for the dark matter annihilation or decay occurring in the Galactic halo [1,[5][6][7][8][9]. Precise measurement of the low-energy antiproton spectra will also provide crucial information on the source and propagation mechanisms of cosmic rays [10][11][12][13]. GAPS sensitivities to antideuterons and antiprotons are discussed in [14] and [13], and capabilities for antihelium detection are being evaluated. The first flight of GAPS via a NASA Antarctic long duration balloon is planned for late 2021.GAPS is comprised of a 1.6 m W × 1.6 m D × 1.0 m H tracker made of Si(Li) detectors surrounded by a time-of-flight (TOF) system made of plastic scintillator paddles. A low-energy antinucleus triggered by the TOF is slowed and captured by the Si(Li) detector array, forming an excited exotic atom with a silicon nucleus. It immediately decays, radiating de-excitation X-rays of characteristic energies. The antinucleus then annihilates with the silicon nucleus, producing pions and protons with a multiplicity that scales with the incident antinucleus mass. The surrounding Si(Li)...

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