Surface Characterization of P-Type Point Contact Germanium Detectors

Frank Edzards; Lukas Hauertmann; Iris Abt; Chris Gooch; Björn Lehnert; Xiang Liu; Susanne Mertens; David C. Radford; Oliver Schulz; Michael Willers

doi:10.3390/particles4040036

Surface Characterization of P-Type Point Contact Germanium Detectors

Frank Edzards, Lukas Hauertmann, Iris Abt, Chris Gooch, Björn Lehnert, Xiang Liu, Susanne Mertens, David C. Radford, Oliver Schulz, Michael Willers

Physics Division

Research output: Contribution to journal › Article › peer-review

3 Scopus citations

Abstract

P-type point contact (PPC) germanium detectors are used in rare event and low-background searches, including neutrinoless double beta (0νββ) decay, low-energy nuclear recoils, and coherent elastic neutrino-nucleus scattering. The detectors feature an excellent energy resolution, low detection thresholds down to the sub-keV range, and enhanced background rejection capabilities. However, due to their large passivated surface, separating the signal readout contact from the bias voltage electrode, PPC detectors are susceptible to surface effects such as charge build-up. A profound understanding of their response to surface events is essential. In this work, the response of a PPC detector to alpha and beta particles hitting the passivated surface was investigated in a multi-purpose scanning test stand. It is shown that the passivated surface can accumulate charges resulting in a radial-dependent degradation of the observed event energy. In addition, it is demonstrated that the pulse shapes of surface alpha events show characteristic features which can be used to discriminate against these events.

Original language	English
Pages (from-to)	489-511
Number of pages	23
Journal	Particles
Volume	4
Issue number	4
DOIs	https://doi.org/10.3390/particles4040036
State	Published - Dec 2021

Funding

This work was supported by the Max Planck Society and the Technical University of Munich. F. Edzards gratefully acknowledges support by the German Academic Scholarship Foundation (Studienstiftung des deutschen Volkes), and S. Mertens gratefully acknowledges support by the MPRG at TUM program. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Award Numbers DE-FG02-97ER41041, DE-FG02-97ER41033, DE-AC05-00OR22725, as well as Federal Prime Agreement DE-AC02-05CH11231. This material is based upon work supported by the National Science Foundation under Grant No. NSF OISE 1743790 and 1812409.

Funders	Funder number
German Academic Scholarship Foundation
National Science Foundation	1812409, NSF OISE 1743790
U.S. Department of Energy
Office of Science
Nuclear Physics	DE-AC05-00OR22725, DE-AC02-05CH11231, DE-FG02-97ER41033, DE-FG02-97ER41041
Max-Planck-Gesellschaft
Studienstiftung des Deutschen Volkes
Technische Universität München

Keywords

P-type point contact germanium detectors
alpha and beta surface backgrounds
neutrinoless double beta decay

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10.3390/particles4040036

Cite this

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title = "Surface Characterization of P-Type Point Contact Germanium Detectors",

abstract = "P-type point contact (PPC) germanium detectors are used in rare event and low-background searches, including neutrinoless double beta (0νββ) decay, low-energy nuclear recoils, and coherent elastic neutrino-nucleus scattering. The detectors feature an excellent energy resolution, low detection thresholds down to the sub-keV range, and enhanced background rejection capabilities. However, due to their large passivated surface, separating the signal readout contact from the bias voltage electrode, PPC detectors are susceptible to surface effects such as charge build-up. A profound understanding of their response to surface events is essential. In this work, the response of a PPC detector to alpha and beta particles hitting the passivated surface was investigated in a multi-purpose scanning test stand. It is shown that the passivated surface can accumulate charges resulting in a radial-dependent degradation of the observed event energy. In addition, it is demonstrated that the pulse shapes of surface alpha events show characteristic features which can be used to discriminate against these events.",

keywords = "P-type point contact germanium detectors, alpha and beta surface backgrounds, neutrinoless double beta decay",

author = "Frank Edzards and Lukas Hauertmann and Iris Abt and Chris Gooch and Bj{\"o}rn Lehnert and Xiang Liu and Susanne Mertens and Radford, {David C.} and Oliver Schulz and Michael Willers",

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year = "2021",

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AU - Edzards, Frank

AU - Hauertmann, Lukas

AU - Abt, Iris

AU - Gooch, Chris

AU - Lehnert, Björn

AU - Liu, Xiang

AU - Mertens, Susanne

AU - Radford, David C.

AU - Schulz, Oliver

AU - Willers, Michael

PY - 2021/12

Y1 - 2021/12

N2 - P-type point contact (PPC) germanium detectors are used in rare event and low-background searches, including neutrinoless double beta (0νββ) decay, low-energy nuclear recoils, and coherent elastic neutrino-nucleus scattering. The detectors feature an excellent energy resolution, low detection thresholds down to the sub-keV range, and enhanced background rejection capabilities. However, due to their large passivated surface, separating the signal readout contact from the bias voltage electrode, PPC detectors are susceptible to surface effects such as charge build-up. A profound understanding of their response to surface events is essential. In this work, the response of a PPC detector to alpha and beta particles hitting the passivated surface was investigated in a multi-purpose scanning test stand. It is shown that the passivated surface can accumulate charges resulting in a radial-dependent degradation of the observed event energy. In addition, it is demonstrated that the pulse shapes of surface alpha events show characteristic features which can be used to discriminate against these events.

AB - P-type point contact (PPC) germanium detectors are used in rare event and low-background searches, including neutrinoless double beta (0νββ) decay, low-energy nuclear recoils, and coherent elastic neutrino-nucleus scattering. The detectors feature an excellent energy resolution, low detection thresholds down to the sub-keV range, and enhanced background rejection capabilities. However, due to their large passivated surface, separating the signal readout contact from the bias voltage electrode, PPC detectors are susceptible to surface effects such as charge build-up. A profound understanding of their response to surface events is essential. In this work, the response of a PPC detector to alpha and beta particles hitting the passivated surface was investigated in a multi-purpose scanning test stand. It is shown that the passivated surface can accumulate charges resulting in a radial-dependent degradation of the observed event energy. In addition, it is demonstrated that the pulse shapes of surface alpha events show characteristic features which can be used to discriminate against these events.

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Surface Characterization of P-Type Point Contact Germanium Detectors

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