Surface Characterization of P-Type Point Contact Germanium Detectors

Edzards, F.; Hauertmann, Lukas; Abt, I.; Gooch, C.; Lehnert, B.; Liu, Xiang; Mertens, S.; Radford, D. C.; Schulz, O.; Willers, M.

doi:10.3390/particles4040036

Cited by 5 publications

(6 citation statements)

References 21 publications

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“…Subsequent measurements of this same detector in the event characterization test-stand described in Ref. [ 27 ] have found opposite behavior from that observed with the TUBE scanner, with the DCR component of events decreasing with increasing event incidence radius. In this case, the DCR parameter can still be used to identify events in the energy range relevant for searches.…”

Section: Discussionmentioning

confidence: 91%

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$$\alpha $$-event characterization and rejection in point-contact HPGe detectors

et al. 2022

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P-type point contact (PPC) HPGe detectors are a leading technology for rare event searches due to their excellent energy resolution, low thresholds, and multi-site event rejection capabilities. We have characterized a PPC detector’s response to $$\alpha $$ α particles incident on the sensitive passivated and p$$^+$$ + surfaces, a previously poorly-understood source of background. The detector studied is identical to those in the MajoranaDemonstrator experiment, a search for neutrinoless double-beta decay ($$0\nu \beta \beta $$ 0 ν β β ) in $$^{76}$$ 76 Ge. $$\alpha $$ α decays on most of the passivated surface exhibit significant energy loss due to charge trapping, with waveforms exhibiting a delayed charge recovery (DCR) signature caused by the slow collection of a fraction of the trapped charge. The DCR is found to be complementary to existing methods of $$\alpha $$ α identification, reliably identifying $$\alpha $$ α background events on the passivated surface of the detector. We demonstrate effective rejection of all surface $$\alpha $$ α events (to within statistical uncertainty) with a loss of only 0.2% of bulk events by combining the DCR discriminator with previously-used methods. The DCR discriminator has been used to reduce the background rate in the $$0\nu \beta \beta $$ 0 ν β β region of interest window by an order of magnitude in the MajoranaDemonstrator and will be used in the upcoming LEGEND-200 experiment.

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Section: Discussionmentioning

confidence: 91%

“…Under different operating conditions, however, negative charge build-up could occur, and these models would be appropriate descriptions of the observed behavior, as discussed in Ref. [ 27 ].…”

Section: Modeling the Event Responsementioning

confidence: 99%

$$\alpha $$-event characterization and rejection in point-contact HPGe detectors

et al. 2022

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“…Several warming-cooling cycles probably changed the surface conditions influencing the amount of charge trapping. These changing surface conditions are likely due to build-up of surface charges in the passivation layer as also observed for a p-type point contact (PPC) detector in the same setup [24]. Surface charges would change the local electric field at the surface: either attracting or repelling charge carriers towards or from the surface.…”

Section: Location Dependence Of Charge Trappingmentioning

confidence: 86%

“…24b. 24 Averaged rise times T 90 10 of events induced by collimated 121.8 keV gammas from 152 Eu entering segment 19 from the side for a segment 19 and b the core before full metalisation, adapted from [14,27]. The ϕ-axes were modified to match the coordinate system cho-sen for this paper.…”

Section: Effect Of Metalisationmentioning

confidence: 99%

Identification and simulation of surface alpha events on passivated surfaces of germanium detectors and the influence of metalisation

et al. 2022

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Events from alpha interactions on the surfaces of germanium detectors are a major contribution to the background in germanium-based searches for neutrinoless double-beta decay. Surface events are subject to charge trapping, affecting their pulse shape and reconstructed energy. A study of alpha events on the passivated end-plate of a segmented true-coaxial n-type high-purity germanium detector is presented. Charge trapping is analysed in detail and an existing pulse-shape analysis technique to identify alpha events is verified with mirror pulses observed in the non-collecting channels of the segmented test detector. The observed radial dependence of charge trapping confirms previous results. A dependence of the probability of charge trapping on the crystal axes is observed for the first time. A first model to describe charge trapping effects within the framework of the simulation software SolidStateDetectors.jl is introduced. The influence of metalisation on events from low-energy gamma interactions close to the passivated surface is also presented.

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“…These are specially e cient in distinguishing localized single-scatter events from multiple-site energy depositions, which are typical for Compton-like scattering backgrounds from cosmic rays and other sources. Combined with the possibility of sub-keV threshold and low noise ratio, this kind of detector is very well suited for rare, low energy searches, and already employed in other CE‹NS and neutrinoless double beta decay initiatives [83].…”

Section: • High-pressure Gaseous Tpc (Ess-xe)mentioning

confidence: 99%

Espalhamento Coerente de Neutrino-Núcleo e Modelos Z\' Leve: Formalismo, Fenomenologia e Projeção de Sensitividade

Ramos¹

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The confirmation of non-zero Neutrino masses defines Neutrino Physics phenomena as test cases of central importance to probe scenarios beyond the Standard Model. In particular, future experiments dedicated to the detection of Coherent Elastic Neutrino-Nucleus Scattering may be powerful tools for constraining light new physics. In this work, we introduce a complete approach in order to quantify predictions and derive sensitivity on light Z' mediators for two proposed experiments: a directional low-pressure Time Projection Chamber detector, ‹BDX-DRIFT, that will utilize neutrinos produced at the Long Baseline Neutrino Facility; and several possible experiments to be installed at the European Spallation Source. We compare the results obtained with existing limits from fixed-target, accelerator, solar neutrino and reactor experiments. Furthermore, we show that these experiments have the potential to test unexplored regions that, in some case, could explain the anomalous magnetic moment of the muon or peculiar spectral features in the cosmic neutrino spectrum observed by IceCube.

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Surface Characterization of P-Type Point Contact Germanium Detectors

Cited by 5 publications

References 21 publications

$$\alpha $$-event characterization and rejection in point-contact HPGe detectors

$$\alpha $$-event characterization and rejection in point-contact HPGe detectors

Identification and simulation of surface alpha events on passivated surfaces of germanium detectors and the influence of metalisation

Espalhamento Coerente de Neutrino-Núcleo e Modelos Z\' Leve: Formalismo, Fenomenologia e Projeção de Sensitividade

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