Demonstration of surface electron rejection with interleaved germanium detectors for dark matter searches

Agnese, R.; Anderson, A. J.; Balakishiyeva, D.; Thakur, R. Basu; Bauer, D. A.; Borgland, A. W.; Brandt, D.; Brink, P. L.; Bunker, R.; Cabrera, B.; Caldwell, D. O.; Cerdeño, David G.; Chagani, H.; Cherry, M.; Cooley, J.; Cornell, B.; Crewdson, C. H.; Cushman, P.; Daal, M.; Stefano, P. C. F. Di; Silva, E. Do Couto E; Doughty, T.; Esteban, Luis; Fallows, S.; Figueroa‐Feliciano, E.; Fox, J.; Fritts, M.; Godfrey, G.; Golwala, S. R.; Hall, J.; Harris, H. R.; Hasi, J.; Hertel, S. A.; Hines, B. A.; Höfer, T.; Holmgren, D.; Hsu, L.; Huber, M. E.; Jastram, A.; Kamaev, O.; Kara, Burhan; Kelsey, M.; Kenany, S. Al; Kennedy, A.; Kenney, C. J.; Kiveni, M.; Koch, K.; Loer, B.; Asamar, E. Lopez; Mahapatra, R.; Mandic, V.; Martínez, C. Moreno; McCarthy, K. A.; Mirabolfathi, N.; Moffatt, R. A.; Moore, David C.; Nadeau, P.; Nelson, Robert H.; Novák, L.; Page, K.; Partridge, R.; Pepin, M.; Phipps, A.; Prasad, K.; Pyle, M.; Qiu, H.; Radpour, Roxanne; Rau, W.; Redl, P.; Reisetter, A.; Resch, R.; Ricci, Y.; Saab, T.; Sadoulet, B.; Sander, J.; Schmitt, R.; Schneck, K.; Schnee, R. W.; Scorza, S.; Seitz, D. N.; Serfass, B.; Shank, B.; Speller, D.; Tomada, A.; Villano, A. N.; Welliver, B.; Wright, D. H.; Yellin, S.; Yen, J. J.; Young, B. A.; Zhang, J.

doi:10.1063/1.4826093

Cited by 69 publications

(84 citation statements)

References 30 publications

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“…The resulting field structure, along with the sensor layout, provides excellent rejection of surface backgrounds [10]. This ability to reject the vast majority of backgrounds on an event-by-event basis means the iZIP detectors can be operated in a nearly background-free mode.…”

Section: A the Supercdms Detectorsmentioning

confidence: 99%

See 1 more Smart Citation

Projected sensitivity of the SuperCDMS SNOLAB experiment

Agnese¹,

Anderson²,

Aramaki³

et al. 2017

Phys. Rev. D

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294

339

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SuperCDMS SNOLAB will be a next-generation experiment aimed at directly detecting low-mass particles (with masses ≤ 10 GeV=c 2 ) that may constitute dark matter by using cryogenic detectors of two types (HV and iZIP) and two target materials (germanium and silicon). The experiment is being designed with an initial sensitivity to nuclear recoil cross sections ∼1 × 10 −43 cm 2 for a dark matter particle mass of * Corresponding author. tsaab@ufl.edu PHYSICAL REVIEW D 95, 082002 (2017) 2470-0010=2017=95(8)=082002 (17) 082002-1 © 2017 American Physical Society 1 GeV=c 2 , and with capacity to continue exploration to both smaller masses and better sensitivities. The phonon sensitivity of the HV detectors will be sufficient to detect nuclear recoils from sub-GeV dark matter. A detailed calibration of the detector response to low-energy recoils will be needed to optimize running conditions of the HV detectors and to interpret their data for dark matter searches. Low-activity shielding, and the depth of SNOLAB, will reduce most backgrounds, but cosmogenically produced 3 H and naturally occurring 32 Si will be present in the detectors at some level. Even if these backgrounds are 10 times higher than expected, the science reach of the HV detectors would be over 3 orders of magnitude beyond current results for a dark matter mass of 1 GeV=c 2 . The iZIP detectors are relatively insensitive to variations in detector response and backgrounds, and will provide better sensitivity for dark matter particles with masses ≳5 GeV=c 2 . The mix of detector types (HV and iZIP), and targets (germanium and silicon), planned for the experiment, as well as flexibility in how the detectors are operated, will allow us to maximize the low-mass reach, and understand the backgrounds that the experiment will encounter. Upgrades to the experiment, perhaps with a variety of ultra-low-background cryogenic detectors, will extend dark matter sensitivity down to the "neutrino floor," where coherent scatters of solar neutrinos become a limiting background.

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Section: A the Supercdms Detectorsmentioning

confidence: 99%

“…As discussed in Ref. [10], interleaving the iZIP phonon and ionization sensors enables discrimination of surface events at the detector faces. Sensor modularity enables fiducialization of the signal to reject surface events incident at the sidewalls [5].…”

Section: B Surface Event Background Sourcesmentioning

confidence: 99%

Projected sensitivity of the SuperCDMS SNOLAB experiment

Agnese¹,

Anderson²,

Aramaki³

et al. 2017

Phys. Rev. D

Self Cite

294

339

View full text Add to dashboard Cite

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“…The LZ rate (black) assumes a 5600 kg fiducial mass, an exposure of 1000 days, a 100% trigger efficiency between 1 and 30 keV nr , and a flat 50% nuclear-recoil selection efficiency. The SuperCDMS Ge rate (blue) assumes 50 kg of germanium operating in standard iZIP mode [31], an exposure of 1000 days, and a 100% trigger efficiency between 0.5 and 100 keV nr , and a flat 60% combined fiducial-volume and nuclear-recoil selection efficiency. The SuperCDMS Si rate (red) assumes 1 kg of silicon and an exposure of 1000 days.…”

Section: B Comparison Of Target Elements For G2 Direct Detection Expmentioning

confidence: 99%

Dark matter effective field theory scattering in direct detection experiments

Schneck¹,

Cabrera²,

Cerdeño³

et al. 2015

Phys. Rev. D

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We examine the consequences of the effective field theory (EFT) of dark matter-nucleon scattering for current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. We demonstrate that spectral differences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. We also discuss the implications of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.PACS numbers: 95.35.+d,95.30.Cq,29.40.Wk

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“…Mitigation of radon daughters on surfaces has also been critical for SuperNEMO [8] Radon-daughter backgrounds are important to the expected low-mass sensitivity of the SuperCDMS SNOLAB experiment, which will use detectors of germanium and silicon to search for dark matter interactions [13]. Although the SuperCDMS Interleaved Z-sensitive Ionization and Phonon (iZIP) detectors provide excellent rejection of surface events above 8 keV [14], at lower energies the rejection is expected to worsen to the point that radon-daughter backgrounds may dominate [13]. The situation is similar for the SuperCDMS high-voltage (HV) detectors, which provide the experiment's lowest energy threshold by amplifying the ionization signal [5,15].…”

Section: Radon Backgrounds For Supercdms Snolabmentioning

confidence: 99%

Radon mitigation for the SuperCDMS SNOLAB dark matter experiment

Street

Bunker

Miller

et al. 2018

AIP Conference Proceedings

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Abstract. A potential background for the SuperCDMS SNOLAB dark matter experiment is from radon daughters that have plated out onto detector surfaces. To reach desired backgrounds, understanding plate-out rates during detector fabrication as well as mitigating radon in surrounding air is critical. A radon mitigated cleanroom planned at SNOLAB builds upon a system commissioned at the South Dakota School of Mines & Technology (SD Mines). The ultra-low radon cleanroom at SD Mines has air supplied by a vacuum-swing-adsorption radon mitigation system that has achieved >1000× reduction for a cleanroom activity consistent with zero and <0.067 Bq m −3 at 90% confidence. Our simulation of this system, validated against calibration data, provides opportunity for increased understanding and optimization for this and future systems. RADON BACKGROUNDS FOR SUPERCDMS SNOLABA potential source of dominant backgrounds for many rare-event searches or screening detectors is from radon daughter plate-out [1,2]. Backgrounds from 210 Pb and the recoiling 206 Pb nucleus from the α decay of 210 Po were the dominant low-energy backgrounds for XMASS [3,4], SuperCDMS Soudan [5], and EDELWEISS [6]. These backgrounds remain the dominant surface backgrounds for EDELWEISS-III [7]. Mitigation of radon daughters on surfaces has also been critical for SuperNEMO [8] Radon-daughter backgrounds are important to the expected low-mass sensitivity of the SuperCDMS SNOLAB experiment, which will use detectors of germanium and silicon to search for dark matter interactions [13]. Although the SuperCDMS Interleaved Z-sensitive Ionization and Phonon (iZIP) detectors provide excellent rejection of surface events above 8 keV [14], at lower energies the rejection is expected to worsen to the point that radon-daughter backgrounds may dominate [13]. The situation is similar for the SuperCDMS high-voltage (HV) detectors, which provide the experiment's lowest energy threshold by amplifying the ionization signal [5,15]. Below energies of ∼0.5 keV, rejection of events on the detector sidewall surface, based on the relative sizes of signals in the detectors' phonon sensors, becomes ineffective, so radon-daughter surface backgrounds are expected to dominate over bulk backgrounds for 210 Pb concentrations 50 nBq cm −2 . Figure 1 shows how the expected sensitivity of SuperCDMS SNOLAB varies for different surface concentrations of 210 Pb.Without mitigation, radon daughter plate-out during assembly underground at SNOLAB could dominate the expected background. The duration of the SNOLAB assembly is estimated at about 150 hours. At the average SNOLAB radon concentration of 130 Bq m −3 , the expected plate-out would be about 70 nBq cm −2 of 210 Pb. To make this plateout rate negligible, SuperCDMS SNOLAB has a goal of achieving a radon concentration underground of <0.1 Bq m −3 in its assembly cleanroom underground.

show abstract

Demonstration of surface electron rejection with interleaved germanium detectors for dark matter searches

Cited by 69 publications

References 30 publications

Projected sensitivity of the SuperCDMS SNOLAB experiment

Projected sensitivity of the SuperCDMS SNOLAB experiment

Dark matter effective field theory scattering in direct detection experiments

Radon mitigation for the SuperCDMS SNOLAB dark matter experiment

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