- Collaboration, The MAJORANA
- Arnquist, IJ
- III, FT Avignone
- Barabash, AS
- Barton, CJ
- Bertrand, FE
- Blalock, E
- Bos, B
- Busch, M
- Buuck, M
- Caldwell, TS
- Chan, Y-D
- Christofferson, CD
- Chu, P-H
- Clark, ML
- Cuesta, C
- Detwiler, JA
- Drobizhev, A
- Edwards, TR
- Edwins, DW
- Efremenko, Yu
- Elliott, SR
- Gilliss, T
- Giovanetti, GK
- Green, MP
- Gruszko, J
- Guinn, IS
- Guiseppe, VE
- Haufe, CR
- Hegedus, RJ
- Henning, R
- Aguilar, D Hervas
- Hoppe, EW
- Hostiuc, A
- Kim, I
- Kouzes, RT
- Lopez, AM
- López-Castaño, JM
- Martin, EL
- Martin, RD
- Massarczyk, R
- Meijer, SJ
- Mertens, S
- Myslik, J
- Oli, TK
- Othman, G
- Pettus, W
- Poon, AWP
- Radford, DC
- Rager, J
- Reine, AL
- Rielage, K
- Ruof, NW
- Saykı, B
- önert, S Sch
- Stortini, MJ
- Tedeschi, D
- Varner, RL
- Vasilyev, S
- Wilkerson, JF
- Willers, M
- Wiseman, C
- Xu, W
- Yu, C-H
- Zhu, BX
- et al.
P-type point contact HPGe detectors are a leading technology for rare event
searches in germanium due to their excellent energy resolution, low thresholds,
and multi-site event rejection capabilities. $\alpha$ particles incident on the
passivated surface of these detectors lead to a previously poorly understood
background. We have characterized a PPC detector's response to $\alpha$
particles incident on the sensitive passivated and p$^+$ surfaces. The detector
studied is identical to those in the MAJORANA DEMONSTRATOR experiment, a search
for neutrinoless double-beta decay ($0\nu\beta\beta$) in $^{76}$Ge. $\alpha$
decays on most of the passivated surface exhibit significant energy loss due to
charge trapping. These waveforms are also distorted, with a delayed charge
signature caused by the slow recovery of a fraction of the trapped charge. This
signature can be used to reliably identify $\alpha$ background events on the
passivated surface of the detector. In this measurement, this method is
complementary to existing rising-edge-based analysis methods of $\alpha$
identification. We demonstrate effective rejection of all surface $\alpha$
events (to within statistical uncertainty) with a loss of only 0.2% of bulk
events by combining the delayed charge recovery (DCR) discriminator with
previously-used methods. The DCR discriminator has been used to reduce the
background rate in the $0\nu\beta\beta$ region of interest window by an order
of magnitude in the MAJORANA DEMONSTRATOR, and is planned for use in the
upcoming LEGEND-200 experiment.