skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Sub-Kelvin High-Mass CCD Detectors for Dark Matter & Neutrino Searches

Abstract

Observations of galaxies, superclusters, distant supernovae, and the cosmic microwave background radiation indicate that 85% of the matter in the universe is nonbaryionic. Understanding the nature of this so-called dark matter is of fundamental importance to cosmology, astrophysics, and high energy particle physics and is specifically highlighted in the SNOWMASS 2013 High Energy Physics community report. Although Weakly Interacting Massive Particles (WIMPs) of mass 10-100 GeV/c2 have been the main interest of the majority of direct dark matter detection experiments, recent signal claims, together with compelling new theoretical models, are shifting the old paradigm towards broader regions in the dark matter parameter space well below 10 Gev. The SuperCDMS SNOLAB experiment is seeking to directly detect dark matter using very sensitive, low threshold germanium or silicon semiconductor detectors operating at millikelvin temperatures. An improved version of this detector technology makes an entirely new frontier accessible that hitherto has only been in the planning stages at various facilities. Nearly thirty years ago, Freedman determined that the neutrino-nucleon neutral current interaction leads to a coherence effect, whereby the elastic scattering cross section is enhanced and scales approximately as the square of the number of neutrons in the nucleus. Hence, for typical nuclearmore » radii, coherent scattering leads to nuclear recoils in the range of a few keV for incoming neutrinos with energies in the range ~ 1-100 MeV. Although CEνNS is a fundamental prediction of the Standard Model, it has not been measured until recently and may open a window to new physics. The expected CEνNS cross-section is many orders of magnitude higher than the coherent WIMP nucleon scattering cross-section excluded by current generation experiments for standard heavy WIMPs. However, this process has a low recoil energy endpoint ( We expect interactions from both light mass WIMPs and CEνNS to produce nuclear recoils of a few tens of eV, as measured by the nuclear recoil channel. Thus, both experiments strive to develop very low threshold detectors, preferably with single electron-hole pair resolution. Due to the Ge/Si crystallographic orientation dependence of e-h excitations at such extremely low thresholds, these data can help steer the design of future (G2+ and G3) detectors wherein the solar neutrino scattering becomes a major background for DM experiments. Since September 2016, Mirabolfathi has initiated a collaborative effort with the K. Nordlund computational physics and matter-radiation interaction group at the University of Helsinki to study energy threshold for e-h excitations from nuclear recoils in Ge or Si crystals. Our computational results show that those thresholds are well below the Lindhard estimate and exhibit strong crystallographic orientation dependence. This could pave the way for directional sensitivity to the WIMP-detector interaction and ultimately provide a gateway for a directional DM search with condensed matter detectors, i.e. the holy grail in the DM direct search community. On the other hand, observational astronomy has long implemented Charge Coupled Devices (CCD), and recently dark matter searches have started to do the same. The excellent ionization resolution offered by CCDs makes them one of the most suitable technologies for very low mass dark matter searches. However, they are difficult to scale up in mass because the detectors need to be depleted to suppress thermally generated carriers in semiconductors. Even made from the purest Si substrates available, detectors thicker than 1 mm are difficult to deplete. Recently, single electron detection has been demonstrated with skipper CCD’s with unprecedented < 1 electron resolution. DAMIC (Dark Matter) and CONNIE (CEνNS) are experiments that use CCD technology for event searches but, because of depletion limitations, suffer from a small payload mass. The only way for these experiments to increase mass is by making more modules, which increases the readout electronics necessary and hence the cost. We propose a method to increase CCD mass per module by freezing the minority carriers rather than depleting them. Among the most suitable devices to search for low-mass WIMPs are the SuperCDMS experiment phonon-mediated detectors. They offer very low threshold to detect low mass WIMPs as well as high resolution due to phonon mediated sub-kelvin detector technology. SuperCDMS uses two detector types specifically designed for different WIMP mass ranges: 1) The iZIP technology, which uses simultaneous measurement of ionization and phonons to discriminate Nuclear Recoil (NR) expected WIMP interaction events from Electron Recoil (ER) radioactive background events, and 2) SuperCDMS HV technology, which is based on indirect, but very sensitive, measurement of ionization via Neganov-Luke (NL) phonon amplification. In the absence of leakage current, the detector sensitivity improves proportionally to the applied bias across the detector and can in principle reach the ultimate quantum limit of single electron hole pair threshold of ~eV. Our current SuperCDMS HV detector technology is underperforming at large voltages due to an early onset of leakage current that deteriorates our signal-to-noise gain. We are proposing a method to solve both the scalability of CCD technology and HV leakage in NL amplification assisted CDMS detectors. The idea combines both technologies to make sub- kelvin phonon-assisted CCD readout. CDMS already proved that at sub-kelvin temperatures, carriers drift over large distances for fields as low as ~V/cm without significant ionization loss. This matches our expectation from semiconductor physics since all carriers and impurities are frozen at these low temperatures, making depletion superfluous. CCD electrode architecture also alleviates the ionization leakage drawback in CDMS HV technology since, assuming a long enough carrier lifetime and a low amplitude alternating bias, one can achieve similar phonon gain compared to HV DC bias.« less

Authors:
Publication Date:
Research Org.:
Texas A & M Univ., College Station, TX (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1595467
Report Number(s):
SC0018975
DOE Contract Number:  
SC0018975
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; CCD, Dark Matter, Neutrino, phonon sensors

Citation Formats

Mirabolfathi, Nader. Sub-Kelvin High-Mass CCD Detectors for Dark Matter & Neutrino Searches. United States: N. p., 2020. Web. doi:10.2172/1595467.
Mirabolfathi, Nader. Sub-Kelvin High-Mass CCD Detectors for Dark Matter & Neutrino Searches. United States. doi:10.2172/1595467.
Mirabolfathi, Nader. Wed . "Sub-Kelvin High-Mass CCD Detectors for Dark Matter & Neutrino Searches". United States. doi:10.2172/1595467. https://www.osti.gov/servlets/purl/1595467.
@article{osti_1595467,
title = {Sub-Kelvin High-Mass CCD Detectors for Dark Matter & Neutrino Searches},
author = {Mirabolfathi, Nader},
abstractNote = {Observations of galaxies, superclusters, distant supernovae, and the cosmic microwave background radiation indicate that 85% of the matter in the universe is nonbaryionic. Understanding the nature of this so-called dark matter is of fundamental importance to cosmology, astrophysics, and high energy particle physics and is specifically highlighted in the SNOWMASS 2013 High Energy Physics community report. Although Weakly Interacting Massive Particles (WIMPs) of mass 10-100 GeV/c2 have been the main interest of the majority of direct dark matter detection experiments, recent signal claims, together with compelling new theoretical models, are shifting the old paradigm towards broader regions in the dark matter parameter space well below 10 Gev. The SuperCDMS SNOLAB experiment is seeking to directly detect dark matter using very sensitive, low threshold germanium or silicon semiconductor detectors operating at millikelvin temperatures. An improved version of this detector technology makes an entirely new frontier accessible that hitherto has only been in the planning stages at various facilities. Nearly thirty years ago, Freedman determined that the neutrino-nucleon neutral current interaction leads to a coherence effect, whereby the elastic scattering cross section is enhanced and scales approximately as the square of the number of neutrons in the nucleus. Hence, for typical nuclear radii, coherent scattering leads to nuclear recoils in the range of a few keV for incoming neutrinos with energies in the range ~ 1-100 MeV. Although CEνNS is a fundamental prediction of the Standard Model, it has not been measured until recently and may open a window to new physics. The expected CEνNS cross-section is many orders of magnitude higher than the coherent WIMP nucleon scattering cross-section excluded by current generation experiments for standard heavy WIMPs. However, this process has a low recoil energy endpoint ( We expect interactions from both light mass WIMPs and CEνNS to produce nuclear recoils of a few tens of eV, as measured by the nuclear recoil channel. Thus, both experiments strive to develop very low threshold detectors, preferably with single electron-hole pair resolution. Due to the Ge/Si crystallographic orientation dependence of e-h excitations at such extremely low thresholds, these data can help steer the design of future (G2+ and G3) detectors wherein the solar neutrino scattering becomes a major background for DM experiments. Since September 2016, Mirabolfathi has initiated a collaborative effort with the K. Nordlund computational physics and matter-radiation interaction group at the University of Helsinki to study energy threshold for e-h excitations from nuclear recoils in Ge or Si crystals. Our computational results show that those thresholds are well below the Lindhard estimate and exhibit strong crystallographic orientation dependence. This could pave the way for directional sensitivity to the WIMP-detector interaction and ultimately provide a gateway for a directional DM search with condensed matter detectors, i.e. the holy grail in the DM direct search community. On the other hand, observational astronomy has long implemented Charge Coupled Devices (CCD), and recently dark matter searches have started to do the same. The excellent ionization resolution offered by CCDs makes them one of the most suitable technologies for very low mass dark matter searches. However, they are difficult to scale up in mass because the detectors need to be depleted to suppress thermally generated carriers in semiconductors. Even made from the purest Si substrates available, detectors thicker than 1 mm are difficult to deplete. Recently, single electron detection has been demonstrated with skipper CCD’s with unprecedented < 1 electron resolution. DAMIC (Dark Matter) and CONNIE (CEνNS) are experiments that use CCD technology for event searches but, because of depletion limitations, suffer from a small payload mass. The only way for these experiments to increase mass is by making more modules, which increases the readout electronics necessary and hence the cost. We propose a method to increase CCD mass per module by freezing the minority carriers rather than depleting them. Among the most suitable devices to search for low-mass WIMPs are the SuperCDMS experiment phonon-mediated detectors. They offer very low threshold to detect low mass WIMPs as well as high resolution due to phonon mediated sub-kelvin detector technology. SuperCDMS uses two detector types specifically designed for different WIMP mass ranges: 1) The iZIP technology, which uses simultaneous measurement of ionization and phonons to discriminate Nuclear Recoil (NR) expected WIMP interaction events from Electron Recoil (ER) radioactive background events, and 2) SuperCDMS HV technology, which is based on indirect, but very sensitive, measurement of ionization via Neganov-Luke (NL) phonon amplification. In the absence of leakage current, the detector sensitivity improves proportionally to the applied bias across the detector and can in principle reach the ultimate quantum limit of single electron hole pair threshold of ~eV. Our current SuperCDMS HV detector technology is underperforming at large voltages due to an early onset of leakage current that deteriorates our signal-to-noise gain. We are proposing a method to solve both the scalability of CCD technology and HV leakage in NL amplification assisted CDMS detectors. The idea combines both technologies to make sub- kelvin phonon-assisted CCD readout. CDMS already proved that at sub-kelvin temperatures, carriers drift over large distances for fields as low as ~V/cm without significant ionization loss. This matches our expectation from semiconductor physics since all carriers and impurities are frozen at these low temperatures, making depletion superfluous. CCD electrode architecture also alleviates the ionization leakage drawback in CDMS HV technology since, assuming a long enough carrier lifetime and a low amplitude alternating bias, one can achieve similar phonon gain compared to HV DC bias.},
doi = {10.2172/1595467},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2020},
month = {1}
}