SuperCDMS Energy-scale, Resolution, and Sensitivity May 18th 2015 SURF Science Conference @ SDSMT SuperCDMS Energy-scale, Resolution, and Sensitivity A.N. Villano University of Minnesota (for the SuperCDMS collaboration)

CDMS Challenge: low threshold May 18th 2015 SURF Science Conference @ SDSMT CDMS Challenge: low threshold Control our noise: our athermal phonon readout gives world class energy resolution, and it’s going to get better Extend our data reduction: we use algorithms to extract our energy/timing parameters which account for our noise environment, and new algorithms have been developed to optimize further Exploit all calibration handles: toward lower energies it becomes more difficult to find calibration standards, we broadened our low-energy standards for SuperCDMS Soudan and will go further for SuperCDMS SNOLAB

SURF Science Conference @ SDSMT May 18th 2015 SURF Science Conference @ SDSMT SuperCDMS Detectors

SURF Science Conference @ SDSMT May 18th 2015 SURF Science Conference @ SDSMT The iZIP Detector Thickness: 1” / Diameter: 3”

SURF Science Conference @ SDSMT May 18th 2015 SURF Science Conference @ SDSMT Luke Effect & Yield Extra phonons are created in response to the moving charges in the semiconductor detectors, this is called the Luke effect, and needs to be taken into account phonon energy ionization energy true recoil energy yield

SURF Science Conference @ SDSMT May 18th 2015 SURF Science Conference @ SDSMT The iZIP Detector Electrons (e-) Holes (h+) If event near surface, all ionization collected locally Holes (h+) Electrons (e-) If event in bulk, ionization shared equally between sides

Yield & Charge FV Discrimination (iZIP) May 18th 2015 SURF Science Conference @ SDSMT Yield & Charge FV Discrimination (iZIP) Clearly identify bulk ERs & surface NRs (210Pb source) Very few surface events are “charge symmetric” Clearly identify bulk NRs (252Cf calibration)

SURF Science Conference @ SDSMT May 18th 2015 SURF Science Conference @ SDSMT Luke Gain for CDMSlite Forget about quantifying ionization yield, just turn up the voltage to use the high-resolution phonon sensors to get to the lowest threshold! boost voltage to ~100 V or more total phonon energy true recoil energy (unmeasurable) ERs and NRs inseparable and have different energy scales; measure ionization precisely, maybe down to e-/h+ pair events

Threshold Drives Mass Reach May 18th 2015 SURF Science Conference @ SDSMT Threshold Drives Mass Reach

Ge Results with Different Thresholds May 18th 2015 SURF Science Conference @ SDSMT Ge Results with Different Thresholds R. Agnese et. al., Phys. Rev. Lett 112, 241302 (2013) R. Agnese et. al., arXiv: 1504.05871 CDMSlite mode limit (red) and iZIP limit (black) (see Luke Gain for CDMSlite in backup) Get to ~4 GeV/c2 and ~7 GeV/c2 WIMP mass before steep rise Thesholds ~170 eV and ~1 keV CDMS II strongest high-mass limit (black solid), and some low-mass reach (black dashed) Get to ~20 GeV/c2 and ~15 GeV/c2 before steep rise Thresholds 10 keV and 5 keV

Noise Drives Threshold May 18th 2015 SURF Science Conference @ SDSMT Noise Drives Threshold

Phonon Channel (QET) Readout May 18th 2015 SURF Science Conference @ SDSMT Phonon Channel (QET) Readout L/R of SQUID input branch of QET current impacts signal current bandwidth ~ 65 kHz SQUID Input coil L/R bandwidth

Phonon Channel (QET) Readout May 18th 2015 SURF Science Conference @ SDSMT Phonon Channel (QET) Readout Rp (parasitic resistance) SQUID Input coil Readout mechanism: sense current through SQUID input coil which is related to resistance of QET Major sources of Johnson-Nyquist noise indicated at left SQUID input noise at the level of ~ 1 nA/√Hz

Phonon Noise Mitigation May 18th 2015 SURF Science Conference @ SDSMT Phonon Noise Mitigation The Johnson-Nyquist noise depends on resistances and temperature ( ) Some typical values for CDMS II and SuperCDMS Soudan:

Improvements for SNOLAB May 18th 2015 SURF Science Conference @ SDSMT Improvements for SNOLAB What can we tinker with for SNOLAB: Rsh, Tsh: decrease the shunt resistance and move it to base temp Rs, Ts: (harder) decrease resistance and operating temp of sensor Rp: (hardest) decrease parasitic resistance back to ground Tp: (near impossible) resistance spread over many cryostat components at many temperature stages.

SuperCDMS iZIP Data Reduction May 18th 2015 SURF Science Conference @ SDSMT SuperCDMS iZIP Data Reduction

Standard Optimal Filter May 18th 2015 SURF Science Conference @ SDSMT Standard Optimal Filter phonon pulse best-fit template time (0.8 ms/bin) signal template noise fit amplitude Power Spectral Density Used for energy estimators since CDMS-I Great resolution at low energy where noise causes simple integral to fluctuate In phonon signals these quantites have significant position dependence

Non-Stationary Optimal Filter May 18th 2015 SURF Science Conference @ SDSMT Non-Stationary Optimal Filter iZIP lower aluminum coverage, have long phonon tails – good for relative calibration and making analog sum pulse Used on only the summed pulse with iZIPs – where position dependence is small already Creates better resolution energy estimators for events distributed across the crystal Position information mostly at the leading edge of the pulse, so NSOF emphasizes the iZIPs long tail for improved energy resolution freq. correlation matrix Frequency-correlated position-dependent “noise” obtained from OF residuals

Two Low-Threshold Publications using NSOF for Energy Scale May 18th 2015 SURF Science Conference @ SDSMT Two Low-Threshold Publications using NSOF for Energy Scale R. Agnese et. al., Phys. Rev. Lett 112, 041302 (2013) CDMSlite with impressive HV technique for low mass reach SuperCDMS low threshold limit R. Agnese et. al., Phys. Rev. Lett 112, 241302 (2013)

Energy Resolution & Threshold May 18th 2015 SURF Science Conference @ SDSMT Energy Resolution & Threshold For standard iZIP mode have ~200 eVee and for CDMSlite mode have ~42 eVee K.D. Irwin, Appl. Phys. Lett. 66, 1998 (1995) QET heat capacity n and a are QET properties related to heat conduction to the substrate and steepness of the transition in R/T For SNOLAB will get to ~10 eVee resolution for CDMSlite – “fundamental” limit probably ~1 eVee (see Irwin)

Precision Calibration May 18th 2015 SURF Science Conference @ SDSMT Precision Calibration

Low-energy Ge Activation Lines May 18th 2015 SURF Science Conference @ SDSMT Low-energy Ge Activation Lines For CDMSlite running at SNOLAB low-energy calibration lines are key, here we have neutron/cosmogenically activated 68Ge/71Ge EC lines EC is really great because it’s (almost) pure ER and very well-defined energy

SURF Science Conference @ SDSMT May 18th 2015 SURF Science Conference @ SDSMT The Lindhard Curve Charge collection is quenched with respect to the phonon or heat production Measurements done at 77 K and high fields Sparse at E < 1 keV

Examples of Effects on High-Precision Low-Mass Limits May 18th 2015 SURF Science Conference @ SDSMT Examples of Effects on High-Precision Low-Mass Limits CDMSlite limits can change depending on the NR yield model For other analyses the systematics of the signal identification region can be significantly increased with yield model uncertainty

Can use 88Y-Be source potentially May 18th 2015 SURF Science Conference @ SDSMT Can use 88Y-Be source potentially Near-threshold resonance produces essentially isotropic 9Be(g,n) 88Y has two decays that are slightly off-resonance

Neutron Reflector Shielding May 18th 2015 SURF Science Conference @ SDSMT Neutron Reflector Shielding Shielding configurations can bring mono-energetic neutron max scattering edge over background Disclaimer: picture at left taken from a representative setup at test facility, Soudan has better background situation and specialized trigger

SURF Science Conference @ SDSMT May 18th 2015 SURF Science Conference @ SDSMT Projections

SURF Science Conference @ SDSMT May 18th 2015 SURF Science Conference @ SDSMT Summary Control our noise: we’re doing this by lowering Tc and putting resistors that contribute high Johnson noise at lower temperature stages Extend our data reduction: the non-stationary optimal filter provides a position-dependence-mitigated energy estimator, phonon fiducial volumes have produced improvements in analysis Exploit all calibration handles: we are exploiting our internal Ge activation lines at 1 and 10 keV to the fullest extent. The M-shell line at ~160 eV could also prove very useful. We are also exploring lines in Si (difficult) and direct nuclear recoil calibrations

SURF Science Conference @ SDSMT May 18th 2015 SURF Science Conference @ SDSMT Backup Slides

Leverage on Backgrounds May 18th 2015 SURF Science Conference @ SDSMT Leverage on Backgrounds

Surface Events and Neutron Events May 18th 2015 SURF Science Conference @ SDSMT Surface Events and Neutron Events Very few surface events are “charge symmetric” Can clearly identify bulk ERs and bulk NRs

iZIP Surface Event Rejection & Passage Efficiency May 18th 2015 SURF Science Conference @ SDSMT iZIP Surface Event Rejection & Passage Efficiency Neutron passage fraction above ~90% for important low energy region Rejection factor for FV is ~1/33,333 in “beta band” for 10 keV threshold R. Agnese et. al., Appl. Phys.. Lett 103, 164105 (2013)

CDMS-II Detectors (oZIPs) May 18th 2015 SURF Science Conference @ SDSMT CDMS-II Detectors (oZIPs) Biased with an electric field 3 V/cm Dark Matter would appear as “bulk” nuclear recoils (NRs) Need phonon timing to remove surface events Side 1 Side 2 Cryogenic Semiconductor Four athermal phonon TES arrays

Exposures at Soudan run num. towers detector types Ge dets Si dets May 18th 2015 SURF Science Conference @ SDSMT Exposures at Soudan run num. towers detector types Ge dets Si dets Publications (pre-2010) 118 1 oZIP (6) 4 2 PRD 72, 052009 (2005) 119 oZIP (12) 6 PRL 96, 011302 (2006) PRD 73, 011102 (2006) 123 5 oZIP (30) 19 11 PRL 102, 011301 (2009) 124 125 Science 327,1619(2010) 126 127 128 132 3 oZIP (4), mZIP (10), iZIP (3) 17 (engineering) 133 iZIP (15) 15 (3 publications spring ‘13 - fall `14)

SuperCDMS iZIP Detector Tech May 18th 2015 SURF Science Conference @ SDSMT SuperCDMS iZIP Detector Tech

New, Larger (100 mm dia.) iZIPs! May 18th 2015 SURF Science Conference @ SDSMT New, Larger (100 mm dia.) iZIPs! 12 Phonon channels 4 charge channels Interleaved phonon and charge detection Larger size increases science impact for cost More phonon channels give better position information 133Ba peak Noise performance comparable to current iZIP designs Well resolved charge signals achieved at UMN test facility for 356 keV line

New, Larger (100 mm dia.) iZIPs! May 18th 2015 SURF Science Conference @ SDSMT New, Larger (100 mm dia.) iZIPs! 12 Phonon channels 4 charge channels Interleaved phonon and charge detection Larger size increases science impact for cost More phonon channels give better position information Noise performance comparable to current iZIP designs Well resolved charge signals achieved at UMN test facility for 60 keV line 241Am peak

New, Larger (100 mm dia.) iZIPs! May 18th 2015 SURF Science Conference @ SDSMT New, Larger (100 mm dia.) iZIPs! 12 Phonon channels 4 charge channels Interleaved phonon and charge detection Larger size increases science impact for cost More phonon channels give better position information Promises excellent sensitivity for SuperCDMS-SNOLAB!

UMN 100 mm Phonons & Ionization May 18th 2015 SURF Science Conference @ SDSMT UMN 100 mm Phonons & Ionization