Blas Cabrera - Stanford UniversitySuperCDMSPage 1 CDMS-II Completion and SuperCDMS Collaboration Meeting UC Santa Barbara February 12, 2005 Blas Cabrera

Blas Cabrera - Stanford UniversitySuperCDMS Page 1

CDMS-II Completionand SuperCDMS

Collaboration MeetingUC Santa BarbaraFebruary 12, 2005

Blas CabreraStanford University - KIPAC


Path to SuperCDMS• SUF Run 21 - 2002

– Tower 1 (4 Ge and 2 Si detectors) at SUF (neutron limited)• Soudan Run 118 - Oct 2003 to Jan 2004

– Tower 1 at Soudan - PRL 93, 211301 (2004) best by x4– More detailed PRD submission in Feb 2004

• Soudan Run 119 - Mar 2004 to Aug 2004– Towers 1& 2 run has increased Ge data x3 and Si data x8– Analysis well underway plan to announce results at Apr

APS• Soudan Run 120 - 2005

– Towers 1-5 run is expected to increase Ge exposure x6• SuperCDMS Development Project (possible delay in start)

– Towers 1-5 continued running is expected to increase Ge x3

– Development Project - 5 kg Ge new detectors run at Soudan

• AGENCY APPROACHES AND STRATEGIES


133Ba gamma & 252Cf neutron calibrations• Use phonon

risetime and charge to phonon delay for discrimination of surface electrons “betas”

• Cuts and analysis thresholds determined entirely from calibration data with WIMP search data blinded until after the cuts and thresholds were set.

gammas

neutrons

ejectrons


Simulation setting cut with calibration

Calibration - Gaussiandistribution 1000 evts

Data - samedistribution100 evts

Datax10

Calx10

Cut atlast event

Probability0.1 of eventpast cut

On averagearea beyondlast event = 1

On averagearea beyondcut = 0.1


Detector MC progress

• Use detector MC to improve our understanding of the origin of timing and partition response (Matt Pyle)

QuickTime™ and a decompressor

are needed to see this picture.


About to Operate Five Towers in Soudan


Completed fabrication & testing of T3-5

4.5 kgof

Ge !!!(1 kg Si)


CDMS-II Scientific Reach• CDMS-II explores MSSMs

in series of runs

• SUF Tower 1 in 2002

• Soudan Tower 1 in 2003

• Soudan Tower 1-2 in 2004

• Soudan Towers 1-5 2005

• Another factor of 3-5 improvement at Soudan past CDMS-II (neutrons)

• THEN MUST GO DEEPER - Planning SuperCDMS at SNOLab in Canada

EGRET gammas asDM annihilation

astro-ph/0408272

DAMA EDELWEISS


Sensitivity Reach of CDMS-II & SuperCDMS


Summary and bold future vision

Limit at SUF 2002(during CDMS II)

Development Project 5 kg of Ge 2008

SuperCDMS Phase C 1000 kg of Ge

World-best limit today

SuperCDMS Phase A 25 kg of Ge 2011

CDMS II goal 2006

SuperCDMS Phase B 150 kg of Ge 2014


What do we learn if we see a signal?• Our recent 90% C. L.

corresponds to < 1 evt per 8 kg-d for Ge

• Suppose we see 8 events at the rate of 1 evt per 50 kg-d of Ge

• Then mass & cross section determined as shown and SI vs SD determined from different targets

• Suggest properties to look for at LHC and future ILC

If SUSY seen first at LHC would still want to determine if LSP is the dark matter,SO NEED TO PUSH DIRECT DETECTION EITHER WAY

A convincing signal would motivate large TPC such as DRIFT for velocity distribution

actualsignal


Compare with Competition• NaI - annual modulation with no discrimination (<6 pe/keV)

– DAMA signal is suspect because near threshold (systematics)– LIBRA - 250 kg new installation (still no discrimination)

• Cryogenic technologies - lowest intrinsic threshold (106 phon/keV)– (Super)CDMS Ge & Si ionization + phonon + timing (best)– EDELWEISS Ge thermal + ionization (no timing)

– CRESST CaWO3 thermal + scintillation (no light for W)

• Liquid Xenon - intrinsically high threshold (~1 pe/keV)– ZEPLIN I & XMASS scintillation (uncalibrated result)– XENON scintillation + ionization (need demo of threshold &

stability)

• Superheated liquids - no energy resolution (counting)– SIMPLE & PICASO CF3Br & CF3I (need demo of stability)

• Liquid He (HERON) and Ne (NEON) detectors good for SD only • TPC DRIFT - good for future directionality (not enough mass

now)


Propose to operate at SNOLab (6060 mwe)

• At SUF– 17 mwe– 0.5 n/d/kg

• At Soudan– 2090

mwe– 0.5 n/y/kg

• At SNOLab– 6060

mwe– 1 n/y/ton

Log

10(M

uon F

lux)

(m-2s-

1)

Depth (meters water equivalent)


SuperCDMS Roadmap to SNOLAB


Detector development plans


Detector development (Paul)• Existing ZIPs

3” dia x 1 cm thick

• Thicker ZIPs3” dia x 1” thick(base detector)

• Explore larger ZIPs to 4” dia and up to 4 cm thick

CIS - Balzers & Ultratech

Varian - Balzers; CIS - Laurell & EV aligner

Varian - Balzers; CIS - Laurell & EV aligner


0

5

10

15

0

2

4

6

8

10-1

-0.5

0

0.5

1

X Position [mm]Z Position [mm]

Interleaved Ionization electrodes concept• Alternative method to identify near-surface events

– Phonon sensors on both sides are virtual ground reference.– Bias rails at +3 V connected to one Qamp– Bias rails at -3 V connected to other Qamp– Signals coincident in both Qamps correspond to events

drifted out of the bulk. – Events only seen by one Qamp are < 1.0 mm of the surface.


Interleaved Ionization electrode design• Design details

– To maintain ~60 pF of capacitance requires keeping bias and ground rails ~ 1 mm apart.

– Phonon sensors ‘contained’ within the (200 m wide)ground rails.

– First wafer recently completed:

Ground ring around side to define the ‘Qouter’ volume containing all surfaces


Identify and Reduce 210Pb, 14C & 40K

• Use Van de Graaff to attract positive ion radon daughters 222Rn -> 218Po -> 214Pb -> 214Bi -> 214Po -> 210Pb

• Run VdG for 2 hrs• Wipe surface & count

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QuickTime™ and aTIFF (Uncompressed) decompressor


3.8d 3.1m 27m 20m .16ms

250kV

ground


New Read-out schemes

• Two-stage SQUIDs for reading out new phonon sensors– Allows lower Rn, more TESs, better phonon sensor

surface area coverage.• Will improve effectiveness of present phonon risetime

cut even further.– Allows move to Al-Mn TESs to overcome W Tc variability

• Resitivity of Al-Mn < W, hence risk /design constraint of electro-thermal oscillation if change-over to two-stage SQUIDs not implemented.

– Commensurate with NIST-style time-domain multiplexing.

• ZIP detector phonon pulses are probably sufficiently slow to utilize this scheme effectively to reduce the readout wiring to room temperature that would otherwise be required.


• Two-stage SQUID configuration – Ionization detector transformer-coupled to first-stage SQUID

– Eliminate potential microphonic read-out issues associated with FET readout

– Eliminate IR photon leakage

– Eliminate heated FET load on 4 K

– Transformer ~ 12 mm x 6 mmchip, fabricated at NIST.

– Critically damped circuit, ~1 MHz sampling required.

– Simulations give 0.4 keVee FWHM

Ionization read-out using SQUIDs


How to build a 1000 kg experiment in stages


Schematic of new ‘SNObox’

x3

x3

Exploring cryocooler system with little or no cryogen servicing


Conclusion• For CDMS-II important that we

– complete Run 118 PRD– complete Run 119 analysis PRL and futher PRD– start and complete Run 120

• For SuperCDMS we have– submitted base support proposals for NSF groups– submitted Development Project proposal to DOE/NSF– submitted MRI for Cryosystem to NSF– started detector R&D at Stanford– started cryosystem R&D at Fermilab

• And we need to– push on NSF for base support decision and DOE/NSF for

review– Look for new collaborators (Nat Labs, UMN, UCSB, &

Canada)

Documents

Blas Cabrera - Stanford UniversitySuperCDMSPage 1 CDMS-II Completion and SuperCDMS Collaboration Meeting UC Santa Barbara February 12, 2005 Blas Cabrera