1. Direct Detection of Dark Matter: CDMS and COUPP
Test
Direct Detection
of Dark Matter:
CDMS and COUPP
Andrew Sonnenschein

2. CDMS Collaboration at Soudan
Test
CDMS Collaboration at Soudan
DOE Laboratory
Fermilab
LBNL
DOE University
Brown
CalTech
Florida
Minnesota
MIT
Stanford
UC Santa Barbara
NSF
Case Western Reserve
Colorado (Denver)
Santa Clara
UC Berkeley
Canada
Queens
September 26, 2007
CDMS and COUPP

3. CDMS-II Detectors Direct detection of WIMP signal
Test
CDMS-II Detectors
Phonon signal
From a quadrant
Phonon signal from
one quadrant D C A B
Charge signal
From inner electrode
Direct detection of WIMP signal
Nuclei recoil by elastic scattering
Read both phonon signal (4 channels) and ionization signal (inner and outer electrode)
1cm thick, 7.8 cm diameter
250g Germanium, 100g Silicon
September 26, 2007
CDMS and COUPP

4. CDMS Subsystems Detectors Ge and Si crystals, 6/tower
Test
CDMS Subsystems
Detectors
Ge and Si crystals, 6/tower
Measure ionization and phonons
Electronics/DAQ
Record signals from detectors and veto; form trigger x5
Cryogenics Maintain detectors at 50 mK
Shielding
Layered shielding (Cu, Pb, polyethylene) reduces radioactive backgrounds and active scintillator veto is >99.9% efficient against cosmic rays.
September 26, 2007
CDMS and COUPP

5. CDMS II Ongoing Run 814 kg-day exposure September 26, 2007
Test
CDMS II Ongoing Run
Expected sensitivity
Xenon10 limit
Published CDMS limit
DAMA
MSSM
814 kg-day exposure
Large calibration data sets
High efficiency for collecting data
September 26, 2007
CDMS and COUPP

6. Test
SuperCDMS 25 kg
Proposed 25-kg experiment based on updated 42 x 600-g Ge ZIPs
120x beyond current limits
15x beyond CDMS-II goal
Approved for space at SNOLAB
Next step towards ton-scale goal
Detector fabrication and characterization underway
Detectors have 3x fiducial volume of CDMS-II design.
Cost per kg reduced to ~1/3.
4x - rejection (H-si; phonon converage)
2x - analysis
5x - bkg reduction (thickness; as clean as cleanest)
->40x, but need only 20x
September 26, 2007
CDMS and COUPP

7. Fermilab responsibilities
Test
Fermilab responsibilities
Established roles in CDMS
Project Management
Operations
Lead the Soudan operations
Cryogenics
Design, construction of the cryogenics systems
Electronics, DAQ, Computing
Warm electronics, event builder software, online and offline processing
Infrastructure
Clean rooms, control rooms, computing rooms
Analysis
Independent analysis chain
New roles for SuperCDMS
Backgrounds
Collaborating with COUPP on understanding Radon, alpha screening
Shield/Veto
Do mechanical design and construction together with cryogenics
Detectors
Exploring possibilities for automated inspection and repair at SiDet
May also get involved in bonding our sensors to larger crystals
Systems Test
Put everything together at Fermilab and test before taking to SNOLAB
Need more scientist and engineering help to push forward these new areas
September 26, 2007
CDMS and COUPP

8. SuperCDMS Cryogenics Design
Test
SuperCDMS Cryogenics Design
Cryogen-free dilution refrigerator
Much lower operations and maintenance cost
Larger volume to accommodate more detectors
More robust thermal connections than in CDMS II
September 26, 2007
CDMS and COUPP

9. Test
Progress on SuperCDMS
New warm electronics prototype for SuperCDMS
Replaces a chain of four 9U-sized boards used for CDMS II
Fewer connections, lower power draw => more robust
Pulse tube cryocooler under test in clean room in Lab 3 at Fermilab
September 26, 2007
CDMS and COUPP

10. SuperCDMS Sensitivity
Test
SuperCDMS Sensitivity
1 ev/kg/month
1 ev/kg/year
1 ev/ton/year
DAMA
KIMS
CRESST
EDELWEISS
ZEPLIN II
WARP
CDMS Soudan
XENON10 APS2007
CDMS Soudan Proj
SuperCDMS SNOLab Proj
LUX 300kg Proj
1 ev/10 kg/year
September 26, 2007
CDMS and COUPP

11. Dark Matter in Bubble Chambers
Test
Dark Matter in Bubble Chambers
Nuclear recoil
E ~ keV 
heavy
target
nucleus
e.g. 127I
WIMP
Recoil range < 1 micron
in a liquid, so the signal is a single bubble rather than a track.
Measure the rate at which single bubbles appear

12. COUPP: Dark Matter Detection with Bubble Chambers
Test
COUPP: Dark Matter Detection with Bubble Chambers
Muon
WIMP?

13. The COUPP Team Wilson Fellows: Andrew Sonnenschein Staff Scientists:
Test
The COUPP Team
Principal Investigator:
Juan Collar
(spokesperson)
Graduate Students:
Nathan Riley
Matthew Szydagis
Undergraduates:
Luke Goetzke
Hannes
Schimmelpfennig
KICP Fellows:
Brian Odom
Wilson Fellows:
Andrew Sonnenschein
Staff Scientists:
Peter Cooper
Mike Crisler
Martin Hu
Erik Ramberg
Bob Tschirhart
Principal Investigator:
Ilan Levine
Undergraduates:
Earl Neeley
Tina Marie Shepherd
Engineers:
Ed Behnke
Fermi National Accelerator
Laboratory
Indiana University
South Bend
Funding
University of Chicago
National Science Foundation
Kavli Institute for Cosmological Physics
Department of Energy
September 26, 2007
CDMS and COUPP

14. 1-Liter Chamber in NuMi Tunnel
Test
1-Liter Chamber in NuMi Tunnel
Design concept:

15. Test
A Typical COUPP Event
Appearance of a bubble causes the chamber to be triggered.
Bubble positions are measured in three dimensions from stereo camera views

16. Spatial Distribution of Bubbles
Test
Spatial Distribution of Bubbles
Two populations:
Walls: apparently from radium contamination of quartz.
Bulk: radon dissolved in chamber liquid

17. Data from 2006 Run SD(p)=3 pb
Test
Data from 2006 Run
First physics results were shown at Fermilab last week.
Data from pressure scan at two temperatures:
Energy Threshold
In KeV
Radon
background
Solid lines:
Expected WIMP response for 
SD(p)=3 pb
September 26, 2007
CDMS and COUPP

18. Test
Results from 2006 Run
We have competitive sensitivity for spin-dependent scattering, despite high radon background
Spin-dependent
Spin-independent
September 26, 2007
CDMS and COUPP

19. New Low-Background Vessel
Test
New Low-Background Vessel
Water
CF3I
Teflon-coated inconel seals replace Viton.
Radon emanation <1% of previous design
Quartz etched with HF acid by vendor to remove implanted radon daughters.
All parts cleaned and assembled in Accelerator Division RF cavity cleaning facility.
Very high purity, well-studied water from Sudbury Neutrino Observatory.
Bellows made using non-thoriated welding electrodes.

20. New Run of 1-liter Chamber
Test
New Run of 1-liter Chamber
Inner vessel has been entirely rebuilt with materials believed to have lower radioactivity.
New run started July 30, 2007.
Some radon introduced during filling, now decaying to equilibrium.

21. Test
COUPP 60 Kg Chamber
Construction of 60 kg chamber approved by the PAC and director in Fall, Now being built.