CDMS Status Upgrades and Plans Summary of running

CDMS Status, Upgrades and Plans Summary of running at Soudan Cryogenic and Detector Upgrades The Future - Super. CDMS@SNOLAB All experimenters meeting - December 15, 2008 Dan Bauer - CDMS Project Manager

>2 years of stable data taking at Soudan Maximum livetime = 85% (limited by cryo servicing need for calibration data) DAMA MSSM CDMS (2006) Gamma Calibration ~10% of livetime Xenon 10 CDMS (Feb 2008) Current CDMS sensitivity Average livetime ~ 75% All experimenters meeting - December 15, 2008 We now have >1700 kg-days of exposure, sufficient to have world’s best spinindependent WIMP sensitivity for all WIMP masses. Approaching 10 Zeptobarn cross section! Dan Bauer - CDMS Project Manager

Cryogenic Upgrades - UPS • Replaced UPS for cryogenics system – Underground diesel generator backs up entire cryogenics system – Aging UPS was used to ‘bridge’ cryogenics control systems – Installed new 30 k. VA unit to carry whole cryogenics system – Remote control and monitoring of UPS from the surface Underground diesel generator All experimenters meeting - December 15, 2008 UPS remote monitoring Dan Bauer - CDMS Project Manager

Cryogenic Upgrades - Replaced Ebox • Have lived for 2 years with small leaks in vacuum bulkhead (Ebox) – Air freezes out on cold surfaces, can cause vacuum bursts – If Helium gets in, it can reach detectors and affect signals – Occasional ~1 week warming to 4 -77 K has been necessary • Problem was due to custom-design of Ebox – Warping of rectangular box made large o-ring seals difficult • Solution was to buy large commercial vacuum cross – Had vendor weld high-vacuum detector electrical connections into commercial vacuum plates • Decided to warm to room temperature in October to install – Takes about 2 weeks to warm, another 2 weeks to cool down – Actual work at room temperature about 2 weeks All experimenters meeting - December 15, 2008 Dan Bauer - CDMS Project Manager

Cryogenics Upgrades - Ebox Old ebox (note the black sealant) All New Eboxmeeting - installed 2008 experimenters being December 15, Stripline detector connections extracted Reinstalling the- stripline connections Dan Bauer CDMS Project Manager

Cryogenic Upgrades - Serviced Cryocooler • Cryocooler removes excess heat at 4 K and 77 K – We cannot run 30 detectors without this • Servicing involves replacing cold head at room temperature • Why did we want to do this now? – Had 150% of recommended hours on the cold head – Valves or piston could begin sticking at some point – No evidence of performance problems but want to run another 23 years at Soudan, so this was a good time to do this – Fortunately, the vendor (Sumitomo) can replace the cryocooler head without disturbing the delicate connections to e-stem – Challenge was supporting these connections during the operation • New head should last for length of CDMS operation at Soudan All experimenters meeting - December 15, 2008 Dan Bauer - CDMS Project Manager

Cryogenic Upgrades - Cryocooler Supporting the cryocooler and estem during the cold head replacement All experimenters meeting - December 15, 2008 The cryocooler cold head Dan Bauer - CDMS Project Manager

An interesting incident during cooldown • Dilution refrigerator uses 1 K pot to condense 3 He – 1 K pot is filled from He bath via needle valves – Pumping on 4 He in pot lowers temperature to 1. 4 K • At this temperature, liquid Helium is a superfluid – Superfluid Helium tends to creep – Distance it can travel depends on surface roughness • Small amount of air was accidentally introduced in bath – Plated out in needle valves, allowing superfluid Helium connection between 1 K pot and 4 K bath • Result was a 1 K pot temperature >1. 9 K and very poor condensation of 3 He • Had to warm again above 77 K and pump away air – Now understand earlier instability with pot temperatures All experimenters meeting - December 15, 2008 Dan Bauer - CDMS Project Manager

Additional work planned in 2009 • Soudan underground power feed – Near maximum capacity and getting old – Study underway to determine whether upgrades needed – May be possible to run separate feed for water pumps • CDMS would like to install He liquefiers at Soudan – He costs are skyrocketing and availability is an issue • 36% increase in costs this summer • Several recent instances where supply was very tight • CDMS uses about 70 l/day – Purchased 3 cryocooler-based liquefiers in FY 2008 • Plan phased installation during 2009 -2010 • Sufficient capacity to reduce He consumption by x 10 – Requires additional power (8 kw/liquefier) All experimenters meeting - December 15, 2008 Dan Bauer - CDMS Project Manager

Detector Issues • Many detectors have failed in the oldest two towers – These towers are now 6 years old and have seen many thermal cycles – Will do postmortem on failures when towers replaced; most suspected to be cold electronics and wire bonds – Net loss of about 1 kg Ge for the next three months • New issues with Si detectors in this run – Many of our Si detectors show signs of charge leakage through the crystal – Run at reduced charge bias to avoid heating of phonon sensors – Si detectors are no longer crucial for WIMP search All experimenters meeting - December 15, 2008 Dan Bauer - CDMS Project Manager

Larger detectors to be deployed in 2009 Remove two oldest towers lose 1. 5 kg Ge, 0. 6 kg Si (mostly not working anyway) New Super. CDMS detectors each 3” dia x 1” => 0. 64 kg of Ge with new phonon sensor design to improve fiducial volume All experimenters meeting - December 15, 2008 Dan Bauer - CDMS Project Manager

Super. CDMS@Soudan • Replace CDMS II detectors with Super. CDMS detectors – 0. 25 kg Ge/0. 1 kg Si --> 0. 64 kg Ge – Each new tower has 5 Ge detectors => ~3 kg mass – Each also has two Ge endcap veto detectors • Improves ability to reject backgrounds from nearby materials • First ‘Supertower’ due in March 2009 – Will bring Ge mass to 6 kg • Remaining 4 supertowers in early 2010 – Total deployed Ge mass will be 15 kg • Two year run will yield x 3 sensitivity improvement over the best that CDMS II will produce (x 10 better than currently published). All experimenters meeting - December 15, 2008 Dan Bauer - CDMS Project Manager

The Future: Super. CDMS@SNOLAB • Science goals – Increase sensitivity by x 50 (compared with current published) – Reach WIMP-nucleon cross section of 10 -46 cm 2 – Find WIMP signal and compare with LHC • Technical goals – Increase detector mass in stages up to 100 kg by 2012 – Stay background free – Challenge to deal with existing backgrounds at Soudan – New setup needed at SNOLAB to reduce neutron background • Current status – First Soudan stage funded by DOE/NSF; full 15 kg funding requested – SNOLAB experiment has CD-0 and Stage 1 approval from FNAL Director – DMSAG 2 review of the field in 2009 will likely determine funding prospects All experimenters meeting - December 15, 2008 Dan Bauer - CDMS Project Manager

CDMS is the only DM experiment with demonstrated control of backgrounds Make sure any events here are WIMPS, not background! All experimenters meeting - December 15, 2008 Dan Bauer - CDMS Project Manager Expected Background: 0. 6 ± 0. 5 surface events and < 0. 2 neutrons