SuperCDMS at SNOLAB. What is CDMS? Technical Progress. Collaboration. Funding. Schedule and Needs. Why is SuperCDMS 25 kg timely?

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1 What is CDMS? SuperCDMS at SNOLAB Why is SuperCDMS 25 kg timely? Technical Progress CDMS II running at Soudan (4.5 kg Ge) Detectors Cryogenics Backgrounds Electronics Infrastructure Collaboration Addition of new groups Funding Process in the US and prospects Schedule and Needs

2 CDMS- Direct Detection of WIMP Dark Matter Cryogenics Maintain detectors at 50 mk Detectors Ge and Si crystals, 6/tower Measure ionization and phonons Nuclear recoils from WIMP interactions give distinctive signal from most backgrounds Electronics /DAQ Record signals from detectors and veto; form trigger Shielding Layered shielding (Cu, Pb, polyethylene) reduces radioactive backgrounds and active scintillator veto is >99.9% efficient against cosmic rays.

3 Key to our success- Active Background Rejection Detectors with excellent event-byevent background rejection Use charge/phonon AND phonon timing Measured background rejection: % for γ s, 99.79% for β s Clean nuclear recoil selection with ~ 50% efficiency Tower of 6 ZIPs Tower 1 4 Ge 2 Si Tower 2 neutrons betas gammas gammas betas 2 Ge 4 Si neutrons

4 Larger target mass What is SuperCDMS 25 kg? CDMS II at Soudan is running with 4.5 kg Ge => SuperCDMS 25 kg Ge Thicker detectors, improved phonon sensor design (validate at Soudan) Reduced backgrounds Better control of radioactivity in and around experiment Better rejection of electromagnetic backgrounds Deeper site (Soudan=2000 mwe => SNOLAB=6000 mwe) No cosmic-induced neutrons at SNOLAB New cryogenic system Larger (to accommodate more detectors) and better thermal performance More robust and less expensive to operate Improved electronics, DAQ, controls Reduce mechanical connections and heat load; improve reliability Better remote monitoring and control

5 Why are we doing this deep underground? Neutrons from cosmic rays are irreducible background At SUF CDMS 1 17 mwe 0.5 n/kg-d At Soudan 2090 mwe 0.05 n/kg-y At SNOLab Log 10 (Muon Flux) (m -2 s -1 ) SuperCDMS CDMS mwe 0.2 n/ton-y Depth (meters water equivalent)

6 Five Towers now operating in Soudan Shows that we can scale up target mass in cryogenic experiments Text 4.5 kg Ge 1.1 kg Si Significant improvements in cryogenics Thermal modeling Use of cryocooler

7 The Reach of CDMS at Soudan Five tower run through 2007 => x8 better sensitivity ZEPLIN-1 Edelweiss CDMS II - Current CDMS II -projected Will reach minimum cross section of 2 x cm 2 for 60 GeV WIMP Natural MSSM models indicate signal may appear For example, Baltz et. al. (hep-ph/ ) predict ~7 events in CDMS II at Soudan for their LCC2 msugra model

8 Scientific Reach of SuperCDMS Direct Detection complementary to collider searches for SUSY neutralinos Projected upper limits on WIMP cross section and mass for SuperCDMS experiments Soudan 20kg Gray background shape shows allowed regions of msugra parameter space for spinindependent WIMP-nucleon cross sections. Colored regions show representative models in several specific models considered by collider studies. Colored circles indicate the Linear Collider Cosmology benchmark points. Region A is the overlap region between LHC & SuperCDMS 25kg. Region B is accessible only to SuperCDMS 25 kg and Region C only to LHC.

9 CDMS-II ZIPs: 3 dia x 1 cm => 0.25 kg of Ge Detectors for SuperCDMS Existing ZIPs (19 Ge, 11 Si) SuperCDMS ZIPs: 3 dia x 1 => 0.64 kg of Ge 4 prototype ZIPs for SuperCDMS already made

10 Data from UCB/Case TFs for Si 1 ZIP First data from 1 Si ZIP showing reconstructed location of 109 Cd events and spectrum Y Delay [μs] X Delay [μs] Qin [kevee] Yield Risetime [μs] Number Recoil [kev] neutron s Yield

11 Present Cryogenics System at Soudan Dilution Refrigerator (< 50 mk) Cryocooler (77K and 4K) Icebox (Detector Cold Volume)

12 Exploring cryocooler system with little or no cryogen servicing Cryogenic design for SuperCDMS underway Electronics box Outer polyethylene

13 inner poly Shielding and Veto Design Inner shielding with vacuum to maintain cleanliness outer vacuum " inner Pb outer Pb " outer poly Veto mainly to identify neutrons from radioactivity 1 meter thick polyethylene shield to moderate neutrons

14 Fermilab thermal model

15 Gammas SuperCDMS Backgrounds Mainly from radioactivity inside of Pb shielding, predominantly Radon Demonstrated detector rejection is good enough Betas Mainly from radioactivity on detector surfaces or nearby Additional factor of x20 needed from rejection and reduction We can demonstrate these factors within the next year Neutrons 6000 mwe depth of SNOLAB => no cosmic-induced neutrons! Progress on understanding shielding necessary to reduce low energy neutrons from fission decays and (alpha, n) reactions Combination of additional polyethylene shielding and cleanliness Our goal is to remain background-free Systematics of background subtraction limit sensitivity improvements Crucial for convincing interpretation of the first few signal events!

16 Improved background rejection and reduction Background rejection 4 Analysis discrimination 2 Background reduction 5 Total Improvement = 40 Production rate per kg 5 Table 2: Targeted improvement factors over CDMS II advanced analysis levels (see Section 3.2) to achieve SuperCDMS 25 kg sensitivities with zero background from internal sources. The cosmogenic fast-neutron background is eliminated by the SNO- LAB overburden of 6000 mwe. only need x20 of x40 Increase phonon collection area x2 and new H-a-Si electrodes suppress charge backdiffusion x2 Expect at least an additional x2 from advanced timing analyses (see next slide) Expect x2.5 from additional thickness and x2 from better control of Rn Need x20 of this x40 total for the SuperCDMS 25 kg target background Expect x2.5 from additional thickness and x2 from improved fabrication efficiency

17 SuperCDMS Backgrounds Before Veto After Veto Rejection Inefficiency Not Rejected Background Events Rate # Evts Rate # Evts (singles) Rate # Evts CDMS II T 1-5 at Soudan 4.0 kg 485 d (raw 1,300 kg-d) gammas n/a n/a , E-6 4.2E betas n/a n/a E-3 1.2E neutrons (radio-nuclides) n/a n/a 2.0E E neutrons (muon-induced) 1.1E E E SuperCDMS ST6 1-2 at Soudan 7.5 kg 550 d (raw 2,800 kg-d) gammas n/a n/a , E-7 2.1E betas n/a n/a E-4 5.8E neutrons (radio-nuclides) n/a n/a 2.0E E neutrons (muon-induced) 1.1E E E SuperCDMS ST6 1-5 at Soudan 19 kg 1200 d (raw kg-d) gammas n/a n/a 147 1,550, E-7 2.1E betas n/a n/a , E-4 5.8E neutrons (radio-nuclides) n/a n/a 2.0E E neutrons (muon-induced) 1.1E E E SuperCDMS ST6 1-7 at SNOLAB 27 kg 1000 d (raw kg-d) gammas n/a n/a , E-7 1.0E betas n/a n/a , E-4 5.8E neutrons (radio-nuclides) n/a n/a 1.5E E neutrons (muon-induced) 6.8E E E

18 Why is it important to stay background-free? &'()*CC 7"*E>2*%: &,//.23*45653*7"8$*9,1*%: &'()*$%%+ ),-./&'()*$#01*$%"$ 888 B **2;*<,=3/>?35;2 **=>?01/;,2@*<,=3/>?35;2 **A./;*=>?01/;,2@* ),-./&'()*$%*01 );,@>2**$%"$!"#!"$% The 5-SuperTower option at Soudan, with higher risk and reduced sensitivity, is the cyan curve labeled SuperCDMS Soudan 2012, which is an extension of the original cyan curve showing the sensitivity based on Soudan background estimates. The two indicated boxes are the 2- and 5-ST runs in this scenario. In this scenario, the 2-ST run ends earlier than in the SNOLAB scenario, to make way for the earlier arrival of 5 SuperTowers. The original sensitivity from running the first two SuperTowers through the end of 2009 in the SNOLAB scenario is indicated by SuperCDMS Soudan ),-./&'()*"#%01 Systematics of background subtraction limit sensitivity prematurely!

19 New Warm Electronics One new card replaces functions for old front end card, trigger & filter card and the digitizer Units - powered, controlled and read out over ethernet Prototype being tested now at Fermilab Validate against present electronics at test facilities and Soudan USB RJ-11 LEMO Ethernet SysClk I/O Sync I/O Sdat I/O GP I GP O ExtClk EthWr WizNet W3150B EthRd Text EthAd ARM7 uc SD RAM 16Mx16 D A A D Warm Electronics Digital Section Block Diagram Rd Wrt Altera EP1C6 FPGA Ø Det Ref FB SIO SIO SIO SIO SIO SIO LP 16 Bit A/D 16 Bit A/D 16 Bit A/D 16 Bit A/D 16 Bit A/D VXO Phonon A Phonon B Phonon C Phonon D 16 Bit A/D Charge I SClk SDat Charge O To Control CPLD in Analog Section

20 SuperCDMS in Expanded Ladder Lab SuperCDMS 25 kg Experiment

21 Infrastructure at SNOLAB Tailored to layout of tallest Ladder Lab (C2) Need 25 head height for dilution refrigerator, shield lid removal Crane coverage needed for entire length of ladder lab Assembly of heavy shield lids may require 20 ton crane Class-100 clean room (or benches) for detector assembly Cryogenics! and! Mechanical! Area! 25' H! 25' W! 15' L 10' Main Experimental Clean Room 25' H x 25' W x 50' L 14' Mezzanine! 10' H x 23' W x 20' L Electronics! and DAQ! 8' H! 12' W! 10' L Detecctor! Prep Room! 8' H! 12' W! 10' L

22 SuperCDMS Collaboration Collaboration is growing; 3 new groups added! CDMS Institutions DOE Laboratory Fermilab NIST DOE University CalTech Florida Minnesota MIT Stanford UC Santa Barbara NSF Case Western Reserve Colorado (Denver) Santa Clara UC Berkeley Canada Queens (Wolfgang Rau)

23 Cost and Funding Profile for SuperCDMS Experiment costs Operation NSF yr 5-6 $2M $5M Base NSF 6 yrs Personel: 10 Faculty 5 Senior Physicists 14 Techn Staff (project) 14 Postdocs 18 Graduate students! CDMS II! 50% of total cost $16M Project 4 yrs $12M Base Fermilab $9M Base DOE Univ 6yrs

24 Funding Prospects Meetings with DOE and NSF in December 2005 Developed project funding profile which appeared to meet all funding agency constraints R&D funding begins FY2007, construction in FY2008 Discussions since then suggest possible delays in construction funding Presentation to P5 in June 2006 (Particle Physics Project Prioritization Panel) Led to preliminary report which recommends construction start in FY2008 Report approved by HEPAP Review by DMSAG in July 2006 (Dark Matter Scientific Assessment Group) Charged to provide review of SuperCDMS 25 kg in time for final P5 report (end of August) Proposal for SuperCDMS 25 kg submitted to DOE and NSF at end of September, 2006 Anticipate start of funding in early 2007 Need early funding for purchase of big-ticket cryogenics and detector items

25 SuperCDMS Project Schedule CDMS II: T1-T5 Soudan Base grant and Fermilab operating funds Build and test ST1, ST2 SuperCDMS experiment design Deploy, operate T3-5 and ST1-2 at Soudan SuperCDMS R&D DOE $2M NSF $4M Build and test ST3-ST7 SuperCDMS Construction System Test SuperCDMS Construction DOE $5M NSF $5M Move to SNOLAB Deploy and operate ST1-ST7 at SNOLAB

26 Experiment Staging Important lesson learned from CDMS II at Soudan Don t try ANYTHING for the first time in a remote underground laboratory! Crucial to put whole system together at Fermilab and test before installing at SNOLAB Cryogenics system must be battle-tested with at least one detector installed Electronics noise baseline established Readout hardware and software verified Supports tested and modified as necessary Install crane, clean room, and other infrastructure in 2008 Bring experimental apparatus in 2009 Key question is how best to modularize for transport, installation

27 Early Access to SNOLAB for R&D Radon monitoring Want periodic, long-term measurements (detect seasonal spikes) Study of Radon deposition on various materials in situ Probably want a small underground clean room or bench Neutron measurements Specifically interested in flux of fast neutrons from fissions, (alpha,n) Low-Background counting plans for SNOLAB Plans for common equipment and counting area

28 Summary Broad consensus that the science goals of the SuperCDMS 25 kg Experiment are exciting and timely. P5 and HEPAP recommend construction start in FY2008. We have already demonstrated our technology works for one-inch-thick detectors, and we are proceeding to full verifications of rejection factors over the next few years. Our plan for a new experiment at the deeper SNOLAB site is the best strategy to maximize the science reach, reduce the technical risk and backgrounds, and enhance the probability for a timely and high-confidence discovery. The combination of finishing the Soudan phase of CDMS and SuperCDMS 25 kg at SNOLAB should achieve x100 better sensitivity to WIMP dark matter. The discovery potential is high. We look forward to working with SNOLAB to make SuperCDMS a reality!