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SNOLAB WORKSHOP OCT. 4 2008 V. Zacek Université de Montréal

Project overview Progress report Milestones and Schedule Infrastructure needs Personnel & HQP Outlook. SNOLAB WORKSHOP OCT. 4 2008 V. Zacek Université de Montréal.

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SNOLAB WORKSHOP OCT. 4 2008 V. Zacek Université de Montréal

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  1. Project overview • Progress report • Milestones and Schedule • Infrastructure needs • Personnel & HQP • Outlook SNOLAB WORKSHOP OCT. 4 2008 V. Zacek Université de Montréal

  2. Université de Montréal, Queen’s University, University of Alberta, Laurentian University, University of Indiana, South Bend, SNOLAB, CTU Prague, Bubble Technology Industries

  3. Isotope Spin Unpaired 2 7Li 3/2 p 0.11 19F 1/2 p 0.863 23Na 3/2 p 0.011 29Si 1/2 n 0.084 73Ge 9/2 n 0.0026 127I 5/2 p 0.0026 131Xe 3/2 n 0.0147 Active Target C4F10 Neutralino interaction with matter: Enhancement factor Spin independent interaction (CA A2 ) Spin dependent interaction Depending on the type of target nucleus and neutralino composition CA = (8/)(ap<Sp>+ an<Sn>)2(J+1)/J  Spin of the nucleus is approximately the spin of the unpaired proton or neutron

  4. Comparison SD and SI - searches • no channel favoured • largely uncorrelated • destructive interference possible in SI sector Need to explore both sectors!

  5. Spin Dependent Sector (TAUP ’07) KIMS: 3403 kgd NAIAD: 12523 kgd PICASSO: 22 kgd SM predictions O(10-3 pb)

  6. Superheated droplets at ambient T & P * • 150m droplets of carbofluorides dispersed in polymerised gel • Active liquid: C4F10 Tb= - 1.7 oC) • Radiation triggers phase transition • Events recorded by piezo-electric transducers * Inspired by personal neutron dosimeters @ Bubble Technology Industries, ON

  7. Main Features • - each droplet is an independent “clean” Bubble Chamber • keV threshold for DM induced recoils • with full efficiency for nuclear recoils • excellent gamma & MIP at Erec= 5 keV • continuous operation 30h • recompression recycles burst droplets • low cost, with potential for a large DM experiment • in house fabrication 1st generation: 10 mL 2nd generation : 1L 3rd generation : 4.5L

  8. Detector Response 226Ra spike (200 m Ø)

  9. Detector Response 226Ra spike (200 m Ø) AcBe neutrons (data +MC)

  10. Detector Response 226Ra spike (200 m Ø) Recoil nuclei from 50 GeV WIMP AcBe neutrons (data +MC)

  11. Detector Response 226Ra spike (200 m Ø) Reoil nuclei from 50 GeV WIMP AcBe neutrons (data +MC)  & MIP response Gamma & MIP rejection better 1010above Erec= 10keV!

  12. 2.6 kg PHASE • 32 detectors  2.6 kg of C4F10 • 288 acoustic R/O channels • 3D event localization • 20 detectors running • another 8 detectors u/g ; 4 ready @ UdeM to ship • analysis in progress • publication of intermediary results in prep. • Critical item at the moment: ADC boards! • 20 / 32 installed • 4 more ready; 8 to be debugged (soldering accident)

  13. Temperature & Pressure Control System (TPCS) • - TPCS units • temp. precision: ± 0.10C • - 4 detectors /TPCS • - 40 h data taking • - 15 h recompression

  14. Data Analysis • filter events (high pass) • Integrate Ampl.2 • time frequency analyis • spike cuts Compare to known backgrounds  Limits @90%C.L.

  15. Sensitivity (22 kgd ) PRELIMINARY

  16. Timeline & Milestones 700 kgd 0.06 pb* 700 kgd 0.006 pb 7000 kgd 0.002 pb * Present background of 0.003 cts g-1h-1

  17. Scientific Reach 2.6 kg Phase (ongoing) 700 kgd Bckg 0.003 cts h-1g-1 2.6 kg* 700 kgd Bckg: 3x10-5 cts h-1g-1 MSSM 25 kg Phase 000 kgd 30L modules Backg.: 3x10-5 cts h-1g-1 Spin Dependent Sector

  18. Infrastructure needs • On site support extremely helpful (I. Lawson) •  short interventions, change electronics, assistance before/ after power outages • Access @ measuring time at HP(Ge) •  regular assays of samples || to detector fabrication • Office space / cubicles •  with full installation c.o.g. shifting to SNOLAB • Radiochemistry and low background expertise •  SNOLAB (Laurentian) radio chemistry lab for spike work • Electronics maintenance support from technician (Reg, Noël) • Computing support for on-line servers and network • Clean lab space for sample preparation

  19. Discrimination of Nuclear Recoils from Alpha Particles PICASSO discovered a significant difference between amplitudes of neutron and - particle induced events !Accepted for pub. In New Journal of Physics arXive: 0807.1536 n-calibration - background Average of peak amplitudes of nine transducers / detector High pass filter with cut-off at 15 KHz Signals carry information about first moment of bubble formation

  20. Discrimination of Nuclear Recoils from Alpha Particles PICASSO discovered a significant difference in amplitudes between neutron and  - particle induced events !Accepted for pub. In New Journal of Physics arXive: 0807.1536 Are these really  events?  -like Temperature response! Signals carry information about first moment of bubble formation

  21. Discrimination of Nuclear Recoils from Alpha Particles PICASSO discovered a significant difference between amplitudes of neutron and - particle induced events !Accepted for pub. In New Journal of Physics arXive: 0807.1536 Why not observed earlier? • Previous detector had smaller droplets! • now 200 m compared to < 10 m • range of nuclear recoils < Lc • but range of alphas >> Lc • many bubbles can form on  track (depend on temperature)

  22.  - n Discrimination: a tentative explanation Nuclear recoil: point like, strong ionisation # of primary bubbles 1 • -particles: ionization on 35m track  # prim. bubbles Poisson distributed ! Lc <> = 1 T = 300C <> = 4 T = 400C Lc <> = 8 T = 500C Lc # of bubbles created (in MIP sensitive region: T = 600C > 20 bubbles)

  23.  - n Discrimination: Temperature Dependence Strong saturation of raw signals above 300C!

  24.  - n Discrimination: Discussion • From bubble chamber operation: •  bubble density  dE/dx  •  bubble density strongly increases with T  • Plesset-Zwick theory: •  bubble growth  •  pressure amplitude  acceleration & temperature •  first 50s of signal preserve m resolution of prim. event • increase discrimination by controlling gain  new pulser • increase resolution by using 3D info • eliminate saturation effects by reducing gain • run at one temperature only ! (450?) Next: Very exciting!

  25. Detector Fabrication • Well organized, timed and rapid! • Chain production of 3 –4 detectors / working day • Large droplets ( 200 m Ø) • CsCl loaded matrix replaced by hydrocarbon based version •  intrinsically much cleaner in U/Th !! •  performance issues under investigation Ultra Pure Water system (18.2 MΩ ⇔ 0.2ppb)

  26. 3. Determination of Droplet Size (L.U.) Tracing the droplets 2400 droplets gel sample: 0.7 mL Imaging the sample Droplet size distribution (volume) • Analyze gel from more detectors and compare • Continue development of nondestructive method

  27. Progress in Test Beam Calibration • Calibration with mono-energetic neutrons • neutron induced nuclear recoils similar to WIMPS • n-p reactions on 7Li and 51V targets at 6 MV UdeM-Tandem • threshold measurements in the sev. keV region Detection efficiency (T) Neutralino response (T)

  28. Target selection Lithium (7Li) Previous measurements: 7Li target 200 keV < En < 5000 keV. Vanadium (51V) 528 keV 40 keV New measurements: 51V target 5 keV < En < 90 KeV

  29. Check of resonance in V-target Five 51V resonances: 97, 61, 50, 40 and 5 keV

  30. Improved Calibration of the Detector Response 51V resonances 7Li data Theory

  31. Monte Carlo Simulations Test beam AmBe source (u/g calib.) • Response at threshold not a step function! •  - increases with neutron energy! New!

  32. COLLABORATION DEMOGRAPHY • Present compostion • MSc students: 5 • PhD students: 1 • Ugrad. lab students 2 (IUSB) • Postdocs: 3 • Researchers and faculty: 10 (4 FTE) • Engineers (electr.) 1 • Technicians 4 • Careers & Training: • completed MSc theses: 11 (4 in ’08) • completed PhD theses: 4 (2 in ’08) • RA  faculty: 2 U. Wichoski (UdeM  L.U.) C. Krauss (Q.U.  U.A.) • > 30 summer students during the last six years • > 6 “stage” students from France (région Rhône Alpes)

  33. Distribution of Tasks • Montréal: - electronics, DAQ, analysis • - detector fabrication + R&D • - calibration, quality control • Queen’s: - slow control (T&P), u/g install. + coordination • - on-line monitoring, DAQ, analysis • - detector fabrication, purification +R&D • Alberta: - slow control, u/g install., electronics • - analysis + coordination • Laurentian: - det. characterization, purification, u/g install. • SNOLAB: - HP(Ge) assays, on-site support (I. Lawson) • Indiana: - piezo transducer fabrication, quality control • Prague: - detector container fabrication / Monte Carlo

  34. PICASSO - COUPP - MOU

  35. PICASSO/COUPP  Joint Strategy for 100kg Detector? SD SI PICASSO / COUPP eventually also SI interactions?

  36. Summary • 2.6 kg Phase with 32 detectors nearly completed • 20 of 32 detectors installed; 28 u/g; 31 modules ready • Upgrade gradually with cleaner detectors “saltless” detectors • New discovery of n -  discrimination • Physics results to be published soon • Complete Phase 1 with 700 kgd in 2009 • R&D on purification (1/100) and 30L detectors • prepare 25 kg phase  7000 kgd

  37. Superheated Liquids For Particle Detection 1952 Donald Glaser: “Some Effects of Ionizing Radiation on the Formation of Bubbles in Liquids” (Phys. Rev. 87, 4, 1952) 1958 G. Brautti, M. Crescia and P. Bassi: “A Bubble Chamber Detector for Weak Radioactivity” ( Il Nuovo Cimento, 10, 6, 1958) 1960 B. Hahn and S. Spadavecchia “Application of the Bubble Chamber Technique to detect Fission Fragments” (Il Nuovo Cimento 54B, 101, 1968) 1993 “Search for Dark Matter with Moderately Superheated Liquids” (V.Z., Il Nuovo Cimento, 107, 2, 1994) Superheated Liquids & Dark Matter: SIMPLE, COUPP, PICASSO

  38. Detector Response  MIPS neutrons WIMPS

  39. Detector Response B. Hahn, Il Nuovo Cimento, 1961, Vol. 22, 650

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