1. Path Towards A Large Scale Ilan Levine Indiana University South Bend For the PICASSO collaboration Detector Workshop on Next Generation Dark Matter Detectors University of Chicago, Chicago, 9-10 December, 2004

2. E. Behnke, W. Feighery, M. Henderson, I. Levine, C. Muthusi, L. Sawle Indiana University South Bend, South Bend, IN, USA G. Azuelos, M. Bernabé-Heider, M. Di Marco, P Doane, M.H. Genest, R. Gornea, R. Gu é nette, C. Leroy, L. Lessard, J.P. Martin, U. Wichoski, V. Zacek Université de Montréal, Montréal, Canada S. N. Shore, Dipartimento di Fisica Università di Pisa, Pisa, Italy K. Clark, C. Krauss, A.J. Noble Queens University, Kingston, ON, Canada R. Noulty, S. Kalanalingam Bubble Technology Industries, Chalk River, ON, Canada F. d’Errico Yale University Medical School, New Haven, CT, USA Collaboration agreements signed with: France, Portugal + Czech Republic + …..

3. Metastable Superheated Freon droplet, suspended in gel Adjust pressure (and superheat) WIMP/ 19 F elastic scatter Recoiling 19 F creates microscopic vapour cavities. If R cavity >R ”critical”, Phase transition irreversible. ~Half thermal PE released acoustically Freon bubble Freon bubble Acoustic sensor, preamp, daq Temp Control

4. 2000 Exposure 106 g *d Overburden: 6.7m rock 2004 Exposure ~1 kg *d Overburden: 2000m rock ~500 cts/d/kg  contamination 2005 Exposure ~140 kg *d 200 cts/d/kg  contamination Exposure ~1400 kg *d 20 cts/d/kg  contamination Exposure ~14000 kg *d 0.2 cts/d/kg  contamination

5. Changing and measuring T Gel Composition –Minimize repressure time –Life –Radiopurity –PICASSO/SIMPLE/ E.-G. Total Active Target Edge effects Dissolved gas effects Containers

6. C [cts/gram x neutron/cm 2 ] 5014 n-beam/ Microsc. DF68 Cb24 MC 4437 n-beam/ Microsc. DF37 Cb26 Cb27 Cb28 Mb29 Determination of Active Mass Average: C=0.110  0.005 cts/g n cm -2 (  2 red = 1.5) Four different methods give consistent result! 1)Microscope 2)Calibr. neutron - beam 3)Weighting 4)Simulation of response 1 2 1 2 2 2 2 4 23

7. 8ml ~1 L SNO polypro. 8g/detector 4.5 L Acrylic 40g/detector Evolution of containers: Larger & Cleaner

8. Non-WIMP induced transition –Cosmic ray related –Local radioactivity sources –Internal radio-contamination, LET(&RET?), recoil threshold function Target:Pb or I doping to enhance coherent X-sect.? Calibration of larger detectors (30L)

9. Metallic components, unpurif. CsCl: 30 cts/g/d Purified CsCl: 2.5 cts/g/d Background Evolution of 1l Detectors  Purification & fabrication in UdeM clean room  no metals in contact with solution  non-metallic lid during fabrication  CsCl & other gel ingredients cleaned with HTiO  Freon distilled

10. Status: 3 rd generation (Cleanroom) Alpha – particle background 2 nd generation Data taking at SNO Neutralino  =5 pb, 50GeV

11. 40 o 5 o 25 o BD 100 T( o C): Nuclear recoils  - particles  -recoils ,  Mips  -electrons « Foam limit  = 50% 1 MeV 100 keV 1 keV 10 eV BD 1000 T( o C): 30 o 45 o 60 o (neutron calibrations)  = 90%

12. Detector Response & Calibration  SBD’s are threshold detectors!  Calibration of energy response with monochromatic neutrons from 7 Li(p,n) reaction dN/dE REC 30 20 10E REC (keV) F E n = 100keV E TH (45 0 )E TH (35 0 ) Measurements at 5 MeV UdeM tandem accelerator

13. Acoustic Attenuation Geometrical dependences Submergible sensors Signal/Noise Other signals of transition? (Cherenkov? Scintillator?) Trigger criteria at high superheat Thickness mode Piezo element All data (bubbles, doors, internet, cell phone, coughs!) Only bubbles

15. Temperature [ o C] Filter acceptance: Raw /passed events Acceptance

16. False phase transitions –Electronic noise –Environmental signals (e.g. blasting) –Decompression events –Event 3-D localization

17. Digital filter Digital Filtering of the data

18. Formalize Analysis –“Blind” Analysis –Separate analysis teams Extend MC model (shielding, external MIPS, etc) Collaboration Growth (10kg detector and beyond) and phased plan.

19. Monte Carlo Simulation of Detector Response  GEANT 4 V4.5.2 ½  Neutron code ENDF/B  nuclear stopping power model ICRU_ R49  electronic stopping power model SRIM 2000p Input:  Detector loading  droplet size distribution  E min (T), P(E, E th ) 400 keV neutrons

20. The Future in Three Phases: Phase 1: reach DAMA Phase 2: reach tip of MSSM predictions Phase 3: reach core of MSSM predictions Active mass Back- ground Location at SNO Start data taking End data taking RuntimeExposureLimits (pb) 40 g200 cts/kg/d D 2 0 tank15.04.0415.10.044 months3 kgd 0.5 pb 1 kg200 cts/kg/d D 2 0 tank01.12.0401.06.056 months140 kgd0.07 pb 3 kg20 cts/kg/d D 2 0 tank01.06.0501.12.056 months420 kgd1x 10 -2 pb 10 kg20 cts/kg/d Lunch room 01.12.0501.06.066 months1400 kgd7x10 -3 pb 10 kg2 cts/kg/dLunch room 01.06.0601.12.066 months1400 kgd2x10 -3 pb 100 kg0.2 cts/kg/d New cavity in SNOLAB 01.05.0701.11.076 months14000 kgd2 x10 -4 pb

21. Check entire DAMA region in 2005! Conclusions R&D new modules 3 –30 litres Growth of collaboration: Univ. de Paris & Univ. Di Lisboa (SIMPLE) Czech Tech. U. of Prague, Yale, BTI Phased growth of detector and techniques to enter MSSM phase space soon. Most covered before 2010. Excellent rating of LOI (including phased approach) by Exp. Advisory Commitee. Next stage is full proposal for large scale detector