Path Towards A Large Scale

Ilan LevineIndiana University South Bend For the PICASSO collaboration

Detector

Workshop on Next Generation Dark Matter Detectors

University of Chicago, Chicago, 9-10 December, 2004

E. Behnke, W. Feighery, M. Henderson, I. Levine, C. Muthusi, L. SawleIndiana University South Bend, South Bend, IN, USA

G. Azuelos, M. Bernabé-Heider, M. Di Marco, P Doane, M.H. Genest, R. Gornea, R. Guénette, C. Leroy, L. Lessard, J.P. Martin, U. Wichoski, V. ZacekUniversité de Montréal, Montréal, Canada

S. N. Shore, Dipartimento di FisicaUniversità di Pisa, Pisa, Italy

K. Clark, C. Krauss, A.J. NobleQueens University, Kingston, ON, Canada

R. Noulty, S. KalanalingamBubble Technology Industries, Chalk River, ON, Canada

F. d’ErricoYale University Medical School, New Haven, CT, USA

Collaboration agreements signed with: France, Portugal + Czech Republic + …..

Metastable SuperheatedFreon droplet,suspended in gel

Adjust pressure (and superheat)

WIMP/19F elastic scatter

Recoiling 19F creates microscopic vapour cavities. If Rcavity>R ”critical”, Phase transition irreversible. ~Half thermal PE released acoustically

Freonbubble

Freonbubble Acoustic

sensor, preamp, daq

Temp Control

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

• Changing and measuring T

• Gel Composition – Minimize repressure time– Life– Radiopurity– PICASSO/SIMPLE/ E.-G.

• Total Active Target

• Edge effects

• Dissolved gas effects

• Containers

C [

cts/

gram

x n

eutr

on/c

m2 ]

5014n-beam/Microsc.

DF68

Cb24

MC

4437n-beam/Microsc.

DF37

Cb26

Cb27

Cb28 Mb29

Determination of Active Mass

Average: C=0.1100.005 cts/g n cm-2

(2red = 1.5)

Four different methods give consistent result!

1) Microscope

2) Calibr. neutron - beam

3) Weighting

4) Simulation of response

1

2

12

2 2

2

4

2 3

8ml

~1 L

SNO polypro.8g/detector

4.5 L

Acrylic40g/detector

Evolution of containers: Larger & Cleaner

• 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)

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

Status:

3rd generation

(Cleanroom)

Alpha – particle background

2nd generation

Data taking at SNO

Neutralino =5 pb, 50GeV

40o 5o 25oBD 100 T(oC):

Nuclear recoils

- particles

-recoils

,

Mips

-electrons

« Foam limit

= 50% 1 MeV

100 keV

1 keV

10 eV

BD 1000 T(oC): 30o 45o 60o

(neutron calibrations)

= 90%

Detector Response & Calibration

SBD’s are threshold detectors!

Calibration of energy response with

monochromatic neutrons from 7Li(p,n) reaction

dN

/dE

RE

C

302010 EREC (keV)

F En = 100keV

ETH(450) ETH(350)

Measurements at 5 MeV UdeM tandem accelerator

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25

Source distance(cm)

#ev

en

ts

• 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

Temperature [oC]

Filter acceptance: Raw /passed eventsA

ccep

tanc

e

• False phase transitions

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

Digital filter

Digital Filtering of the data

• Formalize Analysis– “Blind” Analysis– Separate analysis teams

• Extend MC model (shielding, external MIPS, etc)

• Collaboration Growth (10kg detector and beyond) and phased plan.

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

Emin(T), P(E, Eth)

400 keV neutrons

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

Runtime Exposure Limits (pb)

40 g 200 cts/kg/d

D20 tank 15.04.04 15.10.04 4 months 3 kgd 0.5 pb

1 kg 200cts/kg/d

D20 tank 01.12.04 01.06.05 6 months 140 kgd 0.07 pb

3 kg 20 cts/kg/d

D20 tank 01.06.05 01.12.05 6 months 420 kgd 1x 10-2 pb

10 kg 20cts/kg/d

Lunch room

01.12.05 01.06.06 6 months 1400 kgd 7x10-3 pb

10 kg 2 cts/kg/d Lunch room

01.06.06 01.12.06 6 months 1400 kgd 2x10-3 pb

100 kg 0.2cts/kg/d

New cavity in SNOLAB

01.05.07 01.11.07 6 months 14000 kgd 2 x10-4 pb

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