SNOLAB WORKSHOP OCT. 4 2008 V. Zacek Université de Montréal
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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
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Université de Montréal, Queen’s University, University of Alberta, Laurentian University, University of Indiana, South Bend, SNOLAB, CTU Prague, Bubble Technology Industries
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AA
AFA C
MM
MMG
2
24
Enhancement factor
Neutralino interaction with matter:
Depending on the type of target nucleusand neutralino composition
Spin independent interaction (CA A2 )
Spin dependent interaction
CA = (8/)(ap<Sp>+ an<Sn>)2(J+1)/J
0.0147n3/2131Xe
0.0026p5/2127I
0.084n1/229Si
0.0026n9/273Ge
0.011p3/223Na
0.863p1/219F
0.11p3/27Li
2UnpairedSpinIsotope
Spin of the nucleus is approximately the spinof the unpaired proton or neutron
Active Target C4F10
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Comparison SD and SI - searches
• no channel favoured
• largely uncorrelated
• destructive interference possible in SI sector
Need to explore both sectors!
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Spin Dependent Sector (TAUP ’07)
KIMS: 3403 kgd
NAIAD: 12523 kgd
PICASSO: 22 kgd
SM predictions O(10-3 pb)
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Superheated droplets at ambient T & P *
150m 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
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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
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Detector Response
226Ra spike (200 m Ø)
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Detector Response
226Ra spike (200 m Ø)
AcBe neutrons (data +MC)
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Detector Response
226Ra spike (200 m Ø)
AcBe neutrons (data +MC)
Recoil nuclei from 50 GeV WIMP
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Detector Response
Gamma & MIP rejection better 1010 above Erec= 10keV!
226Ra spike (200 m Ø)
AcBe neutrons (data +MC)
Reoil nuclei from 50 GeV WIMP
& MIP response
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2.6 kg PHASE
Critical item at the moment: ADC boards!
• 20 / 32 installed
• 4 more ready; 8 to be debugged (soldering accident)
• 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.
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Temperature & Pressure Control System (TPCS)
- TPCS units
- temp. precision: ± 0.10C
- 4 detectors /TPCS
- 40 h data taking
- 15 h recompression
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Data Analysis
• filter events (high pass)
• Integrate Ampl.2
• time frequency analyis
• spike cuts
Compare to known backgrounds Limits @90%C.L.
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Sensitivity (22 kgd )
PRELIMINARY
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’07 ’08 ’09 ’10 ’11
2.6 kg 32 modules
Data taking 8 –16 modules
Data taking 20 modules
Preamps, DAQ boards
Installation + 12 modules
Data taking 32 modules
R&D backg. /100
2.6 kg* (backg./100)
Data taking 32 modules
R&D 30L mod. high ldg.
Phase II 25 kg
30L detector prod.
Data taking Ladder Lab ?
Timeline & Milestones
700 kgd
7000 kgd
* Present background of 0.003 cts g-1h-1
700 kgd
0.002 pb
0.006 pb
0.06 pb*
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Scientific Reach
2.6 kg Phase (ongoing)700 kgdBckg 0.003 cts h-1g-1 2.6 kg*
700 kgdBckg: 3x10-5 cts h-1g-1
25 kg Phase 000 kgd 30L modulesBackg.: 3x10-5 cts h-1g-1
Spin Dependent Sector
MSSM
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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
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Discrimination of Nuclear Recoils from Alpha Particles
Average of peak amplitudes of nine transducers / detector
High pass filter with cut-off at 15 KHz
PICASSO discovered a significant difference between amplitudes of neutron and - particle induced events ! Accepted for pub. In New Journal of Physics arXive: 0807.1536
Signals carry information about first moment of bubble
formation
n-calibration - background
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Discrimination of Nuclear Recoils from Alpha Particles
Are these really events?
PICASSO discovered a significant difference in amplitudes between neutron and
- particle induced events ! Accepted for pub. In New Journal of Physics arXive: 0807.1536
Signals carry information about first moment of bubble
formation
-like Temperature response!
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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)
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Nuclear recoil: point like, strong ionisation
-particles: ionization on 35m track
# prim. bubbles Poisson distributed !
- n Discrimination: a tentative explanation
# of primary bubbles
<> = 1
<> = 4
<> = 8
# of bubbles created
T = 300C
T = 400C
T = 500C
Lc
Lc
Lc
(in MIP sensitive region: T = 600 C > 20 bubbles)
1
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- n Discrimination: Temperature Dependence
Strong saturation of raw signals above 300C!
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• From bubble chamber operation:
bubble density dE/dx
bubble density strongly increases with T
• Plesset-Zwick theory:
bubble growth
pressure amplitude acceleration & temperature
first 50s of signal preserve m resolution of prim. event
t
- n Discrimination: Discussion
Next: • 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?)
Very exciting!
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Ultra Pure Water system (18.2 MΩ ⇔ 0.2ppb)
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
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3.
Imaging the sample
Determination of Droplet Size (L.U.)
Tracing the droplets
Droplet size distribution (volume)
2400 droplets
gel sample: 0.7 mL
• Analyze gel from more detectors and compare
• Continue development of nondestructive method
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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
Progress in Test Beam Calibration
Detection efficiency (T) Neutralino response (T)
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Lithium (7Li)
Vanadium (51V)528 keV
40 keV
Previous measurements: 7Li target
200 keV < En < 5000 keV.
New measurements: 51V target
5 keV < En < 90 KeV
Target selection
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Check of resonance in V-target
Five 51V resonances:
97, 61, 50, 40 and 5 keV
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Improved Calibration of the Detector Response
51V resonances
7Li data
Theory
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Monte Carlo Simulations
• Response at threshold not a step function!
• - increases with neutron energy!
)1(exp1),(th
th EEEEP
Test beam
New!
AmBe source (u/g calib.)
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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)
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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
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PICASSO - COUPP - MOU
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SD
SI
PICASSO/COUPP Joint Strategy for 100kg Detector?
PICASSO / COUPP eventually also SI interactions?
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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
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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 For Particle Detection
Superheated Liquids & Dark Matter: SIMPLE, COUPP, PICASSO
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Detector Response
neutrons
WIMPS
MIPS
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Detector Response
B. Hahn, Il Nuovo Cimento, 1961, Vol. 22, 650