SIMPLE Tom Girard for the SIMPLE Collaboration SIMPLE
SIMPLE Tom Girard ( for the SIMPLE Collaboration )
SIMPLE WIMP Superheated freon droplet gas 25 m 1 mm ( Seitz : Phys. Fluids 1 (1979) 1 ) (i) E > Ec = 4 prc 2 g/3 e E/ x 150 ke. V/μm (ii) E/ x > Ec/arc • key feature: selective sensitivity tunable (P, T) double threshold device intrinsic BG rejection < 10 -10 v-a-v bolometers: 10 -4, -5 xenon: 10 -2 argon: 10 -7, -8
Instrumentation MCE-200 microphone PGA 2500 adaptive amplifier true nucleation event noise: 2 -3 m. V Δ : 1. 6 x 10 -2 ms ΔV: 0. 3 m. V 1 TB pcs (8 chl each), Mat. Lab files of ~ 8 min (~ 4 MB) each SDD
Laboratoire Souterrain a Bas Bruit [LSBB]
GESA ( 60 m 3) 30 -100 cm thick concrete 50 -75 cm thick water (shield, pool) 20 cm thick wood 1 cm thick steel 50 cm thick concrete (floor) atmospheric radon: 20 – 3000 Bq/m 3 reduction : • ventilation 10 x per day • top-circulation of waterpool (25 liter/min)
GESA backgrounds neutron : muon : 8. 6 x 102 m-2 d-1 232 Th concrete steel water (Bq/kg) 7. 7 0. 02 7 x 10 -5 ( , n) + sf + ( , n) 238 U (Bq/kg) 11 1. 8 10 -4 40 K (Bq/kg) 57 0. 02 -- shielding 1. 09 ± 0. 02 ± 0. 07 evt/kgd : water circulation ( 25 l/min ) radon : air internal: < 0. 71 evt/kgd (radioassay) 0. 36 Bq/m 3 diffusion 0. 0012 Bq/m 3 3. 26 ± 0. 08 ± 0. 76 evt/kgd
Phase II Ø stage I : 14. 095 kgd ( arxiv: 1003. 2987 v 2 [astro-ph. CO] 22 Mar 2010 ) Ø 27 October -- 14 November 2009 : SDD installation, 1 per day ( +1. 9 kgd ) Ø 15 November 2009 – 05 February 2010 ( 12. 2 kgd ) • data losses ( -4. 70 kgd ) due to weather-induced power failures Ø stage II : ~18 kgd Ø 12 April – 01 May 2010: SDD installation, 1 per day ( +1. 9 kgd ) Ø 02 May – 22 July 2010: full complement ( +15. 6 kgd ) • no data losses
Signal analysis protocol: Ø accept all signals with amplitude > 2 m. V over SDD noise (4056) ( efficiency 0. 97 with 95% CL or better ) Ø remove 2228 coincident signals ( efficiency 0. 99 with 99% CL ) Ø freon-less SDD Ø any other SDD Ø filter remaining 1828 signals wrt Ø signal waveform (amplitude, decay constant, . . . ) Ø FFT structure (frequency, intensity distribution. . . )
Acoustics = ? ? internal external Ø gel fractures (81 evt) Ø water inlet bubbles (40%) Ø N 2 release (63) Ø SDD deck motion (15%) Ø N 2 escape (4%) Ø electronic noise (5%) Ø gel deterioration (10%) Ø SDD “Papa” noise (10%) Ø. . Ø human noise (5%) Ø. . NONE possess signal parameters or FFTs of true nucleation events identification efficiency 97% at 95% CL
“MOST Wanted” Gallery ventilation human noise fracture true water bubbles pressure release trapped N 2 gas Fenwick motion cap knocking microleak
RESULTS : 1828 evts total => 60 true nucleation events “true” : = 450 -750 Hz = 5 -40 ms
neutron and calibrations sound detection efficiency : 0. 98 ± 0. 03 Erth (9ºC) = 8. 0 ± 0. 1 ke. V 3. 26 ± 0. 48 evt/kgd consistent with sub-water radon level, SDD radiopurity ( acceptance 0. 97 ) 0. 99 ± 0. 28 evt/kgd consistent with MCNP 1. 09 ± 0. 02 ± 0. 07 evt/kgd based on material radio-assays
low amplitude sector = neutrons + WIMPS How many WIMPs possible ? neutrons observed : [14 ± 3. 8 ] x (1/0. 98) x (1/0. 97) = 14. 7 ± 4. 0 evt neutrons estimated: 14. 1 x [1. 09 ± 0. 02 ± 0. 07] = 15. 4 ± 0. 28 ± 0. 99 evt so Ø simple diff = -0. 70 ± 4. 1 evts Ø more conservative : ( max observed – min estimated ) evts expected ( [14. 7 + 4. 0] – [15. 4 – 1. 0] ) = 4. 3 evt => up to 8 expected WIMPs at 90% CL
SD RESULTS (stage I) SD ~ [ ap<Sp> + an<Sn> ]2 J-1(J+1) <Sp> = 0. 441 ; <Sn> = -0. 109
SI RESULTS (stage I)
status & prospects Ø 14. 1 kgd completed ( 27/10 – 05/02, losses) > with XENON 10, ~ 50% reduction in allowed SD phase space Ø + 18 kgd completed ( 01/05 – 22/07, no losses) – under analysis > reduce background subtraction : > less neutrons : xtra 10 cm wood, PE below waterpool 0. 2 n / kgd > additional radio-assays of shielding, tank water. . . > prob’ly more ’s (Summer radon 1000 Bq / m 3) > further refinements in signal analysis (hi-frequency component)
signal amplitudes only this region capable of providing nucleation d. E/dx neutron “big bang” “bang” N d. E/dx temperature (ºC) droplet diameter ( m)
xtra
SI rate : ar. Xiv: astro-ph/0703543 ~ A 2 but there’s also F 2,
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