Post on 05-Jan-2016
SIMPLETom Girard
( for the SIMPLE Collaboration )
SIMPLE
gas
25 m 1 mm
WIMP
Superheatedfreon droplet
(i) E > Ec = 4rc2/3
(ii) E/x > Ec/arc
( Seitz : Phys. Fluids 1 (1979) 1 )
E/ x 150 keV/μm
intrinsic BG rejection < 10-10 v-a-v
bolometers: 10-4,-5
xenon: 10-2
argon: 10-7,-8
• key feature: selective sensitivity
tunable (P,T) double threshold device
Instrumentation
MCE-200microphone
true nucleation event
PGA2500adaptive amplifier
1 TB pcs (8 chl each), MatLab files of ~ 8 min
(~ 4 MB) each SDD
noise: 2-3 mV
Δ : 1.6 x10-2 ms
ΔV: 0.3 mV
Laboratoire Souterrain a Bas Bruit [LSBB]
GESA ( 60 m3)
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/m3
reduction : • ventilation 10x per day
• top-circulation of waterpool (25 liter/min)
GESA backgrounds
232Th (Bq/kg) 238U (Bq/kg) 40K (Bq/kg)
concrete 7.7 11 57steel 0.02 1. 8 0.02water 7x10-5 10-4 --
1.09 ± 0.02 ± 0.07 evt/kgd
neutron :
:
radon : air 0.36 Bq/m3 0.0012 Bq/m3
internal: < 0.71 evt/kgd (radioassay)
water circulation ( 25 l/min ) diffusion
(,n) + sf + (,n) shielding
muon : 8.6 x 102 m-2d-1
3.26 ± 0.08 ± 0.76 evt/kgd
stage I : 14.095 kgd ( arxiv:1003.2987v2 [astro-ph.CO] 22 Mar 2010 )
27 October -- 14 November 2009 : SDD installation, 1 per day ( +1.9 kgd )
15 November 2009 – 05 February 2010 ( 12.2 kgd )
• data losses ( -4.70 kgd ) due to weather-induced power failures
stage II : ~18 kgd
12 April – 01 May 2010: SDD installation, 1 per day ( +1.9 kgd )
02 May – 22 July 2010: full complement ( +15.6 kgd )
• no data losses
Phase II
Signal analysis protocol:
accept all signals with amplitude > 2 mV over SDD noise (4056) ( efficiency 0.97 with 95% CL or better )
remove 2228 coincident signals ( efficiency 0.99 with 99% CL )
freon-less SDD
any other SDD
filter remaining 1828 signals wrt
signal waveform (amplitude, decay constant,...)
FFT structure (frequency, intensity distribution...)
Acoustics = ??
water inlet bubbles (40%)
SDD deck motion (15%)
electronic noise (5%)
SDD “Papa” noise (10%)
human noise (5%) ....
NONE possess signal parameters or FFTs of true nucleation events
identification efficiency 97% at 95% CL
gel fractures (81 evt)
N2 release (63)
N2 escape (4%)
gel deterioration (10%) ....
internal external
“MOST Wanted” Gallery
ventilation
cap knockinghuman noise pressure release
water bubbles Fenwick motion
microleakfracture trapped N2 gas
true
RESULTS : 1828 evts total => 60 true nucleation events
0 150 300 450 600 750 900 1050 1200 1350 1500
0
100
200
300
400
500
600
700
0
100
200
300
400
500
600
700
Am
plitu
de
(mV
)
(
ms)
Frequency (Hz)
true nucleation (1.5%) gel fracture (2.0%) acoustic (54.9%) N
2 release (1.6%)
false nucleation (0.5%)
“true” : = 450-750 Hz = 5-40 ms
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 170,0
0,2
0,4
0,6
0,8
1,0
1,2 n calibrations (Am/Be) calibrations (U308)
norm
aliz
ed e
ven
t n
umbe
r
ln (A2)
450 500 550 600 650 700 750 800 850 900 950
102
103
104
105
106
107
n calibration calibration run (n) run ()
am
plit
ud
e2 (
mV
2)
frequency (Hz)
neutron and calibrations
3.26 ± 0.48 evt/kgd
consistent with sub-water radon level, SDD radiopurity
0.99 ± 0.28 evt/kgd
consistent with MCNP 1.09 ± 0.02 ± 0.07 evt/kgd
based on material radio-assays
sound detection efficiency : 0.98 ± 0.03 Erth (9ºC) = 8.0 ± 0.1 keV
( acceptance 0.97 )
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
simple diff = -0.70 ± 4.1 evts
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
-2,0 -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5 2,0-2
-1
0
1
2
KIMS (3.9 ky)
COUPP (52 kgd)
PICASSO (14 kgd)
SIMPLE (14 kgd)
XENON10 (136 kgd)
NAIAD (16k kgd)
CDMS-II (121 kgd)
ap
an
ZEPLIN-III (127 kgd)
MW = 50 GeV/c2
DAMA/LIBRA
SD RESULTS (stage I)SD ~ [ ap<Sp> + an<Sn> ]2 J-1(J+1)
<Sp> = 0.441 ; <Sn> = -0.109
10 100 10001E-8
1E-7
1E-6
1E-5
1E-4
SIMPLE (14 kgd)
CRESST-II(67 kgd)
WARP(97 kgd)
KIMS(3.9 kgy)
COUPP(52 kgd)
EDELWEISS(144 kgd)
XENON10(136 kgd)
NAIAD(16k kgd)
CDMS-II(195 kgd)
ZEPLIN-III(127 kgd)
S
I
N (
pb)
MW
(GeV/c2)
SI RESULTS (stage I) max
min
v
v
22 dvv
)v(fFA~
status & prospects
14.1 kgd completed ( 27/10 – 05/02, losses)
> with XENON10, ~ 50% reduction in allowed SD phase space
+ 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 / m3)
> further refinements in signal analysis (hi-frequency component)
signal amplitudes
neutron
“bang”
“big bang”
dE/dx
temperature (ºC)
N
droplet diameter (m)
only this region capableof providing nucleation dE/dx
xtra
SI rate :
max
min
v
v
220 dv
v
)v(fF~Rate
~ A2
p
thrmin Am2
E~vbut there’s also F2,
arXiv:astro-ph/0703543
10 1001E-8
1E-7
1E-6
1E-5
1E-4LHe (1.2)
CRESST-II/CaWO4
31 kgd
XENON/Xe
136 kgd
Al2O
3 (2)
C4F
10 (6)
C4F
10 (8)
C4F
10 (10)
C4F
10 (16)
C4F
10 (25)
C4F
10 (50)
C4F
10 (2)
Al2O
3 (8)
SI
N(p
b)
Mw (GeV/c2)
CDMS/Ge
121 kgd