C. Winkelmann J. Elbs E. Collin Yu. Bunkov H. Godfrin E. Moulin J. Macias-Perez D. Santos
description
Transcript of C. Winkelmann J. Elbs E. Collin Yu. Bunkov H. Godfrin E. Moulin J. Macias-Perez D. Santos
MACHe3: Prototype of a bolometric detector
based on superfluid 3He for the search of non-baryonic Dark Matter
C. WinkelmannJ. ElbsE. CollinYu. BunkovH. GodfrinE. MoulinJ. Macias-PerezD. Santos
MACHe3: (CRTBT / LPSC)MAtrix of Cells of superfluid
Helium-3
Missing Mass and non-baryonic Dark Matter
• Flat Universe ≈ c=5.1 GeV/m3
rm≈ 1.0
• Energy density of matter in the Universe
M ≈ 1.6 GeV/m3
m≈ 0.3 ≈ 0.7
Knop et al. (2003)Spergel et al. (2003)Allen et al. (2002)
Open questions in cosmology:
Presence of large scale structures imposes
baryons ≈ 0.2 - 0.3 GeV/m3
Anomalies of galactic rotation curves
Standard Cold Dark Matter Simulation VIRGO
Vit
esse
de
rota
tion
(km
/s)
R0=8.5 kpc Honma et Sofue (1996)
0
100
200
300
0 1 2 3
MesuréMatière Visible
R/R0
Rot
atio
n ve
loci
ty k
m/s
Measured Visible Matter contribution
Non-baryonic Dark Matter: Weakly Interacting Massive Particles
Supersymmetric extension of Standard Model provides a candidate:
neutralino stable (except annihilation) relic density massive (~ 100 GeV/c2) Missing Mass neutral in charge and color Weak interaction cross section with ordinary matter
Direct detection
~
Scalar interaction
Edelweiss, CDMS,CRESST, Zeplin
Ge, Si, CaWO4, Xe
Axial interaction
DAMA/Libra, Picasso, Simple, MACHe3
NaI, F , 3He
Project of bolometric detection based on 3He
• Spin 1/2 nucleus axial interaction with neutralino
• High transparency to -rays
• Nuclear neutron capture reaction
• Limited recoil energy range: Erecoil < 6 keV
At ultra-low temperature (100 K, superfluid)
• Specific heat exp(-/kBT)
• Absolute purity
• Liquid
3He
but: expensive, technologically challenging, …
CDMS 2004
preliminary
MACHe3 Project: Potential of a bolometric detector involving10 kg / 1000 cells reduction of neutron, muon and ray background(Mayet et al., NIMA 2000).Preliminary analysis by simulation (LPSC)
Mayet et al., PLB 2002
Vibrating wire thermometry at ultra-low temperatures
The Vibrating Wire Resonator
H I0 eit
Induced voltage V
3 mm
NbTi Monofilament (4.5 m)(Photo E. Collin)
F Id
l
H
boucleV
dS
B
dt
-0.05
0
0.05
478 480 482 484 486
V (V
)
fréquence (Hz)
W(T)
Signal en phase
Signal en quadrature
V (V
)
V () A
1 2 jf freso
W
Ballistic quasiparticle gas
+pFv
-pFv
pF-pF
E
p0
1 2 3 4
Doppler shift of dispersion curves selective scattering of quasiparticles (Andreev
scattering) (Fisher et al., PRL 1989)
v v0 kBT / pF
W(T ,v) EF
exp( / kBT )
1 exp( v / v0 )
v0 / v
Non-linear damping
vrm
s (m
m/s
)
Excitation force (pN)
Bolometric detection and calibration
A
B
C
H
Stycast sealing
Copper support connected to silver sinters
Gold sheet with 57Co
Copper sheet(25 m)
Orifice for thermali-sation (200 m )
15 mm
6 mm3-cell bolometer
VWRs(4.5 et 13 m)
Response to an instantaneous heat release
0.41
0.43
0.45
0.47
0 10 20 30
Wre
t (H
z)
temps (s)
y = 0.414+m1*(m3/(m3-0.77))*...
ErrorValue
9.0417e-050.054976m1
0.00429560.057101m2
0.0122635.1739m3
NA1.5681e-05Chisq
NA0.99978R
H
A
Response time of the thermometer
w 1/W
Dynamical response of the thermometer
Wret (t) Wbase A b
b w
exp( t / b ) exp( t / w ) (t)
Wre
t (H
z)
Thermal equilibrium timeeq 1 ms
Relaxation time of the bolometer
b 1/ Sorifice 5 s
Instantaneous heat release
W0 (t) Wbase A exp( t / b ) (t)
time (s)
Bolometric calibration coefficient
Specific heat of quasiparticle gas
Vibrating Wire damping
W exp / kBT
Calibration coefficient
dW
dU
A
U
1
T
Cqp C0
Tc
T
3 / 2
exp / kBT
We neglect - Adsorbed layers- Gap reduction close to surfaces - Bosonic modes of condensate
non-exponential dependence of U on T
Non-linear dependence of W on velocity
(T,v)
+
10-9
10-8
10-7
0.1 0.12 0.14 0.16
C (
j/K
)
T (mK)
Cqp
CABS (Halperin)
1 0.4 0.15 W (Hz)
Heat capacities
5 0.01
Cadd (Greywall)
Bolometric calibration by pulsed heating
1
1.02
1.04
1.06
1.08
0 5 10 15 20
temps (s)
0
2
4
6
0 1 2
temps (s)
Energy injection by heater-VWR
linear dependence H(Upuls )Bradley et al., PRL 1995; Bäuerle et al., PRB 1998
Upuls V.Idt
Intrinsic losses in heater
Lost energy fractionWheater Wheater
int Wheaterther
Am
plit
ude (
a.u
.)W
mes(
Hz)
H
I
V
heater
thermometer
time (s)
time (s)
Detection spectra: neutrons, muons and low energy electrons
• Comparison to known energy sources
• Characterization of the detector for different types of interaction
- ionizing interaction (electron recoil):predominant for light and charged particles(rays, electrons, muons)
- non-ionizing interaction (nuclear recoil):important for massive and neutral particles(WIMP, elastic neutron scattering)
• Ionization, secondary electrons excited atomic and molecular states
- heat- ultraviolet scintillation
Heat
Ion
izati
on
/sci
nti
llati
on
Discrimination of electron recoils
Electron recoilNuclear recoil
Neutrons
nuclear neutron capture
3He n 3H p 764 keV
Elastic diffusion
m3He≈ mn fast thermalisation of neutrons
capt(n /3He) 1000
E(eV)barns
diff (n /3He) 3 barns
fast neutron thermalisation and nuclear capture : good neutron background
discrimination
0
2
4
6
8
10
0.176 0.188 0.2 0.212
Cou
ps
H (Hz)
Detection spectrum at Wbase=0.7 Hz
Cou
ps
• good agreement with description of detector
• Heat deposition :
( Bäuerle et al., Nature 1995)
• Energy deficit of 15 %
Eneutrontherm 652 20 keV
- Scintillation ?
- Topological defects ?
p=0 bar
Neutrons
70 m10 m
1 m
p
3H- Meyer, Sloan, JLTP 1998
Moderated AmBe source
Low energy electrons
Radioactive decaySource is in situ (cell B) 27
57Co 2657Fe
10 1001 E (keV)
57C
o
em
issi
on
Pile
-up
Ele
ctro
ns
pro
duce
d in
gold
sheet
136122
Moulin et al., to appear
rays
Internal conversion electrons
Auger electrons
14.413.6
7.35.50.6
21.7 27.9
260
262
264
266
0 100 200 300
W(t
) (m
Hz)
temps (s)
10 keV
• Detection of low energy electrons from 57Co • Detection threshold and resolution at keV level Expected energy range of neutralino signal reached
Wm
es(
mH
z)
time (s)
cell A (without source)cell B (with source)
Electron detection spectrum
• resolution of low energy emission spectrum of 57Co
• Comparison to 14 keV peak with bolometric calibration Energy deficit of fUV(e-,14keV)≈265%
UV Scintillation
• Energy dependence of scintillated fraction?
fUV(e->100keV)≈50%(McKinsey et al., NIMA 2002)
S/B>5Analysis LPSC, d5, B=100 mT, W0=430 mHz
Cosmic muons
• Cosmic muon flux:
Surface 150 / m2.sUnderground(Gran Sasso) 2.310-4 / m2.s
• Large cross section (100 barns) linear energy deposition (ionisation) dE/dx=1.9[g/cm3]MeV/cm
Expected energy deposition in bolometers ~ 70 keV
• Coincident detection across cells
coincidence
Wm
es(
Hz)
time (s)
Analysis and simulation
LPSC (GEANT4)
• Detection of cosmic muons: good agreement experience/simulation if
fUV(muons) ≈ 25 %
rays
• (-3He) < 1-2 barn (diffusion Compton)
<< high-Z materials (photoelectric effect)
• Difficulty of a characterization by external source (Bradley et al., PRL 1995)
• 57Co source: emission at 122 and 136 keV
no Compton edge in detection specta
cell A (without source)
cell B (with source)
Analysis LPSC
Outlook for Dark Matter search
Detector project (Mayet et al., NIMA 2002)
• 103 cells of 53 cm3
• 10 kg 3He target material• Underground laboratory
5 cm
Parallel detection of scintillation
Moulin et al., IVth. Int. Conf. Cosmo. Marseille 2004
GEANT4 Simulation (LPSC):Intrinsic rejection of neutrons and rays
Parallel ray discrimination necessary
• Ultraviolet scintillation ?
• Ionisation measurement ?
Alternative thermometry
Microfabricated VWRsSi/Al (≤10 m)(Triquenaux et al., Physica B 2000)
Thermometry by NMR
H S
Quantum coherent state of precession of magnetization
Incident particle100 K
NMR signal
3He
Homogeneous Precession Domain - NMR
4He, 30 mbar
Conclusions
• Experimental characterization of a prototype of a bolometric detector based on superfluid 3He
- Vibrating Wire thermometry- Bolometry
• Detection spectra of neutrons, low energy electrons and muons
- neutralino detection threshold reached- good understanding of the detector
• Estimation of the scintillation yield of the irradiated superfluid
discrimination of electron recoils