MACHe3: Prototype of a bolometric detector based on superfluid 3He for the search of nonbaryonic Dar

1
MACHe3 Prototype of a bolometric detector
based on superfluid 3He for the search of
non-baryonic Dark Matter

• C. Winkelmann
• J. Elbs
• E. Collin
• Yu. Bunkov
• H. Godfrin
• E. Moulin
• J. Macias-Perez
• D. Santos

MACHe3 (CRTBT / LPSC) MAtrix of Cells of
superfluid Helium-3
2
Plan de lexposé
I Masse manquante de lUnivers et Matière Sombre
non-baryonique II 3He superfluide et
thermométrie par Fil Vibrant aux ultra-basses
températures III Détection bolométrique et
calibration du détecteur IV Spectres de
détection neutrons, muons et électrons de basse
énergie V Perspectives pour la recherche de
Matière Sombre
3
Missing Mass and non-baryonic Dark Matter
Flat Universe ? ?c5.1 GeV/m3 Wr Wm WL
1.0 Energy density of matter in the Universe
?M 1.6 GeV/m3 Wm 0.3 WL
0.7
Knop et al. (2003) Spergel et al. (2003) Allen et
al. (2002)
4

• Open questions in cosmology
• Presence of large scale structures imposes
• rbaryons 0.2 - 0.3 GeV/m3
• ? Anomalies of galactic rotation curves

Rotation velocity km/s
Measured Visible Matter contribution
Standard Cold Dark Matter Simulation VIRGO
5
Non-baryonic Dark Matter Weakly Interacting
Massive Particles
Supersymmetric extension of Standard Model
provides a candidate neutralino c ? 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
6
Project of bolometric detection based on 3He
3He
Spin 1/2 nucleus ? axial interaction with
neutralino High transparency to g-rays
Nuclear neutron capture reaction Limited
recoil energy range Erecoil
At ultra-low temperature (100 mK, superfluid)
Specific heat ? exp(-D/kBT) Absolute
purity Liquid
but expensive, technologically challenging,
7
MACHe3 Project Potential of a bolometric
detector involving 10 kg / 1000 cells ?
reduction of neutron, muon and g-ray background
(Mayet et al., NIMA 2000). Preliminary analysis
by simulation (LPSC)
Mayet et al., PLB 2002
CDMS 2004 preliminary
8
Vibrating wire thermometry at ultra-low
temperatures
9
3He superfluide
fermion (2p n) 2e-
liquide jusquà T0 (p
A Tc 1 - 2.5 mK ? Transition superfluide
(onde-p) ? Phases multiples ? Phase B isotrope,
de type BCS D(k)D excitations
quasiparticules nqp?exp(-D/kBT) fraction
superfluide fraction normale vide
renormalisé gaz dilué de
quasiparticules
EF
D
T
10
The Vibrating Wire Resonator
I0 eiwt
H
V (mV)
Induced voltage V
3 mm
NbTi Monofilament (4.5 mm) (Photo E. Collin)
11
Hydrodynamics and slip
? Fermi liquid 3He liquide h?T-2
hydrodynamic analysis (Stokes Carless et al.,
JLTP 1983) ? At low temperatures corrections
for finite viscous mean free path lh ? Slip
effect (Højgaard Jensen et al., JLTP 1980) ? In
the superfluid Andreev scattering of
quasiparticles on surfaces ?  Quantum  slip
(Einzel et al., PRL 1984 Fisher et al., PRL 1989)
D(x)
Superfluid gap
Dbulk/3
wall
bulk
x
z
12
Towards a temperature standard viscosity and thermometry
Ta, 125 mm
h(T)/h(Tc) (21 bars) Ono et al., JLTP 1982
CW et al., JLTP (2004)
? Temperature calibration / platinum NMR ?
Extraction of an effective viscosity
heff(p,T) ? appliable to other VWRs
13
Gaz balistique de quasiparticules
Relation de dispersion BCS
E
1
2
3
4
kBT
Amortissement Fil Vibrant ? nqp
D
p
pF
-pF
0
vg
v
quasi-particule (vg.p0)
quasi-trou (vg.p
14
Ballistic quasiparticle gas
Non-linear damping
E
1
2
3
4
D
pFv
-pFv
vrms (mm/s)
p
0
pF
-pF
Doppler shift of dispersion curves? selective
scattering of quasiparticles (Andreev scattering)
(Fisher et al., PRL 1989)
Excitation force (pN)
15
Bolometric detection and calibration
3-cell bolometer
6 mm
Stycast sealing
Orifice for thermali-sation (200 mm )
A
15 mm
Gold sheet with 57Co
B
H
Copper sheet (25 mm)
VWRs (4.5 et 13 mm)
C
Copper support connected to silver sinters
16
Response to an instantaneous heat release
Thermal equilibrium time
Relaxation time of the bolometer
Wret (Hz)
Instantaneous heat release
Response time of the thermometer
time (s)
Dynamical response of the thermometer
17
Bolometric calibration coefficient
Specific heat of quasiparticle gas
Calibration coefficient
Vibrating Wire damping

Non-linear dependence of W on velocity ?
s(T,v)

We neglect - Adsorbed layers - Gap reduction
close to surfaces - Bosonic modes of
condensate ? non-exponential dependence of U on
T
18
Heat capacities
W (Hz)
1
0.4
0.15
5
0.01
Cqp
CABS (Halperin)
Cadd (Greywall)
C (j/K)
T (mK)
19
Bolometric calibration by pulsed heating
Energy injection by heater-VWR ? linear
dependence H(Upuls ) Bradley et al., PRL 1995
Bäuerle et al., PRB 1998
heater
Amplitude (a.u.)
V
Intrinsic losses in heater ? Lost energy fraction
I
time (s)
thermometer
H
Wmes(Hz)
time (s)
20
Bolometric calibration by pulsed heating
s?1/vT
21
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 (g-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
22
Discrimination of electron recoils
Electron recoil Nuclear recoil
Ionization/scintillation
Heat
23
Neutrons
Elastic diffusion m3He mn ? fast
thermalisation of neutrons
nuclear neutron capture
fast neutron thermalisation and nuclear capture
? good neutron background discrimination
24
Neutrons
good agreement with description of detector
Heat deposition (? Bäuerle et al., Nature
1995) Energy deficit of 15
Detection spectrum at Wbase0.7 Hz
Moderated AmBe source
Coups
- Scintillation ? - Topological defects ?
Meyer, Sloan, JLTP 1998
3H-
1 mm
p
70 mm
10 mm
p0 bar
25
Low energy electrons
Radioactive decay Source is in situ (cell B)

Moulin et al., to appear
g-rays
Electrons produced in gold sheet
Internal conversion electrons
21.7
27.9
Auger electrons
Pile-up
57Co emission
13.6
14.4
136
122
5.5
0.6
7.3
E (keV)
100
10
1
26
Detection of low energy electrons from 57Co
Detection threshold and resolution at keV level
? Expected energy range of neutralino signal
reached
Wmes(mHz)
time (s)
27
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)26?5
• UV Scintillation
• Energy dependence of scintillated fraction?
• fUV(e-100keV)50
• (McKinsey et al., NIMA 2002)

Analysis LPSC, d5, B100 mT, W0430 mHz
S/B5
cell A (without source)
cell B (with source)
28
Cosmic muons
Cosmic muon flux Surface 150 /
m2.s Underground (Gran Sasso) 2.3?10-4 / m2.s
Large cross section (100 barns) ? linear energy
deposition (ionisation) dE/dx1.9?rg/cm3MeV/cm
Expected energy deposition in bolometers 70
keV Coincident detection across cells
coincidence
Wmes(Hz)
time (s)
29
Detection of cosmic muons good agreement
experience/simulation if fUV(muons) 25
Analysis and simulation LPSC (GEANT4)
30
g-rays
s(g-3He) high-Z materials (photoelectric effect)
Difficulty of a characterization by external g-
source (Bradley et al., PRL 1995) 57Co
source emission at 122 and 136 keV ? no Compton
edge in detection specta
Analysis LPSC
cell A (without source)
cell B (with source)
31
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
32
Parallel detection of scintillation
Moulin et al., IVth. Int. Conf. Cosmo. Marseille
2004
GEANT4 Simulation (LPSC) Intrinsic rejection of
neutrons and g-rays ? Parallel g-ray
discrimination necessary Ultraviolet
scintillation ? Ionisation measurement ?
33
Alternative thermometry
Microfabricated VWRs Si/Al (f 10 mm) (Triquenaux
et al., Physica B 2000)
Thermometry by NMR
Homogeneous Precession Domain - NMR
Incident particle
100 mK
3He
H
S
NMR signal
4He, 30 mbar
Quantum coherent state of precession of
magnetization
34
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