MACHe 3 Prototype of a bolometric detector based

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MACHe 3: Prototype of a bolometric detector based on superfluid 3 He for the

MACHe 3: Prototype of a bolometric detector based on superfluid 3 He 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 MACHe 3: (CRTBT / LPSC) MAtrix of Cells of superfluid Helium-3

Missing Mass and non-baryonic Dark Matter • Flat Universe ≈ c=5. 1 Ge. V/m

Missing Mass and non-baryonic Dark Matter • Flat Universe ≈ c=5. 1 Ge. V/m 3 Wr + Wm + WL ≈ 1. 0 • Energy density of matter in the Universe M ≈ 1. 6 Ge. V/m 3 Wm ≈ 0. 3 WL ≈ 0. 7 Knop et al. (2003) Spergel et al. (2003) Allen et al. (2002)

Open questions in cosmology: baryons ≈ 0. 2 - 0. 3 Ge. V/m 3

Open questions in cosmology: baryons ≈ 0. 2 - 0. 3 Ge. V/m 3 Anomalies of galactic rotation curves Vitesse develocity rotation (km/s) Rotation km/s Presence of large scale structures imposes Measured Visible Matter contribution Standard Cold Dark Matter R 0=8. 5 kpc. VIRGO Honma et Sofue (1996) Simulation

Non-baryonic Dark Matter: Weakly Interacting Massive Particles Supersymmetric extension of Standard Model provides a

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 Ge. V/c 2) Missing Mass neutral in charge and color Weak interaction cross section with ordinary matter Direct detection Scalar interaction Axial interaction Edelweiss, CDMS, CRESST, Zeplin DAMA/Libra, Picasso, Simple, MACHe 3 Ge, Si, Ca. WO 4, Xe Na. I, F , 3 He

Project of bolometric detection based on 3 He • Spin 1/2 nucleus axial interaction

Project of bolometric detection based on 3 He • Spin 1/2 nucleus axial interaction with neutralino • High transparency to g-rays • Nuclear neutron capture reaction • Limited recoil energy range: Erecoil < 6 ke. V At ultra-low temperature (100 m. K, superfluid) • Specific heat exp(-D/k. BT) • Absolute purity • Liquid but: expensive, technologically challenging, …

MACHe 3 Project: Potential of a bolometric detector involving 10 kg / 1000 cells

MACHe 3 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 2004 S M CD inary prelim

Vibrating wire thermometry at ultra-low temperatures

Vibrating wire thermometry at ultra-low temperatures

The Vibrating Wire Resonator H Induced voltage V 3 mm Nb. Ti Monofilament (4.

The Vibrating Wire Resonator H Induced voltage V 3 mm Nb. Ti Monofilament (4. 5 mm) (Photo E. Collin) V (m. V) I 0 eiwt

Ballistic quasiparticle gas Non-linear damping E 2 3 4 +p. Fv -p. F 0

Ballistic quasiparticle gas Non-linear damping E 2 3 4 +p. Fv -p. F 0 p. F D p Doppler shift of dispersion curves selective scattering of quasiparticles (Andreev scattering) (Fisher et al. , PRL 1989) vrms (mm/s) 1 Excitation force (p. N)

Bolometric detection and calibration 3 -cell bolometer 6 mm Stycast sealing A 15 mm

Bolometric detection and calibration 3 -cell bolometer 6 mm Stycast sealing A 15 mm H B C Orifice for thermalisation (200 mm ) Gold sheet with 57 Co Copper sheet (25 mm) VWRs (4. 5 et 13 mm) Copper support connected to silver sinters

Response to an instantaneous heat release Thermal equilibrium time A Instantaneous heat release Wret

Response to an instantaneous heat release Thermal equilibrium time A Instantaneous heat release Wret (Hz) Relaxation time of the bolometer Response time of thermometer time (s) Dynamical response of thermometer

Bolometric calibration coefficient Specific heat of quasiparticle gas Calibration coefficient Vibrating Wire damping +

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

Heat capacities W (Hz) 0. 01 0. 15 0. 4 1 5 Cqp CABS

Heat capacities W (Hz) 0. 01 0. 15 0. 4 1 5 Cqp CABS (Halperin) C (j/K) Cadd (Greywall) T (m. K)

Bolometric calibration by pulsed heating linear dependence H(Upuls ) Bradley et al. , PRL

Bolometric calibration by pulsed heating linear dependence H(Upuls ) Bradley et al. , PRL 1995; Bäuerle et al. , PRB 1998 Intrinsic losses in heater Amplitude (a. u. ) Energy injection by heater-VWR Lost energy fraction heater V I time (s) Wmes(Hz) thermometer H time (s)

Detection spectra: neutrons, muons and low energy electrons • Comparison to known energy sources

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

Ionization/scintillation Discrimination of electron recoils Electron recoil Nuclear recoil Heat

Ionization/scintillation Discrimination of electron recoils Electron recoil Nuclear recoil Heat

Neutrons Elastic diffusion nuclear neutron capture m 3 He≈ mn fast thermalisation of neutrons

Neutrons Elastic diffusion nuclear neutron capture m 3 He≈ mn fast thermalisation of neutrons fast neutron thermalisation and nuclear capture : good neutron background discrimination

Neutrons • good agreement with description of detector Detection spectrum at Wbase=0. 7 Hz

Neutrons • good agreement with description of detector Detection spectrum at Wbase=0. 7 Hz Moderated Am. Be source • Heat deposition : Coups ( Bäuerle et al. , Nature 1995) • Energy deficit of 15 % - Scintillation ? - Topological defects ? 3 H- 10 mm Meyer, Sloan, JLTP 1998 1 mm p 70 mm p=0 bar

Low energy electrons Radioactive decay Source is in situ (cell B) Moulin et al.

Low energy electrons Radioactive decay Source is in situ (cell B) Moulin et al. , to appear Electrons produced in gold sheet g-rays 21. 7 Internal conversion electrons 27. 9 57 Co emission Pile-up Auger electrons 0. 6 1 5. 5 7. 3 10 13. 6 14. 4 122 100 136 E (ke. V)

 • Detection of low energy electrons from 57 Co Expected energy range of

• Detection of low energy electrons from 57 Co Expected energy range of neutralino signal reached Wmes(m. Hz) • Detection threshold and resolution at ke. V level time (s)

Electron detection spectrum • resolution of low energy emission spectrum of 57 Co •

Electron detection spectrum • resolution of low energy emission spectrum of 57 Co • Comparison to 14 ke. V peak with bolometric calibration Energy deficit of f. UV(e-, 14 ke. V)≈26 5% UV Scintillation • Energy dependence of scintillated fraction? f. UV(e->100 ke. V)≈50% (Mc. Kinsey et al. , NIMA 2002) Analysis LPSC, d 5, B=100 m. T, W 0=430 m. Hz S/B>5 cell A (without source) cell B (with source)

Cosmic muons • Cosmic muon flux: coincidence • Large cross section (100 barns) linear

Cosmic muons • Cosmic muon flux: coincidence • Large cross section (100 barns) linear energy deposition (ionisation) d. E/dx=1. 9 r[g/cm 3]Me. V/cm Wmes(Hz) Surface 150 / m 2. s Underground (Gran Sasso) 2. 3 10 -4 / m 2. s Expected energy deposition in bolometers ~ 70 ke. V • Coincident detection across cells time (s)

 • Detection of cosmic muons: good agreement experience/simulation if f. UV(muons) ≈ 25

• Detection of cosmic muons: good agreement experience/simulation if f. UV(muons) ≈ 25 % Analysis and simulation LPSC (GEANT 4)

g-rays • s(g-3 He) < 1 -2 barn (diffusion Compton) << high-Z materials (photoelectric

g-rays • s(g-3 He) < 1 -2 barn (diffusion Compton) << high-Z materials (photoelectric effect) • Difficulty of a characterization by external g- source (Bradley et al. , PRL 1995) source: emission at 122 and 136 ke. V no Compton edge in detection specta • 57 Co Analysis LPSC cell A (without source) cell B (with source)

Outlook for Dark Matter search Detector project (Mayet et al. , NIMA 2002) •

Outlook for Dark Matter search Detector project (Mayet et al. , NIMA 2002) • 103 cells of 53 cm 3 • 10 kg 3 He target material • Underground laboratory 5 cm

Parallel detection of scintillation Moulin et al. , IVth. Int. Conf. Cosmo. Marseille 2004

Parallel detection of scintillation Moulin et al. , IVth. Int. Conf. Cosmo. Marseille 2004 GEANT 4 Simulation (LPSC): Intrinsic rejection of neutrons and g-rays Parallel g-ray discrimination necessary • Ultraviolet scintillation ? • Ionisation measurement ?

Alternative thermometry Microfabricated VWRs Si/Al (f ≤ 10 mm) Thermometry by NMR (Triquenaux et

Alternative thermometry Microfabricated VWRs Si/Al (f ≤ 10 mm) Thermometry by NMR (Triquenaux et al. , Physica B 2000) Homogeneous Precession Domain - NMR 100 m. K Incident particle 3 He 4 He, 30 mbar H S NMR signal Quantum coherent state of precession of magnetization

Conclusions • Experimental characterization of a prototype of a bolometric detector based on superfluid

Conclusions • Experimental characterization of a prototype of a bolometric detector based on superfluid 3 He - 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