1. MIcro-tpc Matrix of Cells of He3
MIMAC-He3
MIcro-tpc Matrix of Cells of He3
A new He3 detector for non-baryonic dark matter search
Daniel Santos & Emmanuel Moulin
Laboratoire de Physique Subatomique et de Cosmologie
Grenoble

2. (MIcroTPC MAtrix of Chambers
MIMAC-He3:
(MIcroTPC MAtrix of Chambers
Of Helium 3)
LPSC (Grenoble) : G. Bosson, V. Comparat, G.Duhamel, J. Genevey, R. Guglielmini, O. Guillaudin, T. Lamy, E. Moulin, J.A. Pinston, D. Santos, P. Sortais
Dapnia-Saclay: S. Aune, I. Giomataris
CPPM (Marseille): J. Bustó, C. Cerna
CdF (Paris): J. Dolbeau, Ph. Gorodetzky, T. Patzak, P. Salin
GPS (Paris) + LSBB (Rustrel): G. Waysand

3. of non-baryonic dark matter
3He for axial detection
of non-baryonic dark matter
spin 1/2 nucleus  axial interaction with
high signal/noise ratio : energy range ~ 2-5 keV
sensitive to M (WIMP) > 5 GeV
neutron capture signature: n + 3He  p + 1H keV
very low sensivity to -rays
no intrinsic X-rays

4. Recoil energy range for a 3He detector
Energy threshold
for 3He detector:
1keV
194.1 keV
117.8 keV
4.8 keV
 It must be convoluted by the QF(E) !

5. Background in the cell without source
57Co source in MACHe3 (LPSC+CRTBT)
E. Moulin, C. Winkelmann, J.Macias-Perez, Y. Bunkov, H. Godfrin,
D. Santos,( to be published)
Background in the
cell without source
5.5 keV
7.3 keV
13.6 keV
14.4 keV
21.7 keV
27.9 keV
12.8 keV

6. Expected electron spectrum
from 57Co source
(in a volume with mol)
conversion electrons :
7.3 keV (K shell)
13.6 keV (L shell)
14.4 keV (M shell)
auger electrons :
5.5 keV (K ~ 35.2%)
keV (L ~ 0.6%)
pile-up :
12.8 keV (ecK + eAK)
keV (ecL + eAL)
21.7 keV (gold eAL + ecK)
27.9 keV (gold eAL + ecL)
25 m thick gold foil
100 m thick
copper box
from 122 keV 
interaction in gold

7. (MIcroTPC MAtrix of Cells of He 3)
MIMAC-He3:
(MIcroTPC MAtrix of Cells of He 3)
spatial
High temporal resolution
energetic
recoil track projection
energy threshold < 1 keV
electron/recoil
discrimination

9. Distribution of energy depositions from 6.4 keV X-rays
Argon escape peak
(operating gas: Ar/isobutane 95/5)
X-ray detection threshold: 0.6 keV
CAST collaboration

10. Low energy spectrum from Micromegas in CASTFe
escape Cu Ar
escape Fe

11. Pixels (anode)
in CAST
Pitch: 350 μm

12. Range of recoils (He3) vs. Recoil Energy (SRIM-2003)

13. Diffusion & Charge collection D~ 200μm √ L[cm] => D~800 μm => 30 pixels ( L ~15 cm and pixels~250 μm )
He => 41 eV/ pair (e-ion) => 25 pairs/keV
With a gain G~3000 => e-/keV over
30 pixels
=> threshold ~ 2500e-
“gassiplex” does the job…but we’ll try to do better !

14. Drift velocity vs. Pressure

15. a/b ratio
simulation
(Geant 4)
a: major axis
b: minor axis
of the trajectory
projection
Isotropically
emitted
at 10 cm
of the anode
E. Moulin (LPSC)

16. Two-elastic interactions distance in He3 (2 atm) for a 8 keV neutron

17. Elastic-capture distance distribution in He3(2 atm) for a 8 keV neutron

18. Recoil Source : 3He2+ in the keV range

19. Source + filter : 3He2+ ( 6 to 50 KV)
Magnétron 300W

20. Recoil energy distribution after a polypropilene foil of 0
Recoil energy distribution after a polypropilene foil of 0.44μg/cm2 for acceleration energies of 45 and 50 keV

21. The lightest neutralino
lowest mass linear superposition of superpartners
of the gauge and higgs bosons:
~ ~ ~ ~ ~
= a1B + a2W3 + a3H1 + a4H2
neutral, colorless, only weak interaction
stable with R-parity conservation
non-relativistic at decoupling  CDM
relic density can be compatible with cosmological
observations

22. Light neutralinos ? (1) in universal models:
M1 , M2 gaugino mass unification at MGUT
 standard relation at EW scale (after RGE):
M1 = 5/3 tan2 W  0.5 M2
-   M1,M2 : m ~ M1
neutralino and chargino m± ~ M2
mass matrix:   M1,M2 : m ~ 
m± ~ 
LEP2 constraint on ± mass:
m± > 103 GeV  M2,  103 GeV  m  50 GeV

23. Light neutralinos ? (2) in non-universal models:
masses M1 , M2 non unified at MGUT
M1  M2/2 at EW scale
 LEP2 constraint not valid on neutralino mass
M1 = R M2 , R free parameter (constraint at EW scale relaxed)
constraint on the neutralino mass in non-universal models:
m  6 GeV A. Bottino et al, PRD69:037302, G. Belanger et al, JHEP0403:012,2004
… …

24. Axial cross section 3He- and rate in 10 kg 3He detector
M  6 GeV
  0.3
Exclusion curve for
0.01 day-1 background

25. Complementarity with scalar detection
CDMS 2004
Edelweiss 2003
Rate  0.01 day-1
Rate < 0.01 day-1

26. Summary
We have learned a lot with Mache3 (on simulations and interactions with muons, gammas, electrons and neutrons)
MIMAC-He3 prototype designed
He3 source for QF measurements designed and under construction
New electronic design in progress
First results of the prototype for the next IDM !!
Complementarities with the scalar experiments
(Ge, Xe,..)