Multi Purpose
Detectors/Targets
for
Low Energy Particle and
AstroPhysics (LEPAP):
Stefan Schönert
MPIK Heidelberg
Journées Neutrinos
Paris, 27/28. 11. 2003
Status & perspectives for LEPAP
’s as probe for astroand geophysics:
•Sun: precision meas.
pp, Be7, pep, CNO
 stellar evolution
•SN: dynamics of core
collapse, relic SN
•Earth: energetics of the
earth
Dark Matter:
-properties:
•direct detection of
•Sun:
non-baryonic DM
 full picture on osc.
 12
•Reactor:
 13(compl. to accelerator)
 msol² and 12
•DBD:
 Ł, Majorana type
 hierarchy, abs. mass scale
•Kinematics:
 absolute mass scale
Near future: several groups (in Europe) will define future
research projects  coherence & complementarity
Is there an experimental method
which can do everything ?
Isotopes/techniques for future exps.:
• He (SUN) (HERON)
• Ar (LB, p-decay, SUN,DM) (ICARUS,WARP)
• Ne (SUN, SN, DM) (CLEAN)
• Xe (DM, DBD, SUN) (XMASS, XENON, EXO,TPC)
• Ge (DBD, DM) (GeLN)
Eier legende
Wollmilchsau
• Mo (DBD, SUN, SN)
(MOON)
(oviparous wool-milk-pig)
• Nd (DBD)
• In (SUN) (LENS)
• Organic LS (SUN, REACTOR, EARTH, SN, p-decay)
(KamLAND, BOREXINO, LENA)
Specific requirements
(beyond low-background)
DBD:
•energy resolution
•single site vs.
extended evts.
•tracking
•daughter tagging
DM:
•low threshold
•annual modulation
Solar-:
•event-by-event discr. •Bq/m3 impurities
(recoil vs. ionization) •tag
•target mass > 10 t
SN dynamics:
•target mass 30kt
•tag
Requirements sometimes orthogonal!
“A Multi-Purpose Matrix” obviously non-diagonal
DM
DBD
Solar
SN
Geo
p-dec.
LBL
Xe
Ge
Mo
LS
Ar
x
x
x
-
x
x
?
-
x
x
x
-
x
x
x
x
-
?
x
x
x
x
•Matrix obviously incomplete
•No weight factor for competiveness
•Not included the most successful multi-purpose detector SK
Xe for DM
Xe+
Ionisation
+Xe
Electron/nuclear recoil
Xe2+
Excitation
+e(recombination)
Xe*
Electric Field
Xe
EL UV light
Xe** + Xe
+Xe
LXe
Xe2*
175nm
Triplet
27ns
175nm
Singlet
3ns
Smith, IDM2002
2Xe
eXe+
2Xe
Discrimination ionizing vs. recoil events by
•Pulse shape of scintillation light
•Electroluminescence / Scintillation
SC UV light
Xe for DM
Single phase detectors
“pragmatic approach”
• Zeplin 1:
• Discrimination recoil/ionization
via pulse shape
• XMASS
(100 kg)
Reduction of background,
self shielding
Xe for DM – XMASS 100kg
Low BG PMT
238U
1.8x10-2Bq
232Th 6.9x10-3Bq
40K
1.4x10-1Bq
60Co
5.5x10-3Bq
Xe for DM - XMASS
“pragmatic approach”:
•Single phase detector
•Minimizing external background by self shielding
•Minimizing internal background by purification
•Pulse shape discrimination?
800kg detector
80cm dia.
Xe for DM – XMASS 800 kg
external g ray (60cm, 346kg)
external g ray (40cm, 100kg )
/kg/day/keV
•
•
Dominant contribution is
from PMT
Assuming further 1/10
reduction of PMTs BG
22b, 8x1021 yr
7Be
pp
Dark matter (10-8 pb, 50GeV, 100 GeV)
Xe for DM – XMASS 800 kg
sensitivity
Spin independent
Seasonal variation
spectrum
Xe for DM
Two phase detectors:
“sophisticated approach”
Discrimination
recoil vs. ionization:
SC & EL
• Zeplin 1+i
• XMASS (2-Phase)
• XENON
Gas
anode
grid
Liquid
g-ray
cathode
Xe for DBD - XMASS
(c.f. dru=/kg/day/keV)
10 ton detector
External g ray BG only
Total vol.
10cm wall cut
20cm
30cm (FV 2.2t)
30cm + ½ PMT cut
Eff. @300keV~50%
XMASS 10t too small for DBD: self shielding at Qbb energies insufficient
Xe for DBD - XMASS
Symbolically…
Moriyama, NOON03
Xe for DBD - XMASS
Put ＰＭＴ away
Water shield
Xe vessel + wavelength shifter
Double focus
mirror
Water shield
Scintillation light
Xe vessel + wavelength shifter
PMTｓ
Xe for DBD – EXO
“very sophisticated approach”
EXO: Scintillation & Charge & Ba-tagging
Xe for Solar-
Detector with ~20t (10t fid. Vol)
2bb decay of 136Xe
t 1/2 theory=
8 x 1021 y
~1/100 reduction needed
sin22q = 0.77  0.03(stat.+SSM)
Ge for DBD
• Q(76Ge) = 2.039 MeV
• 5 detectors operating @ LNGS
• 10.96 kg active mass (86%
enriched)
• 125.5 mol of 76Ge
t1/20 > 1.9  1025 y
mee < 0.35 eV (90% c.l.)
Heidelber-Moscow Collaboration:
H.V. Klapdor-Kleingrothaus, A. Dietz, L. Baudis, G. Heusser, I.V.
Krivosheina, S. Kolb, B. Majorovits, H. Paes, H. Strecker, V.
Alexeev, A. Balysh, A.Bakalyarov, S.T. Belyaev, V.I. Lebedev,
and S. Zhukov
Eur. Phys. J. A 12 (2001) 147
76Ge:
sensitivity, exposure and
background
HEIDELBERG-MOSCOW Collaboration,
Eur. Phys. J. A 12 (2001) 147:
M·T = 35.5 kg y, b = 6 ·10-2
E ~ 4.2 keV
(kg y keV),
Sensitivity (with bgd):
mee  (b E / M T)1/4
Ge for DBD – “pragmatic approach”
Ge in liquid nitrogen/argon
Background in HD-M/IGEX dominated by
external impurities
 Strategy to improve sensitivity
(“pragmatic approach”):
reduction of background: 2 ·10-1 / kg y keV
(@2040 keV)  10-4 /kg y keV (operation
of “naked” Gediodes in liquid
nitrogen/argon
Increase of mass step by step  100 kg
New Initiative at
•MPIK Heidelberg: (H. Heusser, W. Hofmann, K.T. Knoepfle, S.
Schönert, B. Schwingenheuer, H. Simgen)
•Univ. Tuebingen
LOI to LNGS
•INR/ITEP
•Open for new partners : France ???
in spring
New concept under study “somewhat
sofisticated approach”: Ge in liquid Ar – new
ideas
• Replace
by
LN ( LN=0.8 g/cm³, 77 K)
LAr ( LN=1.4 g/cm³, 87 K)
 LAr/ LN (2.615 MeV) = 0.62
• Scintillation yield: 40,000 photons / MeV  Active
shielding medium!
(4 x organic liquid scintillator) Emission in XUV (~130 nm)
– Wavelength shifting required : Organic WLS and/or Xe addition
• Essential for cosmogenic activities: Co-60, Ge-68, …
• What’s about Ar-39, Ar-42 ?
LN2 shield against external
background radiation
LNGS: ~ 107 /m²/d
(2.6 MeV g)
~6 m
10-4 (kg keV y) -1
LN2
Space @ LNGS
~14 m
14.80 m
How small could a tank be?
• Lead layer submersed
in LAr
•
232Th
activity of lead
 tank Ø
• Preliminary results
30Bq/kg

Bgd. in LAr: example 42Ar
42Ar
/ natAr = 3·10-21 (30 Bq/kg)
[Barabash et al., LAr-TPC @ LNGS]
42Ar:
no vs. active suppression
b, g1,g2
Wavelength shifter
Reflector (VM2000)
No issue for DBD even without active suppression!
Active suppression of internal bgd:
example 60Co
Cosmogenic activities:
•Production after completion of crystal growth
•Exposure to cosmic rays above ground for 10 days: 0.18 Bq/kg [GENIUS]
60Co:
no vs. active suppression
b,g
Wavelength shifter Reflector (VM2000)
Reduction factor ~100
External bgd: example 2.615 MeV
gamma 232Th (208Tl) in lead shield
Flux from rocks(0.5 Bq / kg) and
concrete (5 Bq / kg) @ LNGS:
3.5 ·107 / (m² d)
New lead for shielding under study
with GEMPI @ LNGS:
<30 Bq / kg
[BOREXINO, Laubenstein]
232Th (208Tl):
no vs. active suppr.
g
Wavelength shifter Reflector (VM2000)
Lead
Simulation for 30 Bq/kg, inner-Ø: 2m, height: 2 m
Ge for DM
• Conventional diodes (“pragmatic approach”): no event-byevent discrimination
 reduction of background
 annual modulation signal (mass!)
• Cryo-detectors (“sophisticated approach”: Edelweiss,
CDMS): event-by-event discr.
Thermometer
(NTD Ge)
Ge Crystal
T~20mK
heat
ionization
Ge for DM – next generation
cryogenic detectors
Ge for DM - GeLN
Charge read-out only
Baudis et al. NIM A 426
(1999) 425
GENIUS (12 m diameter)
300 kg y, 1E-3/ kg y keV
Ge for DBD – potential of
cryodetectors
EDELWEISS:
identification of alphas by their anomalous quenching factor
Conclusion: Multi-Purpose
Detectors for DM/DBD/SOL ?
• Xe:
DM-det.  DBD-det.  Solar-det.
Solar-det  DM-det (isotope separation)
• Ge:
DBD-det  DM-det (convent./cryo.)
 Multi-Purpose Targets!
Appealing, since technological and experimental aspects
similar
Question of style ….
Bob Lanou LowNu2003:
To quote from a great philosophe Francaise:
“MIEUX VAUT FAIRE UNE
CHOSE BIEN
PLUTOT QUE D’EN FAIRE
PLUSIEUR MOINS BIEN.”
Advanced genetic engeneering:
Eier legende Wollmilchsau
(oviparous wool-milk-pig)
Catherine Deneuve in “Belle de Jour”