Multi Purpose Detectors/Targets
for Low Energy Particle and AstroPhysics (LEPAP):
Stefan SchönertMPIK Heidelberg
Journées NeutrinosParis, 27/28. 11. 2003
Status & perspectives for LEPAP
Dark Matter: •direct detection of non-baryonic DM
Near future: several groups (in Europe) will define future research projects coherence & complementarity
’s as probe for astro- and geophysics:•Sun: precision meas. pp, Be7, pep, CNO stellar evolution •SN: dynamics of core collapse, relic SN •Earth: energetics of the earth
-properties: •Sun: 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
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)• Mo (DBD, SUN, SN) (MOON)• Nd (DBD)• In (SUN) (LENS)• Organic LS (SUN, REACTOR, EARTH, SN, p-decay)
(KamLAND, BOREXINO, LENA)
Eier legende Wollmilchsau (oviparous wool-milk-pig)
Specific requirements (beyond low-background)
DBD: •energy resolution•single site vs. extended evts.•tracking•daughter tagging
DBD: •energy resolution•single site vs. extended evts.•tracking•daughter tagging
DM: •low threshold•annual modulation•event-by-event discr. (recoil vs. ionization)
DM: •low threshold•annual modulation•event-by-event discr. (recoil vs. ionization)
Solar-: Bq/m3 impurities•tag •target mass > 10 t
Solar-: Bq/m3 impurities•tag •target mass > 10 t
SN dynamics: •target mass 30kt•tag
SN dynamics: •target mass 30kt•tag
Requirements sometimes orthogonal!
“A Multi-Purpose Matrix” obviously non-diagonal
Xe Ge Mo LS Ar
DM x x - - ?
DBD x x x - -
Solar x ? x x x
SN - - x x x
Geo - - - x -
p-dec. - - - x xLBL - - - - x
•Matrix obviously incomplete •No weight factor for competiveness•Not included the most successful multi-purpose detector SK
Xe for DM
Discrimination ionizing vs. recoil events by •Pulse shape of scintillation light•Electroluminescence / Scintillation
Xe
LXe
Electric Field
e-
Xe+
SC UV light
EL UV lightXe*
+Xe
Xe2*
Triplet
27ns
Singlet
3ns
2Xe2Xe
175nm175nm
Xe** + Xe
Xe2+
+e-
(recomb-ination)
Xe+
+Xe
Ionisation
Excitation
Electron/nuclear recoil
Smith, IDM2002
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 1.8x10-2Bq232Th 6.9x10-3Bq40K 1.4x10-1Bq60Co 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/k
g/d
ay/k
eV
pp
7Be
, 8x1021 yr
• Dominant contribution is from PMT
• Assuming further 1/10 reduction of PMTs BG
external ray (60cm, 346kg)
external ray (40cm, 100kg )
Dark matter (10-8 pb, 50GeV, 100 GeV)
Xe for DM – XMASS 800 kg sensitivity
Spin independent
spectrumSeasonal variation
Xe for DM
Two phase detectors: “sophisticated approach”Discrimination recoil vs. ionization: SC & EL
• Zeplin 1+i • XMASS (2-Phase)• XENON
Dri
ft T
ime
E
anode
e-grid
cathode
~1μ
s~4
0 ns
Gas
Liquid
-ray
Xe for DBD - XMASS
XMASS 10t too small for DBD: self shielding at Q energies insufficient
Total vol.10cm wall cut20cm30cm (FV 2.2t)30cm + ½ PMT cutEff. @300keV~50%
10 ton detector External ray BG only
(c.f
. dr
u=/k
g/da
y/ke
V)
Xe for DBD - XMASSSymbolically…
Moriyama, NOON03
Xe for DBD - XMASS
Put PMT away
Water shield
PMT s
Water shield
Scintillation light
Double focus mirror
Xe vessel + wavelength shifter
Xe vessel + wavelength shifter
Xe for DBD – EXO“very sophisticated approach”
EXO: Scintillation & Charge & Ba-tagging
Xe for Solar-
1/2 theory=8 x 1021 y
~1/100 reduction needed
2 decay of 136Xe
Detector with ~20t (10t fid. Vol)
sin22= 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
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
/20 > 1.9 1025 y
mee < 0.35 eV (90% c.l.)
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 (kg y keV),E ~ 4.2 keV
Sensitivity (with bgd): mee (b E / M T)1/4
0.06 / (kg year keV)
0.01
0.001
0.0001
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•INR/ITEP•Open for new partners : France ???
LOI to LNGS in spring
New concept under study “somewhat
sofisticated approach”: Ge in liquid Ar – new ideas
• Replace LN (LN=0.8 g/cm³, 77 K)
by 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 )
LN2
~6 m
10-4 (kg keV y) -1
Space @ LNGS
14.80 m
~14 m
How small could a tank be?
• Lead layer submersed in LAr
• 232Th activity of lead tank Ø
• Preliminary results 30Bq/kg
Bgd. in LAr: example 42Ar42Ar / natAr = 3·10-21 (30 Bq/kg) [Barabash et al., LAr-TPC @ LNGS]
42Ar: no vs. active suppression
, 1,2
No issue for DBD even without active suppression!
Reflector (VM2000)Wavelength shifter
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
,
Reflector (VM2000)Wavelength shifter
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) [BOREXINO, Laubenstein]
New lead for shielding under study with GEMPI @ LNGS: <30 Bq / kg
232Th (208Tl): no vs. active suppr.
Lead
Simulation for 30 Bq/kg, inner-Ø: 2m, height: 2 m
Reflector (VM2000)Wavelength shifter
Ge for DM
• Conventional diodes (“pragmatic approach”): no event-by-event discrimination
reduction of background
annual modulation signal (mass!)• Cryo-detectors (“sophisticated approach”: Edelweiss,
CDMS): event-by-event discr.
heatheat
ionizationionization
ThermometerThermometer (NTD Ge)(NTD Ge)
Ge CrystalGe CrystalT~20mKT~20mK
Ge for DM – next generation cryogenic detectors
Ge for DM - GeLN
Baudis et al. NIM A 426 (1999) 425
GENIUS (12 m diameter)
Charge read-out only 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
“MIEUX VAUT FAIRE UNE CHOSE BIEN
PLUTOT QUE D’EN FAIRE PLUSIEUR MOINS BIEN.”
Bob Lanou LowNu2003:To quote from a great philosophe Francaise:
Catherine Deneuve in “Belle de Jour”
Question of style ….
Eier legende Wollmilchsau (oviparous wool-milk-pig)
Advanced genetic engeneering: