Transcript Diapositive 1 - University of Sheffield

Enriched Xenon Observatory
for double beta decay
Z.Djurcic, D.Leonard, A.Piepke
Physics Dept, University of Alabama, Tuscaloosa AL
P.Vogel
Physics Dept Caltech, Pasadena CA
A. Bellerive, M. Dixit, C. Hargrove, D. Sinclair
Carleton University, Ottawa, Canada
W.Fairbank Jr., S.Jeng, K.Hall
Colorado State University, Fort Collins CO
M.Moe
Physics Dept UC Irvine, Irvine CA
D.Akimov, A.Burenkov, M.Danilov, A.Dolgolenko, A.Kovalenko, D.Kovalenko, G.Smirnov, V.Stekhanov
ITEP Moscow, Russia
J. Farine, D. Hallman, C. Virtue
Laurentian University, Canada
M.Hauger, L.Ounalli, D.Schenker, J-L.Vuilleumier, J-M.Vuilleumier, P.Weber
Physics Dept University of Neuchatel, Neuchatel Switzerland
M.Breidenbach, R.Conley, C.Hall, A.Odian, C.Prescott, P.Rowson, J.Sevilla, K.Skarpaas, K.Wamba,
SLAC, Menlo Park CA
E.Conti, R.DeVoe, G.Gratta, M.Green, T.Koffas, R.Leon, F.LePort, R.Neilson, S.Waldman, J.Wodin
Physics Dept Stanford University, Stanford CA
Double Beta Decay
1)  2 : ( A, Z )  ( A, Z  2)  e   e    ce   ce
d(n)
u(p)
d(n)
eec
ec
eu(p)
W
W
 
2 1
T1/ 2
G
2
 E0 , Z 
2)  0 : ( A, Z )  ( A, Z  2)  e   e 
d(n)
u(p)
W
m
W
d(n)
e-
ecR
eL
eu(p)
L  0
2 2
M GT
L  2
 
0 1
T1/2 
2
2
0 gV 0
G0 E0,Z  MGT
 2 M F m 2
gA
2N
m   m jU ejLU ejL
i 1
To improve on T120 and <m>:
need large source mass
lower background, better event signature
dN
dt
0+
2
c0
0
(A,Z+1)
(A,Z)
2+
e-e-
E0
0+
(A,Z+2)
Eee
E0
E0 (MeV)
Popular candidates
48Ca
48Ca
76Ge
76Ge
82Se
82Kr
100Mo
100Ru
128Te
128Xe
130Te
130Xe
136Xe
136Ba
150Nd
150Sm
232Th
232U
238U
238Pu
Abundance (%)
4.271
2.040
2.995
3.034
0.868
2.533
2.479
3.367
0.187
7.8
9.2
9.6
31.4
34.5
8.9
5.6
dir
dir
dir, geo
dir
dir, geo
dir, geo
dir
dir
0.858
1.145
100
99.3
melking
Isotopic enrichment for a gaseous substance like Xe is
most economically achieved by ultracentrifugation
Russia has enough
production capacity
to process 100 ton
Xe and extract
up to 10 ton 136Xe
in a finite time
This separation step that
rejects the light fraction
is also very effective in
removing 85Kr (T1/2=10.7 yr)
that is present in the
atmosphere from spent
fuel reprocessing
2
direct
geochem.
direct
T1calc
/2
T1ex/ 2p
T1calc
/2
T1ex/ 2p
T12/ 2 ( yr)
Nucleus
QRPA
Caltech
Shell model
StrasbourgMadrid
exp
48Ca
-
0.91
4.3 x 1019
76Ge
0.71
1.44
1.8 x 1021
82Se
1.5
0.46
8.0 x 1019
100Mo
0.6
-
1.0 x 1019
130Te
0.33
0.35
6.6 x 1020
128Te
0.27
0.25
2.0 X 1024
130Te
0.27
0.29
8.0 x 1020
136Xe
<1.0
<2.6
>8.1 x 1020
Enriched Xenon
Observatory
for double beta decay
Alabama, Caltech, Carleton, Colorado, UC Irvine, ITEP Moscow,
Laurentian, Neuchatel, SLAC, Stanford
136Xe:
136Ba++
e- e- final state can be tagged using
optical spectroscopy (M.Moe PRC44 (1991) 931)
Much improved signature!
2P
1/2
650nm
Ba+
493nm
system best studied (Neuhauser,
Hohenstatt, Toshek, Dehmelt 1980)
Very specific signature “shelving”
Single ions can be detected from a
photon rate of 107/s
4D
2S
1/2
metastable 47s
3/2
Two detector options under consideration
High Pressure gas TPC
• 5-10 atm, 50 m3 modules,
10 modules for 10 t
•Xe enclosed in a non-structural bag
•  range ~5-10cm:
can resolve 2 blobs
•2.5m e-drift at ~250kV
•Readout Xe scintillation with
WLSB (T0)
•Additive gas: quenching and
Ba++
Ba+ neutralization
•Steer lasers or drift Ba-ion to
detection region
Liquid Xe chamber
•Very small detector (3m3 for 10tons)
•Need good E resolution
•Position info but blobs not resolved
•Readout Xe scintillation
•Can extract Ba from hi-density Xe
•Spectroscopy at low pressure:
136Ba (7.8% nat’l) different
signature from natural Ba
(71.7% 138Ba)
•No quencher needed, neutralization
done outside the Xe
Energy resolution
s (E)/E  F(E/W) /E
F=0.19, W=22 eV
s(E)/E=0.13 % at 2.48 MeV !
Gotthard 5 bar xenon
e-, 232Th
a (from cathode), 210Po (238U chain)
s(E)/E=3.4 % at 1.59 MeV
quenching (a/e-)=1/6.5
s(E)/E= 2.7 % at 2.48 MeV
s(E)/E=1.1 % at 2.48 MeV !
ITEP-Moscow, Kharkov, Neuchâtel
Light detection (electroluminescence)
in xenon (+CF4?)
Grid (metallic cloth)
e- track
Multianode photomultiplier
UV photons
Anode (charge)
Two gap scheme:
Grid (metallic cloth)
Optical fibers x-y
Doped fibers :
1 step WLS UV (180 +/-20nm) to blue
or 2 step WLS with coated fibers
anode
Fibers (250 mm)
Major effort now: liquid xenon
Found a clear (anti)correlation between ionization and scintillation
1 kV/cm
~570 keV
Have demonstrated that we can get sufficient energy
resolution in LXe to separate the 2ν from the 0ν modes
We can do ionization
measurements
as well as anyone
Now we turn on our new
correlation technique…
3.3%@570keV
or 1.6%@2.5MeV
Fishing ions in LXe
230U
(20.8d)
α
226Th
5.99MeV
6.45MeV
222Ra
α
(38s)
6.68MeV
(35ms)
α
214Po
7.26MeV
(164ms)
α
210Pb
source α spectrum
as delivered by LLNL
and measured in vacuum
(30.5min)
α
218Rn
230U
7.83MeV
(22yr)
Initial Ra/Th ion
grabbing successful
As expected release from a
finite size metallic tip
is challenging
α spectrum from
whatever is grabbed
by the tip
(in Xe atmosphere)
Ion Trap R&D at UHV/atmospheric pressure
RF quadrupole trap
loaded in UHV from
a Ba dispenser
and e-beam ionizer
Xe can be injected
while observing
the ions
CCD Image of Ba+ ions in the trap
Trap
edge
Indeed we are talking about single ions: one can load the trap
with multiple ions and then observe the signal intensity as ions
are dropped one by one…
Zero ion background
All above in UHV;
Perform the same
experiment in noble
gas atmosphere
In parallel, build liquid TPC prototype, without Ba tagging
• Prototype Scale:
– 200 Kg enriched 136Xe
– All functionality of EXO except Ba identification
– Operate in WIPP for ~two years
• Prototype Goals:
– Test all technical aspects of EXO (except Ba id)
– Measure 2 mode
– Set decent limit for 0 mode (probe HeidelbergMoscow)
Massive materials qualification program
led by Alabama with contributions from
Carleton, Laurentian and Neuchatel
•Approximate detector simulation with material properties to
establish target activities
•NAA whenever possible (MIT reactor + Alabama)
•Direct Ge counting at Neuchatel, Alabama and soon Canada
•High sensitivity mass spectroscopy starting in Canada
•Alpha counting at Carleton and Stanford
•Rn outgassing measurements starter at Laurentian (Xe plumbing)
•Full detector simulation in progress
Detector
Teflon vessel
(356 on each side, 16 mm diameter 120 % QE in UV))
APD plane below crossed wire array
100 APD channels (7 APD grouped together) provide light and t0
200 ionization channels (groups of wires 100 x +100 y)
Can define fiducial volume
Cryostat Cross Section
Outer Door
Condenser
FC-87
Xenon
Chamber
Inner Door
Xenon Heater
should be
on this area
1” thick Thermal Insulation (MLIvacuum), not shown to scale
Xenon
Chamber
Support
FC-87
Inner Copper Vessel
Outer Copper Vessel
Full detector view
With Pb shielding
DoE’s Waste Isolation Pilot Plant (WIPP), Carlsbad NM
Status
• Enriched Xe in hand.
• Clean room installed at Stanford.
• WIPP agreement, including Environmental Impact,
complete.
• Cryostat being designed.
• Xe purification and refrigeration issues being
finalized
• Detector vessel, readout, and electronics being
engineered.
200 kg prototype, estimated sensitivity, without Ba tagging
Estimate background from radioactivity (2 negligible)
Mass
(kg)
Enrichment
(%)
Eff.
(%)
s/[email protected] MeV
(%)
Time
(yr)
Background
(events)
T1/20
(yr)
<m>(eV)
RQRPA
200
80
70
1.6
2
40
6.4*1025
0.28
V. A. Rodin et al. Phys.Rev. C68 (2003) 044302
Ultimate sensitivity, assuming
1) that the Xe chamber + Ba tagging gives 0 background from radioactivity...
2) that the energy resolution is s(E)/E=2 % (2 background!)
Mass
(kg)
Enrichment
(%)
Eff.
(%)
s/[email protected] MeV
(%)
Time
(yr)
Background
(events)
T1/20
(yr)
<m>(eV)
RQRPA
1000
10000
80
80
70
70
1.6
1.0
5
10
0.5 (use 1)
0.7 (use 1)
2.0*1027
4.1*1028
0.05
0.01
Conclusion:
With a coordinated effort, the meV region is within reach!