Transcript 40Ar(n, p) and neutron capture

Measurement of 40Ar(n,p) reaction
and neutron capture on 40Ar and 136Xe
Megha Bhike and Werner Tornow
Duke University and
Triangle Universities Nuclear Laboratory
AARM meeting, March 4 2013
TUNL and Duke Univ.
Motivation for the 40Ar(n,p), 40Ar(n,) and
136Xe(n,) Reaction Cross Section
Measurements
Standard  decay
0 decay
If detected, 0 decay would
indicate
• The neutrino is its own antiparticle
(Majorana Particle)
•Lepton number violation, contrary to
present formulation of standard model
•An absolute scale of neutrino mass (from
half-life) and nuclear matrix element
AARM meeting, March 4 2013
TUNL and Duke Univ.
Motivation for the 40Ar(n,p), 40Ar(n,) and
136Xe(n,) Reaction Cross Section
Measurements
Argon is a favorite detection and shielding
medium in:
 0 decay search-GERDA
 dark-matter search-DEAP
 Future Long Baseline Neutrino Experiment
AARM meeting, March 4 2013
TUNL and Duke Univ.
Motivation for the 40Ar(n,p), 40Ar(n,) and
136Xe(n,) Reaction Cross Section
Measurements
136Xe
 Enriched Xenon Observatory
(0 )
AARM meeting, March 4 2013
 KamLAND-Zen
(0 )
TUNL and Duke Univ.
Motivation for the 40Ar(n,p), 40Ar(n,) and
136Xe(n,) Reaction Cross Section
Measurements
Challenges in 0 Detection
 Long 0 decay half-life leads to low statistics in decay
spectrum
 Muon-induced spallation neutrons can produce background
signals indistinguishable from the signals of interest.
 Need to measure neutron induced cross sections on 40Ar and
136Xe upto En = 20 MeV
 136Xe(n, )137Xe,  decay, T1/2 = 3.82 mins,
Energy resolution of EXO = 1.67 %
2478.8 keV, 2463.3 keV,  -ray from 137Cs
Energy resolution of KamLAND = 4.2 %
2422.7keV, 2463.3 keV, 2474.8 keV and 2490.4 keV
AARM meeting, March 4 2013
TUNL and Duke Univ.
Status of the (n,) Measurements on 40Ar
 (n,) data for 40Ar between 0.1 -1
MeV
 Old measurements in low energy
region
Wright Air Devel. Centre Reports,
No.59, p.107 (1959) USA
 No data above 1 MeV
 Different evaluations
Goal: To measure 40Ar(n,)41Ar cross section from 0.7 to 14.8MeV
within 5-10 %
AARM meeting, March 4 2013
TUNL and Duke Univ.
Status of the (n,) Measurements on 136Xe
 few measurements in thermal
region
 No data in the entire energy range
from 0.7 to 14.8 MeV
 Different evaluation
Goal: To measure 136Xe(n,)137Xe cross section from 0.7 to 14.8 MeV
within 10-15 %
AARM meeting, March 4 2013
TUNL and Duke Univ.
Activation Measurements at TUNL
DENIS
Neutron production
 T(p,n), D(d,n) and T(d,n)
neutron sources
 Ip/d = 1 -2 mA
 En = 0.7 – 14.8 MeV
 Pulsed at 2.5 MHz
Activation parameters
Neutron TOF area
 n = (1-5)x107 n/(cm2 sec)
 High-purity Argon
(natural)/Xenon (enriched) gas
in high pressure stainless steel/
titanium sphere
 2 monitor foils (In & Au)
 n-flux monitoring: BC -501A
neutron monitor detector (00)
AARM meeting, March 4 2013
TUNL and Duke Univ.
Activation Measurements at TUNL
DENIS
Experimental Setup
High Res. Gamma Spec.
 4x60% HPGe detectors
 Genie 2006 spec. system
 Identical counting conditions
C. Bhatia et al.,
PRC 86, 041602(R) 2012
AARM meeting, March 4 2013
TUNL and Duke Univ.
41Ar
-Ray Signature
 Measured 7000-8000 -events after 2
hrs irradiation and 14 hrs counting time
 Measured 10 energies in Nov 2012 –
Feb 2013 runs
AARM meeting, March 4 2013
TUNL and Duke Univ.
137Xe
-Ray Signature
137Xe
99.6(11)%
5/2+; 455.5, T1/2 < 0.1 ns
31.2(5)%
137Cs
7/2+; 30.07
years
 Measured 300-550 -events after 15
mins irradiation and 25 mins counting time
 Measured 11 energies in Nov 2012 – Feb
2013 runs
AARM meeting, March 4 2013
TUNL and Duke Univ.
Monitor Reactions
Measurement of the neutron fluence using a set of witness foils mounted before &
after the 136Xe/40Ar targets
197Au(n,)
T1/2 = 2.69 d, E = 411.8 keV
115In(n,n)
T1/2 = 4.49 h, E =336.2 keV
197Au(n,2n)
T1/2 = 6.17 d, E = 355.7 keV
AARM meeting, March 4 2013
TUNL and Duke Univ.
Correction for parasitic neutrons
AARM meeting, March 4 2013
TUNL and Duke Univ.
Experimental Results: 40Ar(n,)41Ar
 Cross sections are of few mb
level
TALYS – 2012 agrees well with
TUNL data
 Good agreement with data
set of Bostrom et al.
AARM meeting, March 4 2013
TUNL and Duke Univ.
Experimental Results: 40Ar(n,p) 40Cl
 Fair agreement with the
ENDF-VII.1 evaluation up to
about 12.5 MeV and with
G4NDL3.13 above
 Good agreement with
measurement by Gray et al.,
1965.
C. Bhatia et al., PRC 86, 041602(R) 2012
AARM meeting, March 4 2013
TUNL and Duke Univ.
Experimental Results: 136Xe(n,)137Xe
 Cross sections are of mb level
 TUNL data do not agree with
both ENDF/B-VII.1 and TALYS2012 evaluations
AARM meeting, March 4 2013
TUNL and Duke Univ.
Future plans: 76Ge(n,)77Ge
 no measurement from 0.7 to
14.8 MeV
 Different evaluations
  transition at 2037.78 keV
 Ge target of 86% 76Ge and
14% 74Ge
 test run at 2 MeV last week
taken from nndc
AARM meeting, March 4 2013
TUNL and Duke Univ.
Summary
 Complete cross section measurements of the 40Ar(n,p)40Cl reaction
 Capture cross sections on 40Ar and 136Xe measured at 10 energies from
0.7 to 14.8 MeV. Plan to carry out measurements between 8 – 14 MeV
 These measurements are important for estimating potential background
events in the neutrinoless double-beta decay experiments, neutrino
detectors in general and dark matter experiments
AARM meeting, March 4 2013
TUNL and Duke Univ.