measurement of 40 ar(n,p) reaction and neutron capture on 40 ar and 136 xe tunl and duke univ. megha...
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Measurement of 40Ar(n,p) reaction and neutron capture on 40Ar and 136Xe
TUNL and Duke Univ.
Megha Bhike and Werner Tornow Duke University and
Triangle Universities Nuclear Laboratory
AARM meeting, March 4 2013
Motivation for the 40Ar(n,p), 40Ar(n,) and 136Xe(n,) Reaction Cross Section Measurements
TUNL and Duke Univ.
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
Standard decay
0 decay
AARM meeting, March 4 2013
Motivation for the 40Ar(n,p), 40Ar(n,) and 136Xe(n,) Reaction Cross Section Measurements
TUNL and Duke Univ.
Argon is a favorite detection and shielding medium in:
Future Long Baseline Neutrino Experiment
dark-matter search-DEAP
0 decay search-GERDA
AARM meeting, March 4 2013
Motivation for the 40Ar(n,p), 40Ar(n,) and 136Xe(n,) Reaction Cross Section Measurements
TUNL and Duke Univ.
Enriched Xenon Observatory (0 )
136Xe
KamLAND-Zen(0 )
AARM meeting, March 4 2013
Motivation for the 40Ar(n,p), 40Ar(n,) and 136Xe(n,) Reaction Cross Section Measurements
TUNL and Duke Univ.
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 137CsEnergy resolution of KamLAND = 4.2 %2422.7keV, 2463.3 keV, 2474.8 keV and 2490.4 keV
AARM meeting, March 4 2013
Status of the (n,) Measurements on 40Ar
TUNL and Duke Univ.
(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
Status of the (n,) Measurements on 136Xe
TUNL and Duke Univ.
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
Activation Measurements at TUNL
TUNL and Duke Univ.
DENIS
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
Neutron production
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)
Activation parameters Neutron TOF area
AARM meeting, March 4 2013
Activation Measurements at TUNL
TUNL and Duke Univ.
DENIS
Experimental SetupHigh Res. Gamma Spec.
C. Bhatia et al., PRC 86, 041602(R) 2012
4x60% HPGe detectors
Genie 2006 spec. system
Identical counting conditions
AARM meeting, March 4 2013
TUNL and Duke Univ.
41Ar g-Ray Signature
Measured 7000-8000 -g 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 g-Ray Signature
137Xe
137Cs 7/2+; 30.07 years
5/2+; 455.5, T1/2 < 0.1 ns
99.6(11)%
455.5 keV
31.2(5)%
Measured 300-550 -g 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
Experimental Results: 40Ar(n,)41Ar
TUNL and Duke Univ.
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
Experimental Results: 40Ar(n,p) 40Cl
TUNL and Duke Univ.
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
Experimental Results: 136Xe(n,)137Xe
TUNL and Duke Univ.
Cross sections are of mb level
TUNL data do not agree with both ENDF/B-VII.1 and TALYS-2012 evaluations
AARM meeting, March 4 2013
Future plans: 76Ge(n,)77Ge
TUNL and Duke Univ.
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
Summary
TUNL and Duke Univ.
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