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 -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

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 -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 levelTALYS – 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