Measurement of 40 Ar(n,p) reaction and neutron capture on 40 Ar and 136 Xe TUNL and Duke Univ. Megha Bhike and Werner Tornow Duke University and Triangle Universities Nuclear Laboratory AARM meeting, March

Motivation for the 40 Ar(n,p), 40 Ar(n,  ) and 136 Xe(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

Motivation for the 40 Ar(n,p), 40 Ar(n,  ) and 136 Xe(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

Motivation for the 40 Ar(n,p), 40 Ar(n,  ) and 136 Xe(n,  ) Reaction Cross Section Measurements TUNL and Duke Univ.  Enriched Xenon Observatory ( 0  ) 136 Xe  KamLAND-Zen (0  ) AARM meeting, March

Motivation for the 40 Ar(n,p), 40 Ar(n,  ) and 136 Xe(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 40 Ar and 136 Xe upto En = 20 MeV  136 Xe(n,  ) 137 Xe,  decay, T 1/2 = 3.82 mins, Energy resolution of EXO = 1.67 % keV, keV,  -ray from 137 Cs Energy resolution of KamLAND = 4.2 % keV, keV, keV and keV AARM meeting, March

Status of the (n,  ) Measurements on 40 Ar TUNL and Duke Univ.  (n,  ) data for 40 Ar between 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 40 Ar(n,  ) 41 Ar cross section from 0.7 to 14.8MeV within 5-10 % AARM meeting, March

Status of the (n,  ) Measurements on 136 Xe 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 136 Xe(n,  ) 137 Xe cross section from 0.7 to 14.8 MeV within % AARM meeting, March

Activation Measurements at TUNL TUNL and Duke Univ. DENIS  T(p,n), D(d,n) and T(d,n) neutron sources  I p/d = 1 -2  A  E n = 0.7 – 14.8 MeV  Pulsed at 2.5 MHz Neutron production   n = (1-5)x10 7 n/(cm 2 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 (0 0 ) Activation parametersNeutron TOF area AARM meeting, March

Activation Measurements at TUNL TUNL and Duke Univ. DENIS Experimental Setup High Res. Gamma Spec. C. Bhatia et al., PRC 86, (R) 2012  4x  HPGe detectors  Genie 2006 spec. system  Identical counting conditions AARM meeting, March

TUNL and Duke Univ. 41 Ar  -Ray Signature  Measured  events after 2 hrs irradiation and 14 hrs counting time  Measured 10 energies in Nov 2012 – Feb 2013 runs AARM meeting, March

TUNL and Duke Univ. 137 Xe  -Ray Signature 137 Xe 137 Cs 7/2 + ; years 5/2 + ; 455.5, T 1/2 < 0.1 ns 99.6(11)% keV 31.2(5)%  Measured  events after 15 mins irradiation and 25 mins counting time  Measured 11 energies in Nov 2012 – Feb 2013 runs AARM meeting, March

TUNL and Duke Univ. Monitor Reactions Measurement of the neutron fluence using a set of witness foils mounted before & after the 136 Xe/ 40 Ar targets 197 Au(n,  ) T 1/2 = 2.69 d, E  = keV 115 In(n,n) T 1/2 = 4.49 h, E  =336.2 keV 197 Au(n,2n) T 1/2 = 6.17 d, E  = keV AARM meeting, March

TUNL and Duke Univ. Correction for parasitic neutrons AARM meeting, March

Experimental Results: 40 Ar(n,  ) 41 Ar 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

Experimental Results: 40 Ar(n,p) 40 Cl 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., C. Bhatia et al., PRC 86, (R) 2012 AARM meeting, March

Experimental Results: 136 Xe(n,  ) 137 Xe TUNL and Duke Univ.  Cross sections are of mb level  TUNL data do not agree with both ENDF/B-VII.1 and TALYS evaluations AARM meeting, March

Future plans: 76 Ge(n,  ) 77 Ge TUNL and Duke Univ.  no measurement from 0.7 to 14.8 MeV  Different evaluations   transition at keV  Ge target of 86% 76 Ge and 14% 74 Ge  test run at 2 MeV last week  taken from nndc AARM meeting, March

Summary TUNL and Duke Univ.  Complete cross section measurements of the 40 Ar(n,p) 40 Cl reaction  Capture cross sections on 40 Ar and 136 Xe 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