NNSA Synergistic Activities at TUNL

1. COPPER 2H(d,n)3He Id =1mA beam pickoff 7.8 atm For the past several years, the TUNL REU program has started their 10-week summer session by measuring 28Si, 32S(n, n’ g) scattering using the NNSA HPGe array and TUNL’s NaI and liquid-scintillator detectors. This two-day exercise, which includes detector and electronics set-up, data taking and analysis, and oral presentation of observations introduces students to basic laboratory techniques and demonstrates the utility of high resolution spectroscopy for materials identification. REU Student Projects J.H. Kelley1, B. Fallin2, A. Hutcheson2, H.J. Karwowski3, E. Kwan2, A.P. Tonchev2, W. Tornow2 & Collaborators1Triangle Universities Nuclear Lab & North Carolina State University2Triangle Universities Nuclear Lab & Duke University1Triangle Universities Nuclear Lab & University of North Carolina at Chapel Hill The Triangle Universities Nuclear Lab is developing excellent facilities for studying (n, xn g) reactions. Resources provided through NNSA/DOE grant#DE-PS52-05NA25930have supplied four HPGE Clover Detectors, two Planar Detectors and supporting equipment. The research program at TUNL has developed components that utilize these resources to support both SSAA mission objectives and other curiosity driven nuclear-physics research objectives. NNSA Synergistic Activities at TUNL Neutron Beam Facility & g-ray Detectors HPGe and Planar g-ray detectors are supported on moveable plates that can cover lab angles ranging from 20O to 160O. A liquid scintillator neutron detector is positioned 2.0-meters from the target (at 0O) to monitor the neutron beam characteristics and flux. A second neutron beam area in the “NTOF Target Room” comprises a nominally unshielded neutron production cell that has been used in our 241Am(n, 2n) activation measurements. We plan to add a third neutron beam-line that is dedicated to this work. Two experimental halls at TUNL are dedicated to neutron beam research. In the Shielded Neutron Source Area (above) neutrons can be produced using either the 2H(d,n) or 3H(p,n) reaction. The ion beams are chopped and bunched prior to entering the FN Tandem accelerator. A copper collimator defines the neutron beam size and trajectory; further beam cleanup is provided by Pb and Li-doped plastic shielding. Activities In early 2006 we collaborated with Steve Yates et al., from the University of Kentucky to carry out a study of mixed symmetry states in 94Zr. In this experiment we utilized the high efficiency of our clover array, by measuring 94Zr(n,n’ g-g) two g-ray coincidence data. Preliminary results were presented at the DNP meeting in Nashville. Since 2003 a variety of measurements have been carried out utilizing the TUNL neutron beam-lines and the NNSA funded HPGe detector array. Our efforts are dominated by studies in the actinide region, though additional measurements have contributed interests in other projects, and student training exercises. Time Reaction Energies[MeV] May 2003 238U(n,2nγ)237U En = 6, 10 Aug 2004 238U(n,2n γ)237U En = 8, 10, 14 Feb 2005 90Zr(n,n'γ)90Zr En = 6 Feb 2005 89Yb(n,n'γ)89Yb En = 6 Feb 2005 112Sn(n,n'γ)112Sn En = 6.5, 7.5, 8.0 Feb 2005 124Sn(n,n'γ)124Sn En = 6.5, 7.5, 8.0 May 2005 235U(n,n'γ)235U En = 5 Jun 2005 235U(n,2n'γ)234U En = 12 Jun 2005 natHf(n,xn'γ) En = 12 Jun 2005 16O(n,n'γ)16O En = 7 Jun 2005 12C(n,n'γ)12C En = 7 Dec 2005 235U(n,2n'γ)234U En = 12.0 Jan 2006 235U(n,2n'γ)234U En = 10.0, 8.0 Jan 2006 181Ta(n,2n'γ)180Ta En = 14.5 Feb 2006 140Ce(n,2n'γ)139Ce En = 14.5 2006 94Zr(n,n’g-g)94Zr En = 5 2006 241Am(n,2n) Activation En 8-14 Jun 2006 natCu, natPb(n,n’g) En=8,12 Oct 2006 235,238U(n, 2ng) En=10 Dec 2006 241Am(n,2n) Activation En=8-16 Dec 2006 235U(n, 2ng)253U En=12 Jan 2007 235U(n,2ng)235U En=8 Insight into relevance of neutron induced reactions in deep underground experiments The Majorana Experiment • Open questions that can be addressed in 2b decay studies : • Are n Majorana particles? (self anti-particles) • Is lepton number conserved? (Standard Model) • 0nbb observation yields neutrino mass • could give insight into neutrino mass hierarchy Backgrounds from Pb(n,2n g) Cu(n,2n g) Preliminary Expected 0nbb Signal S2039 keV peak S 2039 keV Supported in part by the NNSA under the Stewardship Science Academic Alliances Program DOE grant #DE-PS52-05NA25930, and by DOE DE-FG02-97ER41033 (Duke) and DE-FG02-97ER41042 (NC-State).