Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session G10: Nuclear Instrumentation |
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Sponsoring Units: DNP Chair: Michael Murray, University of Kansas Room: Governor's Square 10 |
Sunday, May 3, 2009 8:30AM - 8:42AM |
G10.00001: Cyclotron gas stopper: simulations and predicted performance C.M. Campbell, S. Chouhan, C. Guenaut , D. Lawton, F. Marti, J. Ottarson, S. Schwarz, P. Zavodszky, A.F. Zeller, G. Bollen, D.J. Morrissey, G. Pang Projectile fragmentation followed by in-flight separation provides fast, chemistry-independent access to a wide range of beta-unstable nuclides. To optimize their use, these exotic beams should be available at energies from rest to several MeV/u. This can be achieved by stopping fast beams in a volume of helium, extracting the stopped ions, and reaccelerating them to the desired energy. A ``cyclotron gas stopper'' has been proposed to overcome the limitations of current and proposed linear gas stoppers. The current design of the NSCL cyclotron-stopper uses a 2 meter diameter superconducting spiral-sector magnet with ion-guiding carpets in the central region. Complete simulations have been performed starting with realistic beam properties for 17 projectile fragments ranging from 6Li to 150I. Details of the NSCL cyclotron-stopper and the simulation package developed to predict its performance will be presented. [Preview Abstract] |
Sunday, May 3, 2009 8:42AM - 8:54AM |
G10.00002: Compact high resolution isobar separator for study of exotic decays V. Shchepunov, A. Piechaczek, H.K. Carter, J.C. Batchelder, E.F. Zganjar A compact isobar separator, based on the Multi-Pass-Time-of-Flight (MTOF) principle, is developed. A mass~resolving power (MRP) of 110,000 (FWHM) is achieved as spectrometer with a transmission of 50 - 80{\%}. The transverse beam acceptance and the energy acceptance are 42 $\pi $ mm mrad and about $\pm $ 2.5{\%}. Operated as a separator, molecules of N$_{2}$ and CO with $\Delta $M/M = 1/2500 or 10.433 MeV were separated with a Bradbury Nielsen gate. In that mode of operation, the MRP (FWHM) is about 40,000 after 120 laps. To inject radioactive ion beams into the separator, and to further improve its MRP, cooler and buncher RF quadrupoles were designed$^{1}$ and tested. A bunch width of 30 ns at 1{\%} of the peak height (FWHM = 9 ns) and a transmission in DC mode of 75 -- 80 {\%} were achieved. With such bunch parameters, MRPs of $\sim $ 400,000 (FWHM) are expected for the MTOF separator. At HRIBF, it will provide pure samples of exotic nuclides around $^{100}$Sn, of neutron deficient rare-earth nuclei and of neutron-rich nuclei. Incidental measurements of mass differences will determine Q$_{\beta}$ values with accuracies of $\sim $ 1{\%}. $^{1}$ V. Shchepunov and V. Kozlovskiy \textit{et al.,} to be published [Preview Abstract] |
Sunday, May 3, 2009 8:54AM - 9:06AM |
G10.00003: Commisioning of the windowless gas target at ORNL's Holifield Radioactive Ion Beam Facility B.H. Moazen, J.C. Blackmon, D.W. Bardayan, C.P. Domizioli, R. Fitzgerald, U. Greife, R.J. Livesay, M.S. Smith Direct measurements of many astrophysically relevant proton-induced reactions using radioactive ion beams require the use of hydrogen targets. The use of solid polypropylene targets is not always advantageous because of the large energy loss in the solid target and the existence of contaminant reactions on the carbon. At the Holifield Radioactive Ion Beam Facility, we have commissioned a windowless hydrogen gas target to be used in conjunction with the Daresbury Recoil Separator. The apparatus is connected to the beamline via 8 differential pumping stages (4 located upstream of the target and 4 downstream) and has a central chamber that can be filled with hydrogen gas at pressures up to ~8 Torr, while keeping good vacuum in the beamline. The setup and characterization of the target will be discussed along with its utilization in a number of measurements such as $^{17}$F(p,$\gamma$)$^{18}$Ne and $^{7}$Be(p,$\gamma$)$^{8}$B. [Preview Abstract] |
Sunday, May 3, 2009 9:06AM - 9:18AM |
G10.00004: Performance of the Neutron Imaging Camera (NIC) Seunghee Son, Stanley Hunter, Jason Link, Georiga de Nolfo, Noel Guardala The Neutron Imaging Camera (NIC) is based on the Three-Dimensional Track Imager (3-DTI) technology developed at NASA/GSFC for gamma-ray astrophysics applications. The 3-DTI, a large volume time projection chamber, provides accurate, $\sim $0.4mm resolution, 3-D tracking of charged particles. The incident direction of fast neutrons, E$_{n} \quad >$ 0.5 MeV, are reconstructed from the momenta and energies of the proton and triton fragments resulting from $^{3}$He(n,p)$^{3}$H interactions in the 3-DTI volume. We will discuss the NIC performance, including the angular and energy response, derived from a 2$\sim $3 MeV neutron accelerator beam. [Preview Abstract] |
Sunday, May 3, 2009 9:18AM - 9:30AM |
G10.00005: Development of the Real-Time Portable Neutron Spectroscope (NSPECT) for Detection and Identification of Special Nuclear Materials James Ryan, Christopher Bancroft, Peter Bloser, Ulisse Bravar, Colin Frost, Jason Legere, John Macri, Richard Woolf, Dominique Fourguette, Liane Larocque, Greg Ritter We describe the development of the Neutron Spectroscope (NSPECT) prototype detector capable of real-time neutron source location and identification. Real-time detection and identification fills an important gap in locating Special Nuclear Materials (SNM). NSPECT is suitable for locating SNM by detecting fission neutrons and reconstructing images of their source. NSPECT is an instrument with imaging and energy measurement capabilities that is sensitive to neutrons in the 1-20 MeV range. The detection principle is based upon multiple elastic neutron-proton scatterings in an organic scintillator. The instrument utilizes two detector panel layers. By measuring the recoil proton and scattered neutron energies, the direction and energy spectrum of the incident neutrons can be determined and discrete sources identified. Event reconstruction gives NSPECT the capability to provide an image of the source of interest. The design of NSPECT is a low power, low mass, rugged instrument, suitable for field deployment. Its modular design allows the user to combine multiple units for increased sensitivity. [Preview Abstract] |
Sunday, May 3, 2009 9:30AM - 9:42AM |
G10.00006: Commissioning of a Gamma Counting Facility in the Kimballton Mine Padraic Finnerty, Reyco Henning, Sean MacMullin, Kevin Macon, Alex Long, Richard Lindstrom, Henning Back, Steven Derek Roundtree The next generation of low background detectors will explore the frontiers of low energy neutrino physics, neutrinoless double beta decay, and direct dark matter searches. These experiments all require materials with minimal and tightly controlled radioactive contaminants. The KURF (Kimballton Underground Research Facility) is now home to a gamma counting facility, consisting of two HPGe (high purity germanium) detectors specifically designed for low background assay work. We discuss the technical and logistical considerations involved in the commissioning of a low background laboratory deep underground as well as our analysis techniques, including our sensitivity, efficiency, and activity calculations, which involve combining Monte Carlo and experimental data. Present status and sample analysis results will also be presented. [Preview Abstract] |
Sunday, May 3, 2009 9:42AM - 9:54AM |
G10.00007: Measured Nuclear Recoil Discrimination for HPGS, a Proposed Ton-Scale Dark Matte r Search in Room Temperature Gas C. Martin, D. Barton, M.P. Dion, J.H. Esterline, C.R. Howell, C.J. Martoff, P.F. Smith, W. Tornow The HPGS dark matter proposal is for a simple, room-temperature, ton-scale, 5-10 bar gas scintillation array with nuclear recoil discrimination by pulse-shape, aided by electric fields to suppress wall events. The first experimental confirmation of nuclear recoil discrimination by Xe gas scintillation pulse shape is reported here. Pulse shapes for $\gamma-$ and x-rays, neutrons, and $\alpha$ particles were measured using highly purified Xe gas at 1-6 bar with a UV-sensitive photomultiplier. Nuclear recoil and $\alpha$ pulses were dominated by recombination scintillation with time constant 250 ns, while gamma and x-ray scintillation was completely contained within 15 ns. We will present detailed comparison of our nuclear recoil pulse shape discrimination to liquid Xe, and discuss the outlook for simpler and lower cost room temperature ton-scale dark matter detectors. (We heartily thank A. Bolotnikov for access to high-purity Xe in his lab at Brookhaven National Laboratory.) [Preview Abstract] |
Sunday, May 3, 2009 9:54AM - 10:06AM |
G10.00008: The Polarized $^{3}$He Target performance at Jefferson Lab Chiranjib Dutta A polarized $^{3}$He target has been successfully used in a number of experiments at Jefferson Lab to study the neutron spin structure as well as the $^{3}$He structure. It has been upgraded for a set of experiments that began in October 2008. The recent improvements include a rapid spin-flip process and polarization in the vertical direction, allowing for polarization in any of the 3-D directions. Details of the target performance from the experiment E06-010 as well as the ongoing analyses will be presented. [Preview Abstract] |
Sunday, May 3, 2009 10:06AM - 10:18AM |
G10.00009: Performance of the BigBite Spectrometer during the Neutron Transversity Experiment in Hall-A Kalyan Allada The Hall-A E06-010 collaboration at Jefferson Lab recently measured the neutron target single spin asymmetry(SSA) in the semi-inclusive deep inelastic $^{3}He^{\uparrow}(e,e'\pi^{+/-})X$ reactions with a transversely polarized $^3$He target. A high-resolution spectrometer was used to detect pions in coincidence with the scattered electrons detected in the large acceptance BigBite spectrometer. The kinematical range, $x = 0.13\sim 0.41$, at $Q^2=1.31\sim3.10~(\mathrm{GeV}/c)^2$, focuses on the valence quark region. SSA data from this experiment will provide important information to extract the quark transversity distribution in semi-inclusive deep inelastic scattering. In this talk the performance of the BigBite spectrometer and trigger setup will be presented along with the progress on the data analysis. [Preview Abstract] |
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