Bulletin of the American Physical Society
2008 Annual Meeting of the Division of Nuclear Physics
Volume 53, Number 12
Thursday–Sunday, October 23–26, 2008; Oakland, California
Session EG: Applications of Nuclear Physics |
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Chair: Eric Norman, Lawrence Berkeley National Laboratory Room: Jewett Ballroom C |
Friday, October 24, 2008 4:00PM - 4:12PM |
EG.00001: Energy-Dependent $Q$ Values for Fission Ramona Vogt We extend Madland's parameterization of the energy release in fission [1] to obtain the dependence of the fission $Q$ value for major and minor actinides on the incident neutron energies in the range $0\leq E_n \leq 20$ MeV.\\[2ex] [1] D. Madland, Nucl. Phys. A {\bf 772} (2006) 113. [Preview Abstract] |
Friday, October 24, 2008 4:12PM - 4:24PM |
EG.00002: Gamma Ray Multiplicity Comparison of a 2-Neutron and a 4-Neutron Emission $^{252}$Cf Spontaneous Fission D.L. Bleuel, L.A. Bernstein, J.T. Burke, M.D. Heffner, E.B. Norman, N.D. Scielzo, S.A. Sheets, N.J. Snyderman, M.A. Stoyer, M. Wiedeking, J. Gibelin, L.W. Phair, J. Mintz The correlation between $\gamma $-ray multiplicity and neutron multiplicity in the fission process is not currently well known. Competing theories predict opposite correlations and experiments have measured only average properties. We have measured the $\gamma $-ray multiplicity spectrum of $^{252}$Cf spontaneous fission using the LiBerACE array, comprised of six high-purity germanium (HPGe) Clover detectors, each surrounded by 16 bismuth-germanate (BGO) detectors. The Clovers were arranged in a cubic pattern around a 1 $\mu $Ci $^{252}$Cf source. Neutron multiplicity was determined for two cases by identifying known correlated fission products from prompt $\gamma $-rays observed in the HPGe detectors. No difference in the $\gamma $-ray multiplicity spectrum was observed for fissions that produced $^{106}$Mo/$^{144}$Ba (2 neutrons) compared to those producing $^{106}$Mo/$^{142}$Ba (4 neutrons). [Preview Abstract] |
Friday, October 24, 2008 4:24PM - 4:36PM |
EG.00003: Precision Cross Section Measurement for the $^{241}$Am($\gamma$,$n$) Reaction at HI$\gamma$S A. Tonchev, A. Hutcheson, C.R. Howell, E. Kwan, G. Rusev, W. Tornow, S. Hammond, H.J. Karwowski, C. Huibregtse, J.H. Kelley, D.L. Vieira, J.B. Wilhelmy, M.A. Stoyer The photodisintegration cross section on radioactive $^{241}$Am target has been measured for the first time using monoenergetic $\gamma$-ray beams from the HI$\gamma$S facility. Induced activity from $^{240}$Am produced via the ($\gamma$,$n$) reaction was measured by the activation technique using high resolution HPGe detectors. The ($\gamma$,$n$) cross section was determined both by measuring the absolute $\gamma$-flux and by comparison to the $^{197}$Au($\gamma$,$n$) cross section used as a standard. In the following, we report new data for the excitation function of the $^{241}$Am($\gamma$,$n$ ) reaction from near threshold to 16 MeV incident $\gamma$-ray energy and we compare the data with statistical nuclear-model calculations performed with the GNASH, EMPIRE, and TALYS codes. [Preview Abstract] |
Friday, October 24, 2008 4:36PM - 4:48PM |
EG.00004: Ultra-Low $^{40}$K Background Measurements for SNO+ using AMS Daniel Robertson, John Baker, Matthew Bowers, Philippe Collon, Jaret Heise, Kara Keeter, Christoper Schmitt, Eddie Tatar, Charles Taylor, Wenting Liu Whilst striving for better sensitivity, experiments studying rare process such as neutrino and dark matter interactions are forced underground to achieve the ultra-low levels of radioactive background they desire. In conjunction with this, Accelerator Mass Spectrometry (AMS) can be used to achieve the ultra-low sensitivity required for detector material selection. One project interested in such techniques is SNO+, which proposes to modify the existing SNO detector to study low-energy solar neutrinos as well as other neutrino properties via double-beta decay using a liquid scintillator called linear alkylbenzene (LAB). Due to the lower energy threshold of the detector, the present materials need to be re-evaluated for concentrations of $^{40}$K. Ultra-pure copper cathodes as well as samples of materials to be used in the detector have been prepared at Idaho State University and Idaho National Laboratory. These materials are being tested for levels of $^{40}$K at the Notre Dame AMS facility. Proof of principle and results from the first set of measurements will be discussed. This work is supported in part by NSF grant no. 0653642. [Preview Abstract] |
Friday, October 24, 2008 4:48PM - 5:00PM |
EG.00005: Measurement of $^{39}$Ar/Ar ratios using AMS on underground argon samples using the newly developed ultra-pure Al lined plasma chamber P. Collon, M. Bowers, F. Calaprice, C. Galbiati, C.L. Jiang, D. Henderson, W. Kutschera, H.H. Loosli, R. Pardo, M. Paul, E. Rehm, D. Robertson, C. Schmitt, R. Scott, R. Vondrasek, H.Y. Lee The first application of $^{39}$Ar AMS at the ATLAS linac of Argonne National Laboratory (ANL) to date ocean water samples relevant to oceanographic studies was most successful and has been reported on. In particular the use of a quartz liner in the plasma chamber of the Electron Cyclotron Resonance (ECR) ion source enabled a potassium reduction of a factor $\sim $100 compared to previous runs without liners and allowed measurements down to $^{39}$Ar/Ar = 4.2x10$^{-17}$. We are currently working on improving the AMS method for $^{39}$Ar by following two ion source development paths to allow for higher Ar beam currents coupled to lower $^{39}$K background rates. Both methods are combined with new cleaning techniques developed for removing both particulates and other materials from surfaces, largely driven by the semiconductor industry. The driving force for the use of AMS to measure $^{39}$Ar is to search for a source of argon that has a low concentration of $^{39}$Ar. Such a source of argon would be useful for new liquid argon detectors that are being developed for detecting dark matter WIMPs (Weakly Interacting Massive Particle), such as that to be installed at the new DUSEL (Deep Underground Science and engineering laboratory) facility at Homestake in the US. [Preview Abstract] |
Friday, October 24, 2008 5:00PM - 5:12PM |
EG.00006: Charge State Measurements with Photocell Detectors Chris Schmitt, Michael Carilli, Philippe Collon, Andreas Heinz, Jay LaVerne, Daniel Robertson, Sean Sullivan Measuring charge state distributions (CSD) of few electron systems, like lithium, through various targets can provide information to fill gaps in existing models. There is a need to look at target and ion velocity dependence for few electron systems and compare them with heavy ion interactions. Ultimately, there is a scientific need to probe the interactions between ion and target in order to understand the influences that each have on one another. The development, building, and characterizing of a photodiode array creates an effective tool for making measurements in ion beam experiments. Photodiodes as detectors provide distinct advantages over conventional silicon detectors in a laboratory setting. They are less sensitive to radiation damage, cost effective, easily replaceable, and a valuable teaching tool for undergraduates and graduate students alike. Other than a teaching tool their immediate experimental application will be as a beam monitor. The data presented shows test chamber results, the effects of beam induced damaged, and first CSD measurements. [Preview Abstract] |
Friday, October 24, 2008 5:12PM - 5:24PM |
EG.00007: Progress on a Polarimeter for the Deuteron EDM Search E.J. Stephenson The design of the storage ring for the deuteron electric dipole moment (EDM) search uses crossed {\bf E} and {\bf B} fields to nearly stop the magnetic moment precession of the deuteron in the ring bending magnets. This allows time for the EDM (whose predession is based on $E=\gamma{\bf v}\times{\bf B}$) to generate a detectable vertical polarization component [1]. A polarimeter for the EDM ring must monitor continuously and with high statistical precision. Recent tests at COSY-J\"ulich have demonstrated high efficiency ($\sim 1.5\%$) using a thick-walled carbon tube target that also determines the ring aperture. Extraction onto the target was tested using beam position ramping and beam heating with a cluster jet target or a white-noise electric field. Systematic errors were investigated. Continuous monitoring demonstration measurements were made using an RF solenoid whose frequency was ramped through the $1-G\gamma$ depolarizing resonance.\break [1] F.J. Farley {\it et al}, Phys.\ Rev.\ Lett.\ {\bf 93}. 052001 (2004). [Preview Abstract] |
Friday, October 24, 2008 5:24PM - 5:36PM |
EG.00008: Testing and Calibration of Novel Detectors for Nuclear and Plasma Physics Diagnostic Applications Zaheer Ali, Mike Haugh, Jim Tellinghuisen, Vladimir Glebov, Sam Roberts, Christian Stoeckl, Craig Sangster Calibrated chemical vapor deposition (CVD) diamond diodes, X-ray diodes (XRDs), and PIN diodes are used in nuclear and plasma physics diagnostic experiments, such as those conducted at the National Ignition Facility at Lawrence Livermore National Laboratory (LLNL). Calibrations of these diodes are conducted at the OMEGA Laser at the Lab for Laser Energetics of the University of Rochester, as well as at the Titan Laser in the Jupiter Laser Facility at LLNL. The OMEGA Laser is a 30-kilojoule one-nanosecond system designed for inertial confinement fusion and nuclear physics research. The Titan Laser is a picosecond system designed for plasma and X-ray studies. In addition, National Security Technologies, LLC, (NSTec) has built a new hard X-ray calibration facility (the ``HEX Laboratory''), where X-ray detector systems are also calibrated. In this paper we will present our methods of absolute and relative calibration, results of calibration, and the capabilities of the HEX Laboratory. [Preview Abstract] |
Friday, October 24, 2008 5:36PM - 5:48PM |
EG.00009: Nuclear Excitation via Auger Transitions (NEAT) Thomas Ward, Guy Emery, John Rasmussen, Hugon Karwowski, Carlos Castaneda Triggering (prompt de-excitation) of isomeric states produced in a process of coupling nuclear excitations to atomic shells via Auger transitions (NEAT) is studied. In this resonant process the nuclear transition energy between the two states must be less than the Auger transition energy. This requires the emitted Auger electron energy and the exact on-resonance nuclear excitation share the Auger transition energy. NEAT is compared to other proposed processes of nuclear excitation produced by x-rays (NEET), by electron capture (NEEC) and bound internal conversion (BIC), all of which suffer from off-resonance nuclear excitation except in those accidental cases where the energies may coincide. Estimates of the total resonance strength will be given for the case of $^{182m}Hf$ which has been extensively studied theoretically. A second case, $^{189}Os$, where NEAT processes may contribute to the nuclear resonance fluorescence (NRF) of the ground state to the 5.8hr isomeric state will also be examined as a good case for experimental verification of the NEAT process. [Preview Abstract] |
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