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 LH: Instrumentation I |
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Chair: Ernst Sichtermann, Lawrence Berkeley National Laboratory Room: Jewett Ballroom F |
Sunday, October 26, 2008 8:30AM - 8:42AM |
LH.00001: Status of the HELIOS Spectrometer at ATLAS Alan Wuosmaa The HELIOS device is a new spectrometer under construction at the ATLAS facility at Argonne National Laboratory designed to study transfer and inelastic scattering reactions in inverse kinematics, particularly with radioactive beams. The device consists of a large-bore, 3T superconducting solenoid with the magnetic axis aligned with the beam. Particles are transported along helical orbits from a target in the center of the solenoid to an array of position- sensitive silicon detectors placed along the solenoid axis. The construction of the spectrometer is well underway, including a new beam line, the components necessary to transform the magnet volume to a vacuum chamber, the detector arrays and moveable target mechanisms, all of which must function in a high magnetic field. The status of the construction and testing of the device will be presented. Work supported by the U. S. Department of Energy, Office of Nuclear Physics under grant numbers DE-FG02-04ER41320 and DE-AC02-06CH11357. [Preview Abstract] |
Sunday, October 26, 2008 8:42AM - 8:54AM |
LH.00002: Determination of neutron beam parameters of the DANCE flight path at LANSCE John Ullmann, Michal Mocko, Todd Bredeweg, Aaron Couture, Robert Haight, Marian Jandel, August Keksis, Guenter Muhrer, John O'Donnell, Olivier Roig, Robert Rundberg, David Vieira, Jan Wouters, Ching-Yen Wu, John Becker, Bayarbadrakh Baramsai, Andrii Chyzh Important characteristics of a moderated neutron beam include the time distributions of neutrons at a given energy (resolution function) and the absolute neutron flux. We will present a determination of the resolution function for the DANCE flight path at LANSCE. The determination is based on fitting resolved resonances from 1 eV to 1 keV using the SAMMY code. These results will be compared to Monte-Carlo calculations made using the MCNPX code with a detailed model of the target-moderator system and flight path. [Preview Abstract] |
Sunday, October 26, 2008 8:54AM - 9:06AM |
LH.00003: Calibration of a superconducting beta spectrometer using 66Ga Gregory Severin, Lynn Knutson, Elizabeth George, Paul Voytas, Sean Cotter We have constructed a new superconducting Wu spectrometer with roughly 1sr. acceptance and 2{\%} FWHM momentum resolution. The spectrometer measures the energy deposited into a 4MeV thick Si(Li) detector by betas that have been magnetically selected for their momentum. This simultaneous measurement of both momentum and energy deposition allows scattering effects to be accounted for, and provides an opportunity to compare data to Monte-Carlo simulations. These comparisons have been performed with both 207Bi and 66Ga, and the 66Ga results will be presented. [Preview Abstract] |
Sunday, October 26, 2008 9:06AM - 9:18AM |
LH.00004: Cyclotron gas stopper: simulations and predicted performance C.M. Campbell, S. Chouhan, C. Guenaut, D. Lawton, F. Marti, J. Ottarson, S. Schwarz, A.F. Zeller, P. Zavodszky, 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 $^{6}$Li to $^{150}$I. Details of the NSCL cyclotron-stopper and the simulation package developed to predict its performance will be presented. [Preview Abstract] |
Sunday, October 26, 2008 9:18AM - 9:30AM |
LH.00005: Compact High Resolution Isobar Separator for Decay Spectroscopy A. Piechaczek, V. Shchepunov, H.K. Carter, J.C. Batchelder, E.F. Zganjar, S.N. Liddick, H. Wollnik, B.O. Griffith A compact isobar spectrometer and separator, based on the Multi-Pass-Time-of-Flight (MTOF) principle, is being developed by the University Radioactive Ion Beam (UNIRIB) Consortium. Using N$_{2}$ as sample gas, a mass~resolving power of 113,000 (FWHM) and a transmission of $\sim $ 50 {\%} have been achieved after a time-of-flight of 9.7 ms. Coupled to the UNISOR mass separator at HRIBF, MTOF will provide isotopically pure samples of species around $^{100}$Sn, of neutron deficient rare-earth nuclei and of neutron-rich nuclei for use in decay studies and mass measurements. With beam cooling and bunching, we expect a mass resolving power (FWHM) of $\sim$ 400,000, transmission of $\sim $25 {\%} and isobaric suppression of adjacent elements $\sim $ 40,000. As a by product, MTOF will determine the masses of nuclei investigated with accuracies of 10$^{-6}$ , or about 100 keV for a mass A = 100 nucleus. Spectra demonstrating the separation of stable nuclides using a Bradbury-Nielsen gate will be shown. [Preview Abstract] |
Sunday, October 26, 2008 9:30AM - 9:42AM |
LH.00006: Radioactive Ion Beam Purification by Selective Adsorption C. Jost, H.K. Carter, B.O. Griffith, C.A. Reed, K.-L. Kratz, T. Stora, D.W. Stracener Isobaric contaminations in ISOL beams are a recurrent problem in nuclear physics experiments. Surface effects in the transfer line between target and ion source can be employed to achieve additional selectivity. Since interactions of the atoms' outer electrons with the surface determine adsorption behavior it can change drastically within an isobaric chain, introducing a chemical selectivity. Quartz transfer lines are currently applied at ISOLDE to reduce alkali contaminations [1]. We will conduct an on-line study of the adsorption behavior of fission products on a range of materials stable at high temperatures. Therefore a special target--ion source unit with a variable-temperature transfer line and interchangeable liner has been constructed in collaboration with the ISOLDE technical group. Results of first tests using new adsorption materials at the on-line separator test facility at Holifield Radioactive Ion Beam Facility, ORNL, will be presented. [1] Bouquerel et al., Europ. Phys. J. -- Spec. Top. 150, 277 (2006) [Preview Abstract] |
Sunday, October 26, 2008 9:42AM - 9:54AM |
LH.00007: Separation of H$_2$, HD and D$_2$ using Low Temperature Gas Chromatography C. Steven Whisnant, Travis Kelley, Ryan Burke, Patrick Hansen The frozen spin HD target developed for the study of photonuclear physics by the LEGS collaboration at Brookhaven National Laboratory (and now moved to JLab) requires high purity HD gas to produce targets with spin relaxation times on the order of months. Since this purity is not available commercially, the gas is distilled at low temperature to reduce the residual H$_2$ and D$_2$ contamination. Quantifying the remaining amount of these contaminants is important for preparing a target that obtains the desired polarization and spin relaxation time. To measure the relative concentrations of H$_2$ and D$_2$, a gas chromatography system has been developed that separates the isotopes of hydrogen. The system uses a 50 meter porous-layer open-tabular (PLOT) 5$\AA$ carbon molsieve column with an inner diameter of 0.53 mm held at temperatures near 150$K$. The carrier gas is neon. The signal is produced by measuring differences in thermal conductivity between hydrogen and neon. Under these conditions, not only are H$_2$ and D$_2$ separated from HD, but o-H$_2$ and p-H$_2$ are also well separated from one another. The resulting chromatograms are fit to extract areas and corrected for isotopic differences in thermal conductivity to produce relative concentrations. The analysis of several gas samples will be presented and the status of the method discussed. [Preview Abstract] |
Sunday, October 26, 2008 9:54AM - 10:06AM |
LH.00008: ABSTRACT WITHDRAWN |
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