Bulletin of the American Physical Society
2011 Fall Meeting of the APS Division of Nuclear Physics
Volume 56, Number 12
Wednesday–Saturday, October 26–29, 2011; East Lansing, Michigan
Session CD: Instrumentation I |
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Chair: Grant O'Rielly, University of Massachusetts Dartmouth Room: Heritage |
Thursday, October 27, 2011 8:30AM - 8:42AM |
CD.00001: Ion Surfing: A new ion transport method for cryogenic gas catchers, simulations Amanda Gehring, Georg Bollen, Maxime Brodeur, Dave Morrissey, Gregory Pang Gas cells are the tool of choice to thermalize fast rare ion beams produced at projectile fragmentation facilities. After passing through solid degraders, the residual kinetic energy of the ions is dissipated through collisions with the gas atoms and ionization. Previously, ions were directed through a gas cell along a descending electrostatic potential gradient called a ``drag field.'' Some cells apply a drag field over electrodes with alternating (RF) fields to prevent the rare ions from colliding with the walls. ``Ion surfing'' is a new method proposed by Bollen [1] which replaces the drag field with a traveling wave superimposed with RF on numerous, thin electrodes. Large potential differences are no longer required for transport over long distances, and the traveling wave can transport ions at a greater speed. This method is being tested for the new cryogenic linear gas cell of the National Superconducting Cyclotron Laboratory at Michigan State University. We will present the concept and simulation results. \\[4pt] [1] G. Bollen, Int. J. Mass Spect. 299 (2011) 131 [Preview Abstract] |
Thursday, October 27, 2011 8:42AM - 8:54AM |
CD.00002: Ion surfing: a new mode for cryogenic gas catchers, experimental results Maxime Brodeur, Georg Bollen, Amanda Gehring, David Morrissey, Gregory Pang A new mode of ion-transport and collection for low-energy precision experiments at projectile fragmentation facilities was recently proposed by Bollen [1]. Present beam thermalization methods use gas-filled linear chambers equipped with sets of electrodes that provide an electrostatic gradient and/or alternating electric fields to transport the ions towards an extraction orifice. A new cryogenic linear gas cell of the National Superconducting Cyclotron Laboratory at Michigan State University will transport ions using only electrodynamic RF fields imposed on a series of linear conductive stripes. Traditionally, the ions migrate along a descending electrostatic potential gradient applied on the individual stripes, called the drag field, which requires a large potential difference to be applied in the gas for transport over long distances. The new method to transport the ions, called ``ion surfing,'' replaces the drag field with a traveling wave. The new method can transport ions at greater speed while simplifying the overall system. We will present the results of recent measurements for the transport of 85-Rb ions over distances up to 40 cm with various gas pressures at room temperature. \\[4pt] [1] G. Bollen, Int. J. Mass Spect.\textbf{ 299} (2011) 13 [Preview Abstract] |
Thursday, October 27, 2011 8:54AM - 9:06AM |
CD.00003: A miniature Penning trap for continuous magnetic field monitoring at the LEBIT Penning trap mass spectrometry facility Matthew Redshaw, David Lincoln, Ryan Ringle, Stefan Schwarz, Georg Bollen At the LEBIT Penning trap mass spectrometry facility, the mass to charge ratio of an ion is determined by measuring its cyclotron frequency in a strong magnetic field using a time-of-flight technique, which typically requires at least 50 ions for a single frequency measurement. The magnetic field strength is calibrated by interleaving frequency measurements on the rare isotope with measurements on a stable reference ion. However, this takes up valuable beam time and does not account for non-linear drifts in the magnetic field. These effects become more significant for rare isotopes with low production rates, where a single frequency measurement can take several hours or more. As an alternative scheme for monitoring variations in the magnetic field, we are developing an additional, miniature Penning trap (MiniTrap) to be used as a magnetometer. This MiniTrap can be operated independently from, and simultaneous to the rare isotope measurement. The cyclotron frequency of a small cloud of ions confined in the MiniTrap will be monitored via image charge detection using a Fourier transform technique. In this talk I will present the results of developmental and design studies for MiniTrap, and give an update on the status of the project. [Preview Abstract] |
Thursday, October 27, 2011 9:06AM - 9:18AM |
CD.00004: Development of tracking detector for transfer reactions with light beams at NSCL Sergey Ilyushkin, Frederic Sarazin, Dan Bardayan, Jeff Blackmon, Jolie Cizewski, Kate Jones, Steven Pain We report on the development of new beam tracking detectors to be used at NSCL. The new devices will address the current limitations on position resolution and open up the possibilities for transfer reaction experiments with light (Z$<$10) beams. The proposed design, likely based on a low pressure multiwire proportional chamber, and possible first experiments to take advantage of these detectors will be discussed. This work is supported by the Center of Excellence for Radioactive Ion Beam Studies for Stewardship Science. [Preview Abstract] |
Thursday, October 27, 2011 9:18AM - 9:30AM |
CD.00005: Development of the APOLLO Array Aaron Couture, Matthew Devlin, Hye Young Lee, John O'Donnell The role of neutron capture reactions is critical for nucleosynthesis processes far off of stability. Unfortunately, due to the radioactive nature the target isotopes of interest and the difficulty in producing a neutron target, these reactions will never be amenable to direct measurement. Further, for most astrophysical environments favored for the $r$~process, the required reaction networks are so large as to make direct experimental treatment of all of the reactions of interest beyond the range of what is feasible. Neutron transfer reactions, such as $(d,p)$, combined with intense beams of radioactive ions can help to elucidate the nuclear physics at play. The HELIOS instrument at Argonne National Laboratory has been successfully used to study a range of reactions in inverse kinematics. To complement this effort, we are designing a scintillator array to be used in conjunction with HELIOS to measure gamma-decay properties following neutron transfer. The design characteristics and optimization of the array, including plans for light collection and readout under the almost 3~T field will be discussed. [Preview Abstract] |
Thursday, October 27, 2011 9:30AM - 9:42AM |
CD.00006: Digital acquisition system for superheavy experiments David Miller, Robert Grzywacz, Krzysztof Miernik, Krzysztof Rykaczewski, Dieter Ackermann, Sophia Heinz, Sigurd Hofmann, Fritz He{\ss}berger The half-lives in the region of $Z \sim 120$ are expected to be in the range of several microseconds or shorter. Access to such short decays poses a challenge for traditional analog acquisition systems. A new digital acquisition system has been developed using Pixie digitizers to search for this fast radioactivity. The system was deployed at the decay station following the SHIP separator in parallel with its analog system to detect fast alpha decays following the implantation of fusion residues produced in the $^{248}\mathrm{Cm} +^{54}\mathrm{Cr}$ reaction. Its capabilities to detect sub-microsecond radioactivity and future possibilities will be presented. [Preview Abstract] |
Thursday, October 27, 2011 9:42AM - 9:54AM |
CD.00007: Status of CHICO2 C.Y. Wu, E. Kwan, A. Chyzh, D. Cline, A.B. Hayes, I.Y. Lee To fully exploit the potential of GRETINA, the development of auxiliary charged-particle detector arrays with matching position resolution is highly beneficial. CHICO2 is a part of this coordinated effort to improve the position resolution of CHICO for GRETINA by pixelation of the position sensing. Pixels are not readout individually instead interconnected in a checker-board pattern before being coupled to the delay line. The actual position is determined by the time difference between readouts from both ends of delay line. The proof-of-principle work on this technique has been demonstrated successfully in early 2010. Additional tests have been performed to measure the charge distribution for a given avalanche and the correlation between the pixel size and the time resolution, which helps to optimize the design of pixelation. A hybrid pixelation design was proposed to maximize the theta resolution and minimize the impact on the phi resolution. This design together with the results from those tests will be presented. This work is supported by DOE, LLNL Contract DE-AC52-07NA27344 and LBNL Contract DE-AC02-05CH11231 as well as the NSF. [Preview Abstract] |
Thursday, October 27, 2011 9:54AM - 10:06AM |
CD.00008: Characterization of a 1/2-scale prototype magnet at cryogenic temperatures for the SNS nEDM experiment Adrian Perez Galvan, Bradley Filippone The observation of a permanent electric dipole moment of the neutron at the current level of experimental sensitivity would indicate new physics beyond the Standard Model of particle interactions. In addition, it might also explain the mystery behind the matter-antimatter asymmetry of the Universe. Given these tantalizing implications, a new multi-institutional effort to measure the neutron electric dipole moment (nEDM) using ultra-cold neutrons and polarized $^{3}$He in a bath of superfluid $^{4}$He is currently underway at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. The search for the nEDM asks for stringent requirements on the uniformity of the magnetic environment at cryogenic temperatures. We present measurements of the uniformity of a half-scale version of the coil that will be used for the experiment. The measurements are performed while the coil is at a temperature of $\approx$~90 K. The results are in good agreement with previous room temperature measurements which suggest that magnetic non-uniformities due to thermal contraction are under control. [Preview Abstract] |
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