Bulletin of the American Physical Society
2012 Fall Meeting of the APS Division of Nuclear Physics
Volume 57, Number 9
Wednesday–Saturday, October 24–27, 2012; Newport Beach, California
Session HC: Instrumentation III: TPC, Neutrons, beta-decay, Lasers |
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Chair: Betty Tsang, Michigan State University Room: Plaza III |
Friday, October 26, 2012 8:30AM - 8:42AM |
HC.00001: Simulation and tracking algorithm of an Active Target Time Projection Chamber (AT-TPC) Saul Beceiro, Wolfgang Mittig, Tan Ahn, Daniel Bazin, Remi Becquet, Zbigniew Chajecki, Adam Fritsch, Bill Lynch, Aimee Shore, Malek Tahar The AT-TPC is a new detector being made for studying low-energy reactions induced by secondary beams with high resolution and efficiency. In order to define the construction details, a robust tracking algorithm is needed. First, reaction tracks must be simulated realisticly, obtaining all kinematic observables. Our choice of micromegas as gas-amplifier implies a nonlinear response of the pad-signal with respect to position. A simulation was developed to perform the track reconstruction based on modeling the ionization track and the corresponding drift electrons through the AT-TPC. It takes into account the energy loss of ions in the gas target, the drift of the electrons, the detector's magnetic field, the electron amplification, and the response of the electronics. All the associated fluctuations are taken into account. To extract the physical variables Monte-Carlo simulation tracks are produced and then compared to track signals using a $\chi^2$ minimization to obtain the best parameters for the track. The program was used to test different pad patterns for the micromegas electron amplification detector in order to find the optimum pad layout for the construction of the detector. The code was also used to analyse tracks produced by alpha particles from a source in a test-device [Preview Abstract] |
Friday, October 26, 2012 8:42AM - 8:54AM |
HC.00002: Increasing gain and dynamic range for active-target time-projection chambers T. Ahn, W. Mittig, M. Tahar, R. Becquet, D. Bazin, S. Beceiro, Z. Chajecki, A. Fritsch, J.J. Kolata, W. Lynch, A. Shore Active-target time-projection chambers (TPCs) use the unique concept of using the tracking medium of the detector simultaneously as the target for studying nuclear reactions. This gives them the advantage of providing a thick target without losing resolution and a large acceptance for reaction products. However target gases for active-target TPCs such as H$_2$ and $^4$He have less favorable properties as compared to standard TPC gases, e.g. a lower maximum gain before sparking. Another difficulty is dealing with the broad range of possible recoil energies and particles resulting in a large span of energy losses. To overcome these difficulties, we tested two new methods using the MICROMEGAS electron amplification device. To handle the large energy loss dynamics, some MICROMEGAS' anode pads were polarized with a HV bias, resulting in different gains. This allows some pads to track high-energy loss particles such as high-Z ions while the others can track lower-energy loss particles such as energetic protons. For increasing the maximum gas gain, we doped the target gas with allene, which can increase the MICROMEGAS charge output by producing a larger number of ionized electrons through allene's conversion of UV radiation to free electrons. [Preview Abstract] |
Friday, October 26, 2012 8:54AM - 9:06AM |
HC.00003: Commissioning of the VANDLE neutron array with beta-delayed neutron spectroscopy William Peters, R. Grzywacz, M. Madurga, S. Paulauskas, D.T. Miller, M. Al-Shudifat, L. Cartegni, C.J. Gross, D.W. Bardayan, A.J. Mendez, K. Miernik, K. Rykaczewski, K.T. Schmitt, J.C. Batchelder, C. Matei, M. Wolinska-Cichocka, J. Blackmon, M. Matos, C. Rasco, J.A. Cizewski, M.E. Howard, B. Manning, A. Ratkiewicz, S. Ilyushkin, F. Sarazin The Versatile Array of Neutron Detectors at Low Energy (VANDLE) was commissioned to study the beta-delayed neutron emission spectra of over 30 fission-fragment nuclei for the first time. The nuclei were produced at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Lab and included many within possible $r$-process paths. A complete set of 48 detector modules, that are sensitive to 100 keV neutrons, were adjacent to 2 Ge clover gamma-ray detectors for coincidence measurements. Time of flight from a thin scintillator surrounding the implantation point to VANDLE determined the neutron energy. Details of the experiment and an assessment of the array's performance will be presented along with preliminary data from select nuclei. [Preview Abstract] |
Friday, October 26, 2012 9:06AM - 9:18AM |
HC.00004: Fast Neutron Spectroscopy with Cs$_2$LiYCl$_6$ Nathan D'Olympia, P. Chowdhury, C. Guess, T. Harrington, E. Jackson, S. Lakshmi, C.J. Lister, J. Glodo, R. Hawrami, K. Shah, U. Shirwadkar In the field of neutron detection, Cs$_2$LiYCl$_6$:Ce (CLYC) has recently attracted attention as a thermal neutron/$\gamma$-ray scintillator. Recent studies of fast neutron response of CLYC at the UMass Lowell 5.5 MV Van de Graaff accelerator has revealed the capability of directly measuring fast neutron energy spectra through the $^{35}$Cl(n,p) reaction. This detection mechanism, previously unreported in literature, yields discrete peaks with an average resolution of 9\%, making CLYC a promising candidate for fast neutron spectroscopy without resorting to time-of-flight techniques. MCNPX simulations corroborate our findings and explore the nature of the response function for energies up to 20 MeV. Plans for the unique capabilities of CLYC in the form of a versatile array will be presented. [Preview Abstract] |
Friday, October 26, 2012 9:18AM - 9:30AM |
HC.00005: ABSTRACT WITHDRAWN |
Friday, October 26, 2012 9:30AM - 9:42AM |
HC.00006: Beta-decay spectroscopy with a Planar Germanium Double sided Strip Detector Nicole Larson, Sean Liddick, Christopher Prokop, Scott Suchyta Traditional beta-decay spectroscopic studies at fragmentation facilities employ a double-sided silicon strip detector into which a cocktail beam of radioactive ions is implanted. The silicon detector monitors the arrival of each ion and detects the subsequent emission of a beta-decay electron. The beta-decay is correlated with a previously implanted ion in software based on position and temporal information. The thickness of the detector (typically 1 mm) combined with the low-Z of silicon make it difficult to efficiently detect all beta decays emitted from the radioactive isotopes. In an attempt to remedy this deficiency, a planar Ge double-sided strip detector (GeDSSD) has been incorporated into the Beta Counting System at National Superconducting Cyclotron Laboratory for decay spectroscopy studies. The higher Z and increased thickness of the GeDSSD compared to its silicon analogue should increase the detection efficiency for beta decays. Results from commission test will be presented. This work was supported in part by the National Science Foundation, Grant-PHY1102511 and the U.S. Department of Energy National Nuclear Security Administration under award number DE-NA0000979. [Preview Abstract] |
Friday, October 26, 2012 9:42AM - 9:54AM |
HC.00007: An advanced ion beam cooler and buncher for laser spectroscopy of rare isotopes at NSCL Bradley Barquest, Georg Bollen, Maxime Brodeur, Kortney Cooper, Jeffrey Kwarsick, Ryan Ringle, Stefan Schwarz, David Skutt, Chandana Sumithrarachchi An advanced beam cooler and buncher based on a gas-filled RF ion guide and trap is under development at MSU. The device will provide high-quality pulsed beams for collinear laser spectroscopy measurements of rare isotopes at the BECOLA facility at NSCL. A small transverse emittance allows for better overlap of the ion beam with laser light, and small longitudinal emittance bunches enhance the sensitivity of collinear laser spectroscopy measurements. Numerical simulations indicate the required cooler acceptance of 75 $\pi $ mm mrad @ 60 keV, and the extraction of ion bunches with longitudinal and transverse emittances of 2 eV-$\mu $s and 1 $\pi $ mm-mrad @ 60 keV are attainable. Design for the BECOLA cooler and buncher is complete, and construction is underway. A new electrode design and RF coupling scheme simplify mechanical design and operation. A number of the design features of the advanced beam cooler and buncher are being validated in a similar but separate RF ion guide device. Characterization of this ion guide and progress on the BECOLA cooler and buncher will be presented. [Preview Abstract] |
Friday, October 26, 2012 9:54AM - 10:06AM |
HC.00008: Photon Detection System for Collinear Laser Spectroscopy Experiments at NSCL A. Schneider, K. Minamisono, P.F. Mantica, A. Klose, B. Johnson The BEam COoler and LAser spectroscopy (BECOLA) facility [1] has been implemented for collinear laser spectroscopy experiments [2] with thermalized rare isotope beams at NSCL/MSU. A photon detection system [3], which consists of an ellipsoidal reflector and a photomultiplier tube, was developed to efficiently collect and detect laser-induced fluorescence in the near UV/blue and near IR/red wavelength regions. The photon detection system's sensitivity has been optimized so that the system may be applicable to rare isotopes with low production rates. The results of test measurements with offline ion/atom beams as well as comparisons with simulations using FRED optical engineering software [4] will be discussed.\\[4pt] [1] https://groups.nscl.msu.edu/becola\\[0pt] [2] S.L. Kaufman, Optics Communications, 17 309, (1976).\\[0pt] [3] S. Vinnikova, M.S. Thesis, Michigan State University, (2011).\\[0pt] [4] Photon Engineering; http://www.photonengr.com/software. [Preview Abstract] |
Friday, October 26, 2012 10:06AM - 10:18AM |
HC.00009: RX130 Robot Calibration Mario Fugal In order to create precision magnets for an experiment at Oak Ridge National Laboratory, a new reverse engineering method has been proposed that uses the magnetic scalar potential to solve for the currents necessary to produce the desired field. To make the magnet it is proposed to use a copper coated G10 form, upon which a drill, mounted on a robotic arm, will carve wires. The accuracy required in the manufacturing of the wires exceeds nominal robot capabilities. However, due to the rigidity as well as the precision servo motor and harmonic gear drivers, there are robots capable of meeting this requirement with proper calibration. Improving the accuracy of an RX130 to be within 35 microns (the accuracy necessary of the wires) is the goal of this project. Using feedback from a displacement sensor, or camera and inverse kinematics it is possible to achieve this accuracy. [Preview Abstract] |
Friday, October 26, 2012 10:18AM - 10:30AM |
HC.00010: Prototyping the magnetic environment for the measurement of the neutron EDM at SNS Ruediger Picker The SNS nEDM collaboration is developing a cryogenic EDM experiment with an ultimate precision goal of $<4 \cdot 10^{-28}$ e-cm; a factor of 100 better than the present lower limit. A finite measurement of the electric dipole moment (EDM) of the neutron would be a significant non-standard model discovery and a step towards explaining the matter-antimatter symmetry of the universe. A key prerequisite is a magnetic environment in the measurement cell that is very homogeneous and stable over the measurement time. At Caltech, we have built a half-scale prototype of the superconducting shield and magnets for characterization and optimization. The talk will introduce the setup and present recent results at cryogenic temperatures. [Preview Abstract] |
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