Bulletin of the American Physical Society
2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008; St. Louis, Missouri
Session D14: Instrumentation for Low and Medium Energy Nuclear Physics |
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Sponsoring Units: DNP Chair: Peggy McMahan, Lawrence Berkeley National Laboratory Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), St. Louis G |
Saturday, April 12, 2008 1:30PM - 1:42PM |
D14.00001: A Dual-Axis Dual-Lateral Position Sensitive Silicon Detector for Charged Particle Detection Sarah Soisson, Brian Stein, L. May, R.Q. Dienhoffer, M. Jandel, G. Souliotis, D.V. Shetty, A.L. Keksis, S. Wuenschel, Z. Kohley, S.J. Yennello A dual-axis duo-lateral position sensitive silicon detector has been developed for charged particle detection. ~This type of detector has two conductive strips along opposite edges on each side of the detector. The contacts on the front are perpendicular to those on the back. When an incident particle hits the detector the charge is split between the contacts on each resistive layer. This allows for the total energy to be determined by the summation of either the contacts on the front side or the back side of the detector. The position of each axis can be easily determined using standard formulas such as X = (Q1-Q2)/(Q1+Q2), where Q is the charge collected from one contact. This design allows for position and energy to be determined without the necessity of software correction. Design of the detector, energy and position resolution will be presented. [Preview Abstract] |
Saturday, April 12, 2008 1:42PM - 1:54PM |
D14.00002: LBAS - A Non-Contact, High Precision Detector Alignment Tool M. Kilburn, A.M. Rogers, B. Nett, M.S. Wallace, W.G. Lynch, Z.Y. Sun Strip Si detectors provide high precision energy and position information for charged particles. Such information is needed for inverse kinematics experiments or for the reconstruction of particle unbound states of nuclei. In order to fully utilize this precision, it is often necessary to accurately align the strips to the exact beam spot on target and to the direction of the beam. We have developed a Laser Based Alignment System (LBAS) that permits high (sub millimeter) precision measurements of the location of a silicon strip detector without any mechanical contact between detector and measuring device. In this talk, the design will be described and its performance as an alignment tool for several recent strip detector experiments will be discussed. [Preview Abstract] |
Saturday, April 12, 2008 1:54PM - 2:06PM |
D14.00003: MASE (Multiplexed Analog Shaper Electronics): A novel approach to readout of a highly segmented silicon detector array S. Hudan, C.J. Metelko, M. Hodek, R.T. de Souza, A. Alexander, J. Poehlman A new approach in the signal processing and readout of highly segmented silicon detector arrays is described. The realization of this approach is Multiplexed Analog Shaper Electronics (MASE), an electronic system that allows the effective readout of highly segmented detector arrays when the occupancy in a single event is low. MASE combines the features of good energy resolution with time resolution adequate for random rejection. The MASE system is modular allowing for readout of a sixteen element silicon detector via a single board or a crate configuration of up to 4096 channels. Both the overall design and the performance characteristics of MASE are described. [Preview Abstract] |
Saturday, April 12, 2008 2:06PM - 2:18PM |
D14.00004: Evaluation of Large Area Planar Germanium Double-Sided Strip Detectors S. Gros, C.J. (Kim) Lister Large area segmented planar germanium detectors have many potential uses in basic research as well as in space science, medical imaging and homeland security applications. However, the intrinsic cost and technical complexity of their electronics have hindered progress in developing these position-sensitive gamma ray detectors. In this report we will compare large counters made with the traditional ``LEPS'' configuration, $i.e$. with lithium and boron contacts, with more recent detectors using amorphous germanium. We will present a basic series of tests which allow the performance of the counters to be evaluated and compared. Traditional MCA resolution and timing tests are necessary, but far from sufficient, conditions for identifying a superior detector. Charge loss, charge sharing, and cross talk all play significant roles in detector performance. These issues become critical when exploiting the detectors capability for reconstructing ``multi-hit'' events in gamma ray tracking or polarization experiments. This research was supported by the DOE Office of Nuclear Physics under contract DE-AC02-06CH11357. [Preview Abstract] |
Saturday, April 12, 2008 2:18PM - 2:30PM |
D14.00005: Determination of the Spectral and Intensity Distribution of the Mono-Energetic Gamma-Ray Beam at HI$\gamma$S Using a Large Volume HPGe Detector Gencho Rusev, Anton Tonchev, Anthony Hutcheson, Elaine Kwan, Werner Tornow, Chris Angell, Hugon Karwowski, John Kelley, Chanchang Sun, Ying Wu The High-Intensity Gamma-ray Source facility (HI$\gamma$S) provides $\gamma$-ray beams with small energy spread ($1-3$ \%) suitable for investigating the response of nuclides to dipole radiation. Nuclear resonance fluorescence experiments require precise knowledge of the intensity and the spectral distribution of the incident $\gamma$-ray beam in order to deduce the scattering cross section. We present a method for determining the energy spectrum of the $\gamma$-ray beam using a large volume HPGe detector. We monitor the $\gamma$-ray flux during in-beam experiments by measuring the intensity of $\gamma$-rays scattered through small angles from a copper plate. The results are compared to flux determinations derived from strong narrow resonances with known scattering cross sections in various nuclides in $\gamma$-ray scattering experiments. [Preview Abstract] |
Saturday, April 12, 2008 2:30PM - 2:42PM |
D14.00006: Design and Performance of Neutron Detector N* Iwona Pawelczak, Jan T\~oke, Yun-Tse Tsai, W. Udo Schr\"oder The design of the N* Detector (``Neutron Sandwich Transmuter/Activation-$\gamma $ Radiator'') and its response to neutrons are described. The N* is a high efficiency plastic-scintillation detector with sensitivity to neutrons in a wide energy range and multi-hit information. The device consists of a stack of plastic scintillator slabs (Saint Gobain BC-408) alternating with thin radiator films (PDMS), which are loaded with 0.5{\%} (by weight) of Gd. The stack is coupled to a photomultiplier tube. The scintillator plays the dual role of a neutron moderator and a $\gamma $-radiation detector. Scintillation light is produced in response to both, the prompt moderation process and the delayed emission of Gd-capture $\gamma $-rays. The design and experimental results with respect to light response, energy and time resolution, and detection efficiency will be discussed, along with comparison to Monte Carlo simulations. [Preview Abstract] |
Saturday, April 12, 2008 2:42PM - 2:54PM |
D14.00007: The commissioning of the O-TPC at TUNL P.-N. Seo, M.W. Ahmed, E.R. Clinton, C.R. Howell, S.C. Stave, H.R. Weller, A.H. Young, M. Gai, B. Bromberger, V. Dangendorf, K. Tittelmeier We are commissioning the Optical Readout Time Projection Chamber (O-TPC) that will be used in an experiment at the HIgS facility at TUNL for studying oxygen formation during stellar helium burning by studying the time reversed $^{16}{\rm O}(\gamma,\alpha)^{12}{\rm C}$ reaction. The initial calibration of the O-TPC was carried out at the LNS at Avery Point with a CMAC based data acquisition system. The tests at TUNL used a VME based data acquisition system that also controls a CCD camera. Under stable conditions an energy resolution as good as 2.6\% was measured for the charge signal and single and double tracks of alpha particles from a $^{148}{\rm Gd}$ source were recorded in the CCD camera. These tracks were analyzed using an automated pattern recognition algorithm that allows us to extract that track centroid (from which the scattering angle is deduced) as well as DE/DX along the track. The azimuthal angle of the track is deduced from the Time Projection. The O-TPC is found to be ready for accepting beams from the HIgS facility. [Preview Abstract] |
Saturday, April 12, 2008 2:54PM - 3:06PM |
D14.00008: Laser-Induced Fluorescence Detection of He$_2$ Molecules in Superfluid Helium as a New Detector Technology W.G. Rellergert, S.B. Cahn, A. Curioni, J.A. Nikkel, J.D. Wright, D.N. McKinsey Ionizing radiation events in liquid helium result in the copious production of long-lived He$_2$ triplet molecules ($\tau$ = 13 s). We present results on the detection and imaging of these molecules in superfluid helium using laser-induced fluorescence. We show that a laser tuned to 905 nm can excite the molecules via a two photon transition which results in the emission of detectable red photons at 640 nm. Upon deexcitation, molecules return to their ground triplet state, and can be excited again. This cycling transition can be repeated many times during the lifetime of the molecule, potentially enough times to allow for single molecule detection. We present emission and absorption spectra and show images obtained using an intensified CCD camera. This technique gives rise to a new detector technology with applications in the detection of gamma rays, WIMP dark matter, and ultracold neutrons. [Preview Abstract] |
Saturday, April 12, 2008 3:06PM - 3:18PM |
D14.00009: Monte Carlo studies of $\beta$-detector efficiency with GEANT4 for precise $\beta^+$-branching-ratio experiments V.V. Golovko, V.E. Iacob, J.C. Hardy We previously reported Monte Carlo (MC) studies of the efficiency of a 1-mm-thick plastic detector to few-MeV electrons with various programs: Geant4, EGSnrc and Penelope. The simulated results were also compared with measured data from standard conversion-electron sources: $^{133}$Ba, $^{137}$Cs and $^{207}$Bi.~[1] These studies were part of our program to test the Electroweak Standard Model via precise measurements of lifetimes, branching ratios and Q-values of superallowed $0^+\rightarrow0^+$ nuclear transitions~[2], which in turn yield the value of the up-down quark-mixing element of the Cabibbo-Kobayasshi-Maskawa (CKM) matrix. The MC studies of the $\beta$-detector efficiency are important for the measurement of precise $\beta^+$-branching-ratios since there is a slight difference in the efficiency of the $\beta$-detector for different $\beta$-branches. This has an additional affect on the number of observed $\beta-\gamma$ coincidences over and above the well known efficiency of our $\gamma$-ray detector. We report here an extension of the comparison between MC calculations and experiment to a $^{60}$Co $\beta$-source, and a study of the influence of peripheral objects on the $\beta$-detector efficiency. [1]~V.V.~Golovko \textit{et. al.} \newblock {\em BAPS 59}, no~6, p.~DH4 83, 2006; \newblock {\em BAPS 52}, no~3, p.~C16 53, 2007; \newblock {\em BAPS 52}, no~9, p.~EH8 83, 2007. [2]~J.C.~Hardy and I.S.~Towner. \newblock {\em PRC}, 71(5):055501, 2005. [Preview Abstract] |
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