Bulletin of the American Physical Society
2007 Annual Meeting of the Division of Nuclear Physics
Volume 52, Number 10
Wednesday–Saturday, October 10–13, 2007; Newport News, Virginia
Session EH: Instrumentation I |
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Chair: Steven D. Pain, Oak Ridge National Laboratory Room: Newport News Marriott at City Center Blue Point I |
Friday, October 12, 2007 2:00PM - 2:12PM |
EH.00001: A TPC with optical readout for directional detection of dark matter Hidefumi Tomita, Steve Ahlen, Denis Dujmic, Peter Fisher, Asher Kaboth, Jocelyn Monroe, Gabriella Sciolla, Hermann F. Wellenstein, Richard Yamamoto A TPC with optical readout has been developed with the goal of detecting the sense and direction of the elastic recoils generated by Dark Matter interactions. The detector, filled with CF4 gas at low pressure, was placed in a low-energy neutron beam and used to record the scintillation light created by the recoiling gas nuclei. The variation of the light intensity observed along the track is due to the decreasing ionization rate. This effect, known as the ``head-tail'' effect, allows us to determine the direction of the incoming neutrons. [Preview Abstract] |
Friday, October 12, 2007 2:12PM - 2:24PM |
EH.00002: Testing Novel, Position-Sensitive Detectors with Alpha-Gamma Angular Correlations S. Lakshmi, P. Chowdhury, S.K. Tandel, C.M. Wilson, S. Gros, C.J. Lister, R. Farrel, M. McClish, K.S. Shah We report on our tests of novel, position-sensitive particle and gamma detectors for applications in nuclear physics experiments. We measure the angular correlation between the alpha particle decay of $^{224}$Ra to an excited state in $^{220}$Rn, and the subsequent gamma decay to the ground state in $^{220}$Rn using a 25 mm$^{2}$, $<$200 micron thick position-sensitive avalanche photo-diode (PSAPD) for detecting the alpha particles and a 20 mm thick, 14x14 planar germanium double-sided strip detector (GeDSSD) for detecting the gamma rays. A large solid angle can be covered in a single, fixed geometry, given the excellent position resolution of the PSAPD (400 microns) and the GeDSSD (5 mm) by positioning the detectors close to the source. Improved distortion correction algorithms for the PSAPD, pixel efficiencies, method of angle reconstruction and the measured angular correlation will be presented. [Preview Abstract] |
Friday, October 12, 2007 2:24PM - 2:36PM |
EH.00003: Performance evaluation of novel square-bordered position-sensitive silicon detectors with four-corner readout A. Banu, Y. Li, M. McCleskey, C.A. Gagliardi, L. Trache, R.E. Tribble, M. Bullough, S. Walsh, C. Wilburn A new square-bordered type two-dimensional position sensitive silicon detector produced by Micron Semiconductor Ltd. was recently developed in collaboration with Cyclotron Institute at Texas A{\&}M University. It consists of a square-shaped ion-implanted resistive anode framed by an additional square low resistivity strip. The main characteristics of the detectors are given and $\alpha $-particle as well as in-beam measurements concerning detector operational parameters such as response to position linearity, position and energy resolutions are presented. Experimental results obtained in beam show a position resolution below 1 mm (FWHM) and a very good non-linearity of less than 1 {\%} (rms). [Preview Abstract] |
Friday, October 12, 2007 2:36PM - 2:48PM |
EH.00004: Neutron Multiplicity Discrimination in MoNA W.F. Rogers, J. Gillette, M. Gardner, A. Reed, S. Mosby The Modular Neutron Array (MoNA) is a high-efficiency neutron detector at the National Superconducting Cyclotron Laboratory at MSU, used in conjunction with the NSCL/FSU sweeper magnet to investigate the loss of one or more neutrons from particle-unbound nuclei near and beyond the neutron drip-line. In order to properly analyze data from these experiments it is important to distinguish neutron multiplicity in MoNA. We've developed an algorithm that produces scatter plots of neutron velocity change vs. scattering angle and energy deposition vs. scattering angle, each of which results in a locus of events corresponding (largely) to single neutron multiple-scatter events, and each of which can be used to gate the other for cross-correlation. Challenges to accurate neutron trajectory mapping include sub-threshold neutron scattering from carbon (which changes neutron trajectories in unpredictable ways) and the discrete nature of the array, which (especially for shorter scattering lengths) results in scattering angles not necessarily reflective of actual neutron trajectories. Results for experiments involving one and two neutron decays will be presented. [Preview Abstract] |
Friday, October 12, 2007 2:48PM - 3:00PM |
EH.00005: Development of a neutron detector with broad dynamic range and multi-hit capability Iwona Pawelczak, Jan T\~oke, Yun-Tse Tsai, W. Udo Schr\"oder A new type of Gd-loaded plastic neutron detector with a broad dynamic range (from thermal to MeV range) and multi-hit capability has been designed and subjected to series of tests. The device consists of a stack of alternating plastic scintillator (Saint Gobain BC-408) slabs and thin radiator films (PDMS -- SYLGARD 184) loaded with 0.5{\%} of Gd per weight, viewed by a photomultiplier tube. The scintillator functions as neutron moderator, provides a prompt integrated neutron energy signal, and detects delayed n capture by Gd nuclei via associated capture $\gamma $-rays. The design, Monte Carlo simulations carried out with an extended code DENIS(E), as well as first measurements with the detector will be discussed. [Preview Abstract] |
Friday, October 12, 2007 3:00PM - 3:12PM |
EH.00006: Design Study of DESCANT - DEuterated SCintillator Array for Neutron Tagging James Wong, P.E. Garrett The fusion-evaporation reaction has been a useful tool for studying nuclei. A program of such reactions is being planned to take place at the TRIUMF facility in Vancouver, Canada using the TIGRESS array of gamma-ray detectors. A particular advantage of using these reactions is that they probe nuclei at moderate-to-high angular momenta. It would be of great interest to extend the study of high-spin states to neutron-rich systems. Following the formation of the fused compound system, the highly-excited state may lose energy by ``evaporating'' particles. Neutron evaporation is the predominant decay mode from neutron-rich compound systems so neutron detectors will be required. The probability of neutrons multiple scattering is quite high so a detector array must be able to differentiate between multiple neutrons evaporating from the reaction and a single neutron scattering multiple times. To address this issue we investigate the use of a novel neutron detector array -- one based on an array of deuterated liquid scintillators as neutron detectors. Results from early feasibility tests will be presented, along with the status of our GEANT4 simulations of the array performance. [Preview Abstract] |
Friday, October 12, 2007 3:12PM - 3:24PM |
EH.00007: Investigation of Plastic Scintillator Detector Configurations for Neutron Studies Catalin Matei, D.W. Bardayan, J.C. Blackmon, J.A. Howard, J.A. Cizewski, P.D. O'Malley, S.D. Pain, W.A. Peters, R.K. Grzywacz, K.L. Jones, S.N. Liddick Plastic scintillation products are widely used for detecting nuclear radiation. Measurements of the response of plastic scintillator detectors to different radiations are important in the design phase of a detection system and as an initial input in Monte Carlo simulation codes. We performed test measurements of the light response, attenuation length, time and position resolution, and detection efficiency of Bicron BC408 plastic scintillator. Four plastic scintillator bars of dimensions 2.9$\times$2.9$\times$60 cm$^{3}$ and 5$\times$5$\times$200 cm$^{3}$ have been developed to be used in (d,n) and beta-delayed neutron studies. The detectors were constructed with different reflecting materials, optical couplings and photomultiplier tube assemblies. Measurements are compared with predictions from the Monte Carlo simulation code GEANT4. Details of the experimental configuration and results will be presented. [Preview Abstract] |
Friday, October 12, 2007 3:24PM - 3:36PM |
EH.00008: Comparison of various Monte Carlo for response-function studies of a plastic $\beta$-detector used in precise $\beta^+$-branching-ratios experiments V.V. Golovko, V.E. Iacob, J.C. Hardy, D. Melconian In order to test the Conserved Vector Current hypothesis of the Standard Model, precise determination of the branching ratios for superallowed $\beta$ transitions is needed~[1]. For this purpose, we are using an experimental setup in which one of the main components is a plastic scintillator, and a knowledge of the Response Function (RF) of this scintillator to $\beta$ particles as a function of energy is important. In previous works we compared a Monte Carlo (MC) simulated RF with experiment for $\beta$-particles from standard $\beta$-sources as well as from ``on-line" measurements~[2]. However, we found that various MC programs predict slightly different results. To investigate this, we created the simplified configurations for the MC programs and studied the RF of a plastic disk to monoenergetic positrons with different energies from a point-like source in the air. We concentrated on an intercomparison between the MC results from physics models of various codes: Geant4, Penelope and EGSsrc. For energies between 0.1~MeV to 20~MeV, we see 2\% relative differences in the efficiency calculations from different programs. [1]~J.C.~Hardy and I.S.~Towner. \newblock {\em PRC}, 71(5):055501, 2005. [2]~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. [Preview Abstract] |
Friday, October 12, 2007 3:36PM - 3:48PM |
EH.00009: A Novel Optics Design for Laser Polarized $^3$He Targets Jaideep Singh, Vladimir V. Nelyubin, Scott T. Rohrbaugh, W. Al Tobias, Gordon D. Cates Laser polarized $^3$He targets using spin-exchange optical pumping (SEOP) are used for studying nucleon spin structure and neutron form factors, among other things. Optical pumping requires several watts of laser light which is supplied by multiple fiber-coupled laser diode arrays. Traditionally, each of these lasers required its own set of optics to collimate and circularly polarize the beam. This resulted in several beam lines with large angular offsets from the central beam line which limit the efficiency of optical pumping. We present a compact design using just one set of optics which takes advantage of a 5 to 1 fiber optic combiner. Upto 5 lasers can be connected to a combiner which ultimately results in just two nearly parallel beam lines. Another advantage is the easily adjustable size of the beam spot on the target. This design has already been successfully implemented in our lab and in the Jefferson Lab Hall A polarized $^3$He target. We also discuss an analysis of the design including a detailed optical pumping simulation used to motivate the design parameters. [Preview Abstract] |
Friday, October 12, 2007 3:48PM - 4:00PM |
EH.00010: First Use of Novel Techniques for Polarized $^3$He Targets Aidan Kelleher Spin-exchange optically pumped (SEOP) $^3$He targets have been successfully used in Hall A at Jefferson Lab as an effective polarized neutron target. Design requirements for E02-013 (Measurement of Sachs form factor $G_E^n$ at high $Q^2$) and a recent breakthrough in SEOP target cells suggested several changes to the target. SEOP targets use an optically pumped alkali metal to polarize a noble gas. E02-013 was the first electron scattering target to make use of an alkali metal mixture in place of a single alkali metal. These hybrid cells had a faster polarization time, and a higher overall $^3$He polarization. The result was a record in-beam polarization for an SEOP polarized $^3$He target. Previous SEOP targets in Hall A used a holding field supplied by a set of open Helmholtz coils. E02-013 used a magnetic box to provide a uniform magnetic field and to shield the target from the stray magnetic fields produced by the large acceptance open spectrometer placed close to the magnet. Several small polarimetry improvements were made. Innovations were also made to the measurements of the direction and homogeneity of the main holding field. These improvements will be discussed. [Preview Abstract] |
Friday, October 12, 2007 4:00PM - 4:12PM |
EH.00011: TITAN Penning Trap mass spectrometer: design, commissioning and the near future. Vladimir Ryjkov, Maxime Brodeur, Jens Dilling TITAN facility is designed to use a variety of ion trapping techniques to conduct nuclear and atomic physics research. It will be used to study short-lived isotopes produced by the ISAC RIB source at TRIUMF National Laboratory in Vancouver, Canada. One of the components of the TITAN facility is the precision Penning trap mass spectrometer. It is now being commissioned and is scheduled for its first online mass measurement at the end of August of 2007. An overview of the TITAN Penning trap mass spectrometer design will be given. The preliminary results of the commissioning run will be described and the short-term measurement goals will be outlined. [Preview Abstract] |
Friday, October 12, 2007 4:12PM - 4:24PM |
EH.00012: Solid State Photomultipliers for Nuclear and High Energy Experiment Applications. Erik Johnson, Skip Augustine, Radia Sia, Christopher Stapels, James Christian Solid-State Photomultipliers (SSPMs) are an array of photodiodes built on a common substrate. Each photodiode is operated in a Geiger mode, where a single photon could trigger a self-sustained avalanche. The avalanche is quenched either using passive quenching or active quenching circuits (both methods will be discussed). The avalanche provides a gain of $\sim $10$^{6}$, which is comparable to existing photomultiplier tubes. Radiation Monitoring Devices has built SSPMs with CMOS processes, which allows for integrating signal processing and photon collection on one chip, allowing for a detector-on-a-chip design. A number chip designs will be presented showing the potential of these devices for various applications for nuclear and high-energy experiments. [Preview Abstract] |
Friday, October 12, 2007 4:24PM - 4:36PM |
EH.00013: Solid-State Photomultipliers Operated In Extreme Experimental Conditions. Erik Johnson, Skip Augustine, Christopher Stapels, Radia Sia, James Christian Nuclear and high-energy physics experiments that are conducted in harsh environments, such as in a liquid nitrogen bath, a high magnetic field of several Tesla, a small physical region of a few centimeters, a high intensity radiation field of hundreds of mrad/hour, require improved sensors that operate in these conditions. Advances in detector technology used in extreme environments can improve the data quality and allow new designs for experiments that operate under these conditions. Solid-State Photomultipliers (SSPM), a device built from an array of photodiodes, is a compact, high-gain photodetector with insensitivity to low temperatures, high radiation fields, and strong magnetic fields. Radiation Monitoring Devices has built SSPMs with CMOS processes, which allows for integrating signal processing and photon collection on one chip, allowing for a detector-on-a-chip design. SSPMs were exposed to 26 rads of dose from beams of 1 GeV/n silicon nuclei and 1 GeV protons, low temperature conditions from 77 K to 4 K, and high magnetic fields around 1 Tesla. The SSPMs were characterized under these extreme conditions. [Preview Abstract] |
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