Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session Y13: Instrumentation II |
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Sponsoring Units: DNP Chair: Sean Stave, Pacific Northwest National Laboratory Room: Plaza Court 2 |
Tuesday, April 16, 2013 1:30PM - 1:42PM |
Y13.00001: Projectile influence on production cross section for $^{48}$Ca-, $^{50}$Ti-, and $^{54}$Cr- induced fusion-evaporation reactions D.A. Mayorov, T.A. Werke, M.C. Alfonso, M.E. Bennett, C.M. Folden III Evaporation residue excitation functions for $^{48}$Ca, $^{50}$Ti $+$ $^{159}$Tb and $^{48}$Ca, $^{54}$Cr $+ \quad^{162}$Dy were measured at Texas A{\&}M University using the vacuum spectrometer MARS. The produced residues are weakly deformed nuclei near the $N =$ 126 shell closure. However, the production cross sections are insensitive to the associated shell stabilization to the fission barrier, an observation previously reported in literature. The ratio of maximum production cross sections between the $^{48}$Ca/$^{50}$Ti and $^{48}$Ca/$^{54}$Cr reactions is $\approx $ 47 and \textgreater 7100, respectively. These substantial differences can be reproduced in theoretical calculations by inclusion of collective enhancements during de-excitation of the compound nucleus. The competition between quasifission and complete fusion further contributes to the observed separation in the excitation functions. Model-dependent estimates of the compound nucleus formation probability, $P_{CN}$, yield ratios of $P_{CN}(^{48}$Ca $+ \quad^{159}$Tb) / $P_{CN}(^{50}$Ti $+ \quad^{159}$Tb) $\approx $ 2.5 and $P_{CN}(^{48}$Ca $+ \quad^{162}$Dy) / $P_{CN}(^{54}$Cr $+$ $^{162}$Dy) $\approx $ 5. Heavy-ion fusion reactions with $^{48}$Ca, $^{50}$Ti, and $^{54}$Cr projectiles are of interest due to modern-day efforts to synthesize superheavy elements 119 and 120 in warm fusion reactions with projectiles having $Z$ \textgreater 20. [Preview Abstract] |
Tuesday, April 16, 2013 1:42PM - 1:54PM |
Y13.00002: Effects of Odd-$Z$ Projectiles on Fusion-Evaporation Cross Sections Tyler Werke, Dmitriy Mayorov, Marisa Alfonso, Megan Bennett, Michael DeVanzo, Charles Folden III The production of nuclides near the $N=$126 shell in the $^{45}$Sc $+ \quad^{159}$Tb, $^{162}$Dy reactions has been studied at Texas A{\&}M University using the MARS spectrometer. Previously measured 4n exit channel cross sections for the $^{48}$Ca, $^{50}$Ti $+ \quad^{159}$Tb and $^{48}$Ca $+ \quad^{162}$Dy reactions have exhibited enhanced fission probabilities in the de-excitation of the compound nucleus due to collective enhancements to the fission level density. The current research intends to study the change in the evaporation residue cross sections when odd-$Z$ projectiles react with the same targets. The maximum 4n cross sections of the $^{45}$Sc $+$ $^{159}$Tb, $^{162}$Dy reactions were 2 $\mu $b, and 4 $\mu $b respectively, and these data are several orders of magnitude smaller than both theoretical predictions and the experimental data for the $^{48}$Ca and $^{50}$Ti reactions discussed above. This can be explained by collective enhancements as well as the relative neutron deficiency of $^{45}$Sc compared to $^{48}$Ca and $^{50}$Ti. This talk will discuss theoretical models of evaporation residue cross sections, and will discuss the latest results on excitation functions for odd-$Z$ projectiles reacting with lanthanide targets. This work may also have relevance to the production of superheavy elements with Z \textgreater\ 118. [Preview Abstract] |
Tuesday, April 16, 2013 1:54PM - 2:06PM |
Y13.00003: Detector Design for the sPHENIX Hadronic Calorimeter Shawn Beckman The sPHENIX detector proposal, for precision jet measurements in heavy ion collisions at RHIC, requires a large coverage hadronic calorimeter. The design must be compact and incorporate the magnetic field flux return, thus requiring the electronics to operate in a magnetic field. The current design incorporates alternating plates of steel and plastic scintillator, with embedded wavelength shifting fiber optics to transmit photons to silicon photomultipliers (SiPMs). Our goal is to optimize the light collection and ensure uniform light yield in the prototype hadronic calorimeter. We report on tests involving embedding fiber optics, light collection into SiPMs, and uniformity testing of scintillator panels. [Preview Abstract] |
Tuesday, April 16, 2013 2:06PM - 2:18PM |
Y13.00004: The Barrel Calorimeter for the GlueX Experiment at Jefferson Lab Zisis Papandreou The GlueX experiment at Jefferson Lab will search for exotic hybrid mesons as evidence of gluonic excitations, in an effort to understand confinement in QCD. The key features of this compelling physics program will be presented together with an overview of the detector, focusing on the electromagnetic barrel calorimeter (BCAL). The BCAL is a ``spaghetti calorimeter,'' consisting of layers of corrugated lead sheets, interleaved with planes of 1-mm-diameter, double-clad, scintillating fibres, bonded in the lead grooves using optical epoxy. This detector will consist of 48 modules and will be readout using 3,840 large-area Multi-Photon Pixel counter arrays. The experiment is now in the installation phase with data taking expected in 2015. [Preview Abstract] |
Tuesday, April 16, 2013 2:18PM - 2:30PM |
Y13.00005: Status of the construction of the Gluex Forward Drift Chambers Simon Taylor Currently under construction at the Thomas Jefferson National Accelerator Facility in Newport News, Virginia, the full GlueX detector is designed to study gluonic degrees of freedom through the production of ``hybrid'' mesons with exotic quantum numbers. To accomplish this task the detector requires high acceptance and reasonably good resolution for both charged and neutral particles. The core of the detector is housed within the bore of a 2.0 Tesla solenoidal magnet. Charged particles emanating from the target for angles greater than about 20 degrees with respect to the beam line will be tracked with a straw-tube detector (the Central Drift Chamber). Forward-going charged particles will be detected using the Forward Drift Chambers (FDC). I will describe the design and construction of the FDC and present preliminary resolution measurements. [Preview Abstract] |
Tuesday, April 16, 2013 2:30PM - 2:42PM |
Y13.00006: Characteristics of S12045(X) photon sensors for GlueX E.S. Smith, Y. Qiang, I. Tolstukhin, W.K. Brooks, H. Hakobyan, S. Kuleshov, O. Soto, A. Toro The barrel calorimeter of the GlueX detector in Hall D at Jefferson Lab will be instrumented with 4000 large-area (1.2$\times$1.2 cm$^2$) silicon photomultipliers (SiPMs) [1]. These photon sensors have properties similar to vacuum photomultipliers, but are unaffected by high magnetic fields. In our experiment, they will operate in magnetic fields exceeding 1\,T. After extensive tests with a variety of sensors, we chose the S12045(X) custom SiPM arrays manufactured by Hamamatsu Corporation, also known as multi-pixel photon counters (MPPCs) [2]. All production units have been delivered and we have measured the photon detection efficiency (PDE), gain, dark rate, cross talk and after pulsing at three different temperatures (5, 7 and {20$^\circ$C}). We will present a summary of these measurements and the plan for use of these sensors in the GlueX experiment.\\[4pt] [1] F. Barbosa {\em et al.,} NIM A695 (2012) 100.\\[0pt] [2] Y. Qiang {\em et al.,} NIM A698 (2013) 234. [Preview Abstract] |
Tuesday, April 16, 2013 2:42PM - 2:54PM |
Y13.00007: Simulation and Analysis of Neutron Activation Risk for the IsoDAR High-Intensity Electron Antineutrino Source Michael Skuhersky IsoDAR (Isotope Decay-At-Rest) is a proposed high-intensity source of electron antineutrinos intended for use in searches for beyond standard model physics, the main analysis being a short baseline search for sterile neutrinos at a kiloton scale liquid scintillator detector. The source uses a compact cyclotron to deliver 600kW of protons at 60 MeV/nucleon in the form of $H_{2}^{+}$ onto a Beryllium target which produces a large intermediate energy neutron flux. These neutrons thermalize and capture on a 99.9\% pure $^{7}Li$ sleeve, which produces $^{8}Li$ at rest, which subsequently beta decays producing $\bar{\nu }_{e}$. Due to the high neutron fluxes, large duty factor, and low background environment surrounding the neutrino detector, we need to understand the activation risk and design a shield to minimize this risk allowing for the safe operation of the source. I will report on my neutron activation studies and the benchmarking of Geant4 for these applications. [Preview Abstract] |
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