Bulletin of the American Physical Society
2015 Fall Meeting of the APS Division of Nuclear Physics
Volume 60, Number 13
Wednesday–Saturday, October 28–31, 2015; Santa Fe, New Mexico
Session KF: Instrumentation III |
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Chair: Mitch Allmond, Oak Ridge National Laboratory Room: Lamy |
Friday, October 30, 2015 2:00PM - 2:12PM |
KF.00001: A dedicated ion trap at CARIBU for beta-delayed neutron spectroscopy Barbara Wang, N.D. Scielzo, E.B. Norman, G. Savard, J.A. Clark, A.F. Levand, A. Aprahamian, M. Burkey, S. Caldwell, A. Czeszumska, S.T. Marley, G.E. Morgan, A. Nystrom, R. Orford, S.W. Padgett, A. Perez Galvan, K.S. Sharma, K. Siegl, S. Strauss Trapped radioactive ions suspended in vacuum allow for a new way to perform beta-delayed neutron spectroscopy. Decay branching ratios and energy spectra of the emitted neutrons are inferred from a measurement of the nuclear recoil, thereby circumventing the many limitations associated with direct neutron detection. Plans for the development of a dedicated ion trap for experiments using the intense fission fragment beams from the Californium Rare Isotope Breeder Upgrade (CARIBU) facility at Argonne National Laboratory are summarized. The trap design has been guided by experience gained from recent ion-trap experiments measuring \textsuperscript{137-138,140}I, \textsuperscript{134-136}Sb, and \textsuperscript{144-145}Cs. The improved nuclear data that can be collected are needed in many fields of basic and applied science such as nuclear energy, nuclear astrophysics, and stockpile stewardship. [Preview Abstract] |
Friday, October 30, 2015 2:12PM - 2:24PM |
KF.00002: FIONA: A new mass analyzer for superheavy elements Nicholas Esker, Jacklyn Gates, Gregory Pang, Kenneth Gregorich Six new superheavy elements ($Z=113-118$) and over fifty new transactinide isotopes ($Z>104$) have been synthesized in compound nuclear fusion reactions using ${}^{48}$Ca beams on actinide targets in the last 15 years. These superheavy elements (SHE) are short-lived and their decay chains end before reaching nuclides with unambiguously determined $Z$ or $A$. At the LBNL 88'' Cyclotron, we use the Berkeley Gas-Filled Separator (BGS) to study the production and decay of SHE produced at rates of a few atoms per week. The BGS's high beam suppression comes with poor mass resolution and detection is hindered by the high background rates from the proximity to the target and beamstop. Ongoing upgrades to the BGS, including product thermalization and transport, will allow us to couple a mass analyzer to the BGS. Known as FIONA (Fast Identification Of Nuclide $A$), the analyzer is a mass separator designed for 100\% transmission with an expected mass resolution of $2000 $A/$\Delta$ A. These upgrades will greatly increase sensitivity by delivering mass-separated superheavy element nuclei to a low-background detector system on a 10-ms timescale. The current progress in commissioning the FIONA mass analyzer and the future directions of the project will be presented. [Preview Abstract] |
Friday, October 30, 2015 2:24PM - 2:36PM |
KF.00003: New separators at the ATLAS facility Birger Back Two new separators are being built for the ATLAS facility. The Argonne Gas-Filled Analyzer (AGFA) is a novel design consisting of a single quadrupole and a multipole magnet that has both dipole and quadrupole field components. The design allows for placing Gammasphere at the target position while providing a solid angle of $\sim$ 22 msr for capturing recoil products emitted at zero degrees. This arrangement enables studies of prompt gamma ray emission from weakly populated trans-fermium nuclei and those near the doubly-magic N$=$Z$=$50 shell closure measured in coincidence with the recoils registered by AGFA. The Argonne In-flight Radioactive Ion Separator (AIRIS) is a magnetic chicane that will be installed immediately downstream of the last ATLAS cryostat and serve to separate radioactive ion beams generated in flight at an upstream high intensity production target. These beams will be further purified by a downstream RF sweeper and transported into a number of target stations including HELIOS, the Enge spectrograph, the FMA and Gammasphere. This talk will present the status of these two projects. [Preview Abstract] |
Friday, October 30, 2015 2:36PM - 2:48PM |
KF.00004: Development of a high-rate ion counter for particle identification with GODDESS Travis Baugher, J.A. Cizewski, A. Ratkiewicz, M. Febbraro, S.D. Pain, K.L. Jones, K. Smith Transfer reactions in inverse kinematics can provide a wealth of data on the structure of exotic nuclei. Gammasphere-ORRUBA Dual Detectors for Experimental Structure Studies (GODDESS) consists of the Oak Ridge-Rutgers University Barrel Array (ORRUBA) of position-sensitive silicon detectors placed inside the Gammasphere target chamber. GODDESS enables particle-gamma coincidence measurements to be performed for inelastic, stripping and pickup reactions with high resolution and high efficiency. Experiments performed in inverse kinematics result in heavy-ion recoils at very forward angles. Detecting and identifying these recoils with high efficiency and low dead time is crucial for experiments, in particular experiments with contaminated beams. An ionization chamber has been incorporated into the GODDESS setup to count and identify recoiling heavy ions. The gas-filled, gridded ionization chamber was developed, built and tested at Oak Ridge National Laboratory and with first in-beam tests during the GODDESS commissioning experiment at Argonne National Laboratory. Preliminary results will be presented. This work was supported in part by the U.S. Department of Energy and National Science Foundation. [Preview Abstract] |
Friday, October 30, 2015 2:48PM - 3:00PM |
KF.00005: Hybrid Array of Gamma Ray Detectors (HAGRiD) Karl Smith, R. Grzywacz, K.L. Jones, S. Munoz, T. Baugher, J.A. Cizewski, A. Ratkiewicz, S.D. Pain Transfer reactions and beta-decay studies are powerful tools to study nuclear structure and to provide insight into astrophysically important reactions that may be difficult to measure directly. Both types of studies are enhanced immensely by measuring a particle-gamma coincidence. For transfer reactions, gamma-ray measurements improve the resolution, aid in channel selection and lifetime measurements. To achieve these coincidences the Hybrid Array of Gamma Ray Detectors (HAGRiD) is being designed and constructed. This array would be coupled with the Oak Ridge Rutgers Barrel Array (ORRUBA) of silicon detectors, the Versatile Array of Neutron Detectors at Low Energy (VANDLE) and beta detection scintillators. Detector systems providing a particle-gamma coincidence have previously compromised the charged-particle angular resolution due to compact geometries used to increase the gamma efficiency. HAGRiD will be coupled with ORRUBA such that resolution is not sacrificed, requiring the new array to provide improved resolution and efficiency over NaI and increased portability and flexibility over germanium detectors; therefore, we have chosen to use LaBr$_3$(Ce) crystals. We demonstrate the advantages of a coupled detector system and discuss the current status of the project. [Preview Abstract] |
Friday, October 30, 2015 3:00PM - 3:12PM |
KF.00006: Development of a neutron long-counter system for astrophysical ($\alpha,xn$) reaction studies Sunghoon Ahn, Fernando Montes, Wei Jia Ong, Zachary Meisel, Jesus Perello Recent studies on the discrepancy of $Z$ = 38 - 47 abundances between metal poor stars have proposed $(\alpha,xn)$ reactions as the main reaction pathway for early nucleosynthesis in the wind with the condition of $(n,\gamma)-(\gamma,n)$ equilibrium and temperatures between 3.5 and 5.5~GK. Uncertainties in $(\alpha,xn)$ reaction rates directly affect calculated abundances with an impact that is comparable to that from astrophysical uncertainties. At present, reaction rate uncertainties are relatively large since little experimental data exists for $(\alpha,xn)$ cross sections involved in the nucleosynthesis calculation. We are developing a neutron detector which counts emitted neutrons from the $(\alpha,xn)$ reactions. The detector consists of 80 gas-filled BF$_3$ and $^3$He proportional tubes oriented in rings along the beam axis embedded in a polyethylene matrix. The configuration of the tubes in the matrix is determined by both a high average neutron detection efficiency and the efficiency as a function of energy to be as constant as possible from $E_n = 0.1$-$19.5$~MeV, since neutron energy information will be lost due to neutron moderation. Details of the detector design and a status report on the device will be presented. [Preview Abstract] |
Friday, October 30, 2015 3:12PM - 3:24PM |
KF.00007: Simulating the growth of an charge cloud for a microchannel plate detector Davinder Siwal, Blake Wiggins, Romualdo deSouza Position sensitive microchannel plate (MCP) detectors have a variety of applications in the fields of astronomy, medical imaging, neutron imaging, and ion beam tracking. Recently, a novel approach has been implemented to detect the position of an incident particle. The charge cloud produced by the MCP induces a signal on a wire harp placed between the MCP and an anode. On qualitative grounds it is clear that in this detector the induced signal shape depends on the size of the electron cloud. A detailed study has therefore been performed to investigate the size of the charge cloud within the MCP and its growth as it propagates from the MCP to the anode. A simple model has been developed to calculate the impact of charge repulsion on the growth of the electron cloud. Both the details of the model and its predictions will be presented. [Preview Abstract] |
Friday, October 30, 2015 3:24PM - 3:36PM |
KF.00008: Development of a novel position-sensitive microchannel plate detector Blake Wiggins, Davinder Siwal, Romualdo deSouza Position sensitive microchannel plate (MCP) detectors which measure the position of an incident electron, ion, or photon, are useful in imaging applications. Recently, a novel detector, which utilizes an induced approach to provide position sensitivity, has been developed.\footnote{Using induced signals to sense position from a microchannel plate detector, R. T. deSouza, Z. Q. Gosser, and S. Hudan, Rev. Sci. Instrum. 83, 053305 (2012).} In the prototype detector, using only the zero-crossing point of the inherently bipolar signals, a position resolution of 466 $\mu$m (FWHM) has been achieved. Implementing a differential readout may improve on this resolution. To realize this differential approach, a better understanding of the dependence of the induced signal shape on the position of the electron cloud is required. To characterize the dependence of the induced signal shape on position a resistive anode (RA) has been incorporated into the detector. The RA will allow determination of the centroid of the electron cloud. Factors impacting the position resolution obtained with the RA will be discussed and the achieved position resolution of 157 $\mu$m (FWHM) will be presented. [Preview Abstract] |
Friday, October 30, 2015 3:36PM - 3:48PM |
KF.00009: Transfer reactions with JENSA: study of the levels in $^{12}$N using $^{14}$N(p,t) K.A. Chipps The Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas jet target, recently recommissioned in the ReA3 facility at the NSCL, will provide a state-of-the-art, dense, localized, and pure target of light, gaseous elements for various reaction studies. As one of a series of commissioning physics measurements to demonstrate the benefit of the new Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas jet target for enabling next-generation transfer reaction studies, the $^{14}$N(p,t)$^{12}$N reaction was studied using a pure 300 psig jet of nitrogen, in order to help elucidate the structure of $^{12}$N. The experiment and lessons learned for future gas jet transfer reaction measurements will be discussed. [Preview Abstract] |
Friday, October 30, 2015 3:48PM - 4:00PM |
KF.00010: A large surface detector for ultracold neutrons C.L. Morris, Zhehui Wang A multilayer surface detector for ultracold neutrons (UCNs) that was recently demonstrated will be described. The detector consisted of a top $^{10}$B layer around 100 nm thick, a ZnS(Ag) scintillator layer of a few micron thick and a photodetector with a sensitivity down to single photons. Electron-beam evaporation was used to deposit $^{10}$B onto commercial ZnS(Ag) coated screens. We are extending the concept to a double-sided large surface (20 cm $\times$ 40 cm) detector for UCN counting in the UCNtau magnetic trap. To minimize the number of photodetectors and readout channels, the scintillator light from the ZnS(Ag) is collected using an array of wavelength shifting fibers. The light loss as a function of position is characterized using a $^{148}$Gd alpha source. The detection efficiency as a function of surface roughness is discussed. The detector will be used in the upcoming UCN experiments at the LANSCE UCN facility. [Preview Abstract] |
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