Bulletin of the American Physical Society
4th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 59, Number 10
Tuesday–Saturday, October 7–11, 2014; Waikoloa, Hawaii
Session DK: Instrumentation II: Detectors for Low-energy Experiments |
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Chair: Pieter Doornenbal, RIKEN Room: Queen's 6 |
Thursday, October 9, 2014 9:00AM - 9:15AM |
DK.00001: Mitigation of Charge Sharing and Cross-Talk in a Planar Germanium Double-Sided Strip Detector N. Larson, S.N. Liddick, B.P. Crider, F.G. Kondev, S. Kumar, S.V. Paulauskas, C.J. Prokop, S. Suchyta Fragmentation facilities provide access to a wide range of beta-decaying nuclei for experimental study. However, the higher the atomic number of species of interest the greater the chance that the ion will not be fully stripped of its atomic electrons. The delivery of multiple charge states, predominately fully stripped and H-like, to the experimental system typically leads to overlaps in standard DE-TOF identification plots. A standard method for resolving multiple charge states is a measurement of the ion's total kinetic energy. A recently commissioned planar Ge double-sided strip detector (GeDSSD) is being used at the NSCL for beta-decay spectroscopy studies. The capability of the GeDSSD to measure total kinetic energies and resolve charge state contamination in a cocktail of radioactive ions is being investigated which requires addressing the dual problems of charge sharing between neighboring strips within the detector and electronic cross talk. Preliminary results will be presented. [Preview Abstract] |
Thursday, October 9, 2014 9:15AM - 9:30AM |
DK.00002: The polarization sensitivity of GRETINA Andreas Wiens The new tracking array GRETINA provides position information of the individual interactions of $\gamma$ rays within the active Ge detector material. The position knowledge of the first two interaction points enables the calculation of the Compton scattering angle, which is sensitive to the linear polarization. Measuring the angular distribution and the linear polarization can help determine the electromagnetic character of a transition and its parity. Inelastic proton scattering on Mg ($^{24}Mg(p,p'\gamma)$) provides highly polarized $\gamma$ rays which we used to characterize the polarization sensitivity of GRETINA. We have studied the angular distribution and the azimuthal Compton scattering angle of the 1368 keV gamma transition after signal-decomposition and tracking, which were normalized with the unpolarized results derived from $^{60}Co$. The $a_2$ and $a_4$ coefficients from the Legendre Polynomial fit of the angular distribution confirmed the high degree of polarization. We will report on the asymmetry in the azimuthal Compton scattering angle distribution which is in good agreement with a $\cos (2\varphi)$ fit. We will discuss the energy dependance of the polarization sensitivity and compare the results with a GEANT4 simulation. [Preview Abstract] |
Thursday, October 9, 2014 9:30AM - 9:45AM |
DK.00003: Study of the radiation damage on Ge detectors and background for CAGRAF Natsumi Ichige, Nori Aoi, Yassid Ayyad, Eiji Ideguchi, Chihiro Iwamoto, Takeshi Koike, Hirotaka Suzuki, Tomokazu Suzuki, Atsushi Tamii, Mana Tanaka, Tetsuya Yamamoto, Yasutaka Yamamoto CAGRA, jointly developed between the U.S. and Japan, is an array of 16 Clover-type Ge detectors with anti-Compton BGO shields. RCNP is one of the main hosts to CAGRA. A project called CAGRAF is started at RCNP where the high resolution reaction spectrometer Grand Raiden is considered to be coupled with CAGRA. A critical issue for this setup is a severity of radiation damages mainly caused by fast neutrons which would be produced in primary beams of a few-hundred-MeV proton. To investigate the degree of the neutron damages and background in the Ge energy spectrum, a test experiment was conducted at the Grand Raiden beam line at RCNP in May, 2014. Two sets of plastic and liquid scintillator counters are placed near a $^{12}$C target (30 mg/cm$^{2}$) for measurements of neutron flux from the p + $^{12}$C reaction with the beam energy of 392 MeV. The beam intensity is varied between 1 nA - 10 nA. One transistor reset-type Ge detector is placed at 10 cm or 50 cm away from the target center. The Ge energy spectra are taken with the CAGRA digital electronics. In this contribution, results of the test experiment will be presented. [Preview Abstract] |
Thursday, October 9, 2014 9:45AM - 10:00AM |
DK.00004: Performance of CHICO2 with GRETINA C.Y. Wu, D. Cline, A. Hayes, I.Y. Lee CHICO2 is an upgraded CHICO with the improved position resolution matching that of GRETINA. CHICO is a 4$\pi $ position-sensitive parallel-plate avalanche counter. This improvement is achieved by adding the $\varphi $ to the existing $\theta $ pixelation for the position sensing cathode board. The position determination is not from the pixel directly but from the delay-line readout technique. Additional improvements include the development of a new generation amplifier and a VME based data acquisition system. CHICO2 has been successfully integrated into (Digital)Gammasphere and GRETINA in ANL for the $\gamma $-ray spectroscopy study. The position resolution of 0.7$^{\circ}$ (1$\sigma )$ in $\theta $ and 1.7$^{\circ}$ in $\varphi $ is reached for CHICO2. The $\gamma $-ray energy resolution of 0.8{\%} is obtained using GRETINA/CHICO2. Three Coulomb excitation experiments were fielded so far; two are the stable beam experiments for studying the shape coexistence in $^{72}$Ge and $^{76}$Ge with a $^{208}$Pb target of 0.5 mg/cm$^{2}$ thickness. The third one is to measure the E3 strength in $^{144}$Ba (T$_{1/2} = $ 11.5 s), which is the CARIBU beam developed recently at ANL. The description of both hardware and software improvements together with the experimental results will be presented. This work is supported by DOE, DE-AC52-07NA27344 (LLNL) and DE-AC02-05CH11231 (LBNL) as well as the NSF for U. of Rochester. [Preview Abstract] |
Thursday, October 9, 2014 10:00AM - 10:15AM |
DK.00005: ABSTRACT WITHDRAWN |
Thursday, October 9, 2014 10:15AM - 10:30AM |
DK.00006: DESCANT - The DEuterated SCintillator Array for Neutron Tagging Vinzenz Bildstein, P.E. Garrett, D. Bandyopadhay, J. Bangay, L. Bianco, G. Demand, B. Hadinia, K.G. Leach, C. Sumithrarachchi, J. Wong, S.F. Ashley, B.P. Crider, M.T. McEllistrem, E.E. Peters, F.M. Prados-Est\'{e}vez, S.W. Yates, J.R. Vanhoy, G.C. Ball, A.B. Garnsworthy, G. Hackman, C.J. Pearson, F. Sarazin The DESCANT array at TRIUMF is designed to track neutrons from RIB experiments. DESCANT is composed of 70 close-packed deuterated organic liquid scintillators coupled to digital fast read-out ADC modules. This configuration will permit online pulse-shape discrimination between neutron and $\gamma$-ray events. The anisotropy of the $n-d$ scattering will allow distinction of higher neutron multiplicities from scattering within the array and determination of the neutron energy spectrum directly from the pulse-height spectrum without using TOF. A prototype detector has been tested with monoenergetic neutrons at the accelerator laboratory of the University of Kentucky and a $^{24}$Mg($^3$He, n)$^{26}$Si experiment has been performed with eight DESCANT detectors and two HPGe detectors. The results of the tests and the status of DESCANT will be presented. [Preview Abstract] |
Thursday, October 9, 2014 10:30AM - 10:45AM |
DK.00007: Bayesian Neural Networks for Ray Reconstruction of Spectrographs M.P. Kuchera, D. Bazin, B.M. Sherrill Spectrograph ray reconstruction is an important consideration for data analysis of many modern spectrometer experiments. Typically, calculated inverse ion-optical maps are used to reconstruct ion trajectories through a magnetic system. A standard practice is to calculate ion-optical maps using programs such as COSY Infinity and then use a procedure to invert these maps. The inverse maps are used to reconstruct ion parameters at the object location from measurements at the spectrograph focal plane. This presentation will present our exploration of an alternate method, namely, the use of Bayesian Neural Networks, BNN, for the construction of transport maps using experimental data. In order to study the effectiveness of the training of the neural network, COSY Infinity maps were used to generate training data for the S800 spectrograph at the National Superconducting Cyclotron Laboratory. BNNs were trained from this generated data, where the exact map is known, and a study of the method will be presented. Among the factors that will be reported are an accuracy of the BNN mapping, a study of the amount of training data necessary to construct an accurate BNN, and what level of precision in the training data is necessary for an accurate mapping. [Preview Abstract] |
Thursday, October 9, 2014 10:45AM - 11:00AM |
DK.00008: Rigidity Calibration of the A1900 Fragment Separator T.N. Ginter, F. Farinon, T. Baumann, M. Hausmann, E. Kwan, M. Portillo, J. Stetson, C.S. Sumithrarachchi, S.J. Williams With increased use of beams stopped in gas from the A1900 fragment separator, an improved rigidity calibration is more crucial than ever to establish accurate control for stopping ions in materials. The variation with rigidity of the bending radius of a dipole introduces error into the rigidity calibration of a device containing the dipole if this variation is not taken into account when scaling the device. In the case of the A1900, assuming a constant bending radius for the dipoles means that the rigidity calibration can be off by as much as 1\%. It is not trivial, however, to extract the relationship between the dipole bending radius and rigidity -- knowledge of which is required to compensate for the calibration discrepancy. A scheme to determine the relationship between radius and rigidity for all four A1900 dipoles has been developed employing a measurement of the beam rigidity based on time-of-flight. This scheme is presented along with initial results demonstrating the improvement to the A1900 rigidity calibration that can be achieved. [Preview Abstract] |
Thursday, October 9, 2014 11:00AM - 11:15AM |
DK.00009: Single-crystal diamond detectors for swift heavy ion beams Andreas Stolz, Ayan Bhattacharya, Timothy A. Grotjohn, John Yurkon The outstanding properties of diamond allow the development of particle detectors with very fast detector response and excellent radiation hardness. Detectors based on diamonds produced by chemical vapor deposition have been developed at Michigan State University. The performance of these detectors were studied at the National Superconducting Cyclotron Laboratory. First results of the investigation of the radiation tolerance of diamond detectors under the irradiation of swift heavy ions in the energy range of 100-150 MeV/u will be presented. [Preview Abstract] |
Thursday, October 9, 2014 11:15AM - 11:30AM |
DK.00010: Performance evaluation of multi sampling ionization chamber for heavy ion beams by comparison with GEANT4 simulation Yuki Kanke In high-energy heavy-ion accelerator facilities, multi sampling ionization chambers are often used for the identification of the atomic number $Z$ by detecting the energy deposit in it [1,2]. In the study at GSI, the picture of the escape of secondary electrons, $\delta$ rays, from the ionization chamber explains the experimental data of pulse-height resolution [3]. If this picture is correct, the pulse-height resolution should depend on the effective area of the ionization chamber. The experiment have been performed at NIRS-HIMAC. The pulse-height resolutions of two ionization chambers with different effective area were compared by using a 400-MeV/u Ni beam and their fragments. The difference in the pulse-height resolutions was observed. By comparison with the GEANT4 simulation including the $\delta $-rays emission, the performance of the ionization chamber have been evaluated. \\[4pt] [1] K. Kimura et al., Nucl. Instr. and Meth. A, 538, 608 (2005).\\[0pt] [2] Y. Sato et al., Jpn. J. Appl. Phys., 53, 016401 (2014).\\[0pt] [3] M. Pfutzuner, et al., Nucl. Instr. and Meth. B, 86, 213 (1994). [Preview Abstract] |
Thursday, October 9, 2014 11:30AM - 11:45AM |
DK.00011: RICH counter for heavy-ion particle identification using multi-anode photomultipliers Shintaro Yamaoka, Mitsunori Fukuda, Yusuke Morita, Ryosuke Kanbe, Kensaku Matsuta, Mototsugu Mihara, Junichi Ohno, Yasuto Kamisho, Masaomi Tanaka, Daiki Nishimura, Kenta Yoshinaga, Takashi Ohtsubo, Maya Takechi, Masayuki Nagashima, Takuji Izumikawa, Atsushi Kitagawa, Shigekazu Fukuda, Shinji Sato, Shinji Suzuki, Takeshi Suzuki, Takayuki Yamaguchi In order to develop a new RICH counter (Ring Imaging CHerenkov counter) for heavy-ion particle identification, we have constructed a test system for measurement of a ring image of Cherenkov light using multi-anode photomultipliers that detect a photon incident position. For a test, a $^{\mathrm{58}}$Ni(480MeV/u) beam provided by the HIMAC heavy-ion synchrotron was used. As radiators, we have tested synthetic silica, polycarbonate, and BK7. We have selected a wavelength of Cherenkov light by using a band pass filter. As a result, the ring image of Cherenkov light was observed and the obtained resolution of velocity will be reported at the meeting. [Preview Abstract] |
Thursday, October 9, 2014 11:45AM - 12:00PM |
DK.00012: Development of the new gamma-ray calorimeter for the measurement of Pigmy Dipole Resonance Mizuki Shikata, Takashi Nakamura, Yasuhiro Togano, Yosuke Kondo A new $\gamma$-ray calorimeter CATANA (\textbf{CA}lorimeter for gamma $\gamma$-ray \textbf{T}ransition in \textbf{A}tomic \textbf{N}uclei at high isospin \textbf{A}synmetry) has been developed to measure highly excited states like the pygmy dipole resonance and the giant dipole resonance. CATANA will be used with the SAMURAI spectrometer at RIBF. The excitation energy spectrum will be reconstructed combining the invariant mass of the reaction products measured by SAMURAI and $\gamma$-ray energies from CATANA. CATANA has focused on achieving a high detection efficiency. It is calculated as 56\% for 1 MeV $\gamma$-rays from beam with a velocity of $\beta$ = 0.6. The CATANA array consists of 200 CsI(Na) crystals and covers angles from 10 to 120 degrees along the beam axis. In this study, we have tested prototype crystals of CATANA to evaluate their performance. A position dependence of the light input have been measured and compared with a Monte-Carlo simulation based on GEANT4. In this talk, we will report the design of CATANA and the result of the tests and the simulation. [Preview Abstract] |
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