Bulletin of the American Physical Society
2005 2nd Joint Meeting of the Nuclear Physics Divisions of the APS and The Physical Society of Japan
Sunday–Thursday, September 18–22, 2005; Maui, Hawaii
Session EJ: Instrumentation III |
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Sponsoring Units: DNP JPS Chair: Tomofumi Nagae, KEK IPNS Room: Ritz-Carlton Hotel Hawaii |
Wednesday, September 21, 2005 9:00AM - 9:15AM |
EJ.00001: The 8$\pi$ Spectrometer: A Detector Array for Decay Spectroscopy W.D. Kulp The 8$\pi$ spectrometer, an array of 20 Compton-suppressed HPGe detectors arranged in a regular icosahedral geometry, was originally designed for $\gamma$-ray coincidence spectroscopy following heavy-ion reactions. At TRIUMF/ISAC-I, the 8$\pi$ has been recommissioned for studies of rare radioactive decays. The symmetry of the array virtually eliminates the effects of $\gamma-\gamma$ angular correlations when the integrated array is used in coincidence spectroscopy. When $\gamma-\gamma$ coincidences are analyzed by the five possible angles between detector pairs, however, rich angular correlation information may be extracted. Results from angular correlation decay studies with the 8$\pi$ will be presented and implications for high-granualarity detector arrays will be discussed. [Preview Abstract] |
Wednesday, September 21, 2005 9:15AM - 9:30AM |
EJ.00002: Reduction of $\gamma$-ray background using Compton camera Y. Gono, A. Odahara, S. Motomura, Y. Isozumi, T. Kikegawa, Y. Motizuki, T. Fukuchi, Y. Wakabayashi Development of the method to reduce the background $\gamma$- rays was carried out by using the Compton camera. Compton camera can make the image of the distribution of the $\gamma$-ray source. A change of a decay constant of $^{40}$K under high pressure is studied with interests in the fields of nuclear physics, nuclear astrophysics and earth science. As much amount of $^{40}$K chemical compound is included in the earth, the $\gamma$-ray of 1461 keV is easily observed as a natural background. It is crucial to reduce the natural background $\gamma$-rays in this experiment. RIKEN group developed the Compton camera which is called to be GREI (Gamma-Ray Emission Imaging). GREI consists of two double sided strip Ge detectors. By selecting events that the only $\gamma$-rays are emitted from the source position, it was found that the background $\gamma$-rays could be reduced about 94 \%. This effect corresponds to that by a shield of the 4.7 cm thick lead bricks. [Preview Abstract] |
Wednesday, September 21, 2005 9:30AM - 9:45AM |
EJ.00003: Freons in Parallel Plate Avalanche Counters (PPACs) E. Norbeck, J.E. Olson, Y. Onel Freons that contain only C, H, and F are still allowed at National Laboratories because they do not harm the ozone layer. The perfluoroalkanes, no H or double bonds, have the additional advantage of being nontoxic and can be recirculated through a purifier cartridge that removes all impurities except noble gasses. At atmospheric pressure small molecules are preferred because they require less voltage. As a PPAC gas, CF$_{4 }$and R134A (CFH$_{2}$CF$_{3})$, the working fluid in automobile air conditioners, give similar results. With a plate spacing of 0.6 mm at 3050 V and 700 torr, R134A gave signals of amplitude 350 mV and width 1.5 ns with the detector directly coupled into 50 $\Omega $ cable. The radiation source was Compton scattered electrons from a 7 mCi $^{137}$Cs gamma-ray source. Methane, CH$_{4}$, gave similar results, but with much less primary ionization because of the small molecular weight. The mixture, 95{\%} Ar + 5{\%} CO$_{2}$, required only 1000 V, but the signals were smaller and slower. If low pressures are required, heavy gasses are preferred because of the larger amount of primary ionization. Perfluoropropane, C$_{3}$F$_{8}$, and perfluorocyclobutane, C$_{4}$F$_{8}$, are gasses at room temperature that work well in the 20 to 100 torr range with a 0.6 mm plate spacing, but are less useful with a 2.5 mm spacing. For all of the PPAC gasses, small amounts of impurities reduce the threshold voltage for sparking. [Preview Abstract] |
Wednesday, September 21, 2005 9:45AM - 10:00AM |
EJ.00004: Auto scanning system for the hybrid emulsion experiment. T. Watanabe, K. Nakazawa, T. Hibi, T. Kameyama, H. Nakamura, K. Imai, K. Miwa, H. Shibuya, S. Ogawa, J.S. Song, C.S. Yoon, S.H. Kim Hybrid emulsion experiment, KEK-E373, had been carried out to study baryon-baryon interaction in $S=-2$ sector via $\Xi^{-}$ capture in the emulsion which produced $(K^{-},K^{+})$ process. In the present, 3 hypernuclear events and 2 twin hypernulear events are found. Furthermore a candidate of $\Sigma^{-}$ emission events from $\Xi^{-}$ capture is also found These events give inportant information on $B-B$ interaction. In the future, new experiments (BNL-E964 and one at J-PARC) are planned in order to study $B-B$ interaction systematically. In the experiment, position of produced $\Xi^{-}$s in the emulsion was predicted from $(K^-,K^+)$ reaction kinematics by analyzing counter data. Therefore, searcing area of the emulsion could be limitted and effective analysis could be realized. However, in the future experiments number of produced $\Xi^-$ become 10 or more times than that of KEK-E373. And if the analyzing speed is enough to search all area of the emulsion, non-triggered $\Xi^{-}$s produced by $K^{-}n\rightarrow K^{0}\Xi^{-}$ can be detected. In order to analyze these data, new auto scanning system have been developped. In the system CCD camera which shot the emulsion image don't stop in the analysis. Thus, dead time caused by go-stop process in changing search area become to 0. [Preview Abstract] |
Wednesday, September 21, 2005 10:00AM - 10:15AM |
EJ.00005: Electron identification capability of real size Transion Radiation Detector for ALICE using neural network method Yuhei Morino, Shota Saito, Taku Gunji, Hideki Hamagaki, Kyochiro Ozawa It is predicted from QCD theory that the phase transition would be occured from ordinary hadronic matter to a plasma of de-confined quarks and gluons, called quark-gluon-plasma (QGP) at high energy density and high temperature. ALICE experiment is one of the experiments which will be held at Large Hadron Collider at CERN in near future (2007). The physics goal of the ALICE experiment is to study such QCD phase transition at CMS energy of $\sqrt{s_{NN}} $= 5.5 TeV. ALICE Transition Radiation Detector (TRD) will be installed to provide electron identification and particle tracking. For measurements of quarkonia, it is requared for the ALICE TRD to satisfy pion rejection factor of larger than 100 at 90\% electron efficiency. The TRD for ALICE is now in the production stage. A first beam test of full size six-chamber detector stack of TRD was performed at CERN PS beam line in October 2004. In this talk, electron identification capability using neural network method will be reported. [Preview Abstract] |
Wednesday, September 21, 2005 10:15AM - 10:30AM |
EJ.00006: Nuclear Emulsion Treatment for Study of $S=-2$ Nuclear Systems at AGS-E964 Tetsuya Hibi The purpose of the E964 experiment is to study $S=-2$ nuclear systems with 10$^4$ stopping events of $\Xi^-$ hyperons and also to know $\Xi^-$$N$ interaction by measuring atomic X-ray from $\Xi^-$ absorption, for the first time. In the experiment, nuclear emulsion is used for detecting sequential weak decay of double-$\Lambda$ hypernuclei and also pointing $\Xi^-$ hyperons stopping events in huge amount of X-ray data. We have developed a new type of nuclear emulsion for E964. Very thin film made of polyethyleneterephthalate (PET) is used for the first time as emulsion support so as to minimize a dead space. We use the emulsion with fine and uniform AgBr(I) crystal of the size of 0.18$\pm$0.015$\mu$m, which was improved from that used in the previous experiments (0.24$\pm$0.078$\mu$m) to get better position resolution. A method of its treatment is reported in detail on each process of plate making, beam exposure and development. [Preview Abstract] |
Wednesday, September 21, 2005 10:30AM - 10:45AM |
EJ.00007: Recent development of the Optical Transition Radiation detector at the J-PARC slow-extraction beam line Akihisa Toyoda, Keizo Agari, Erina Hirose, Masaharu Ieiri, Yohji Katoh, Michifumi Minakawa, Hiroyuki Noumi, Yoshinori Sato, Yoshihiro Suzuki, Hitoshi Takahashi, Minoru Takasaki, Kazuhiro Tanaka, Yoshikazu Yamada, Yutaka Yamanoi, Hiroaki Watanabe The J-PARC slow-extraction beam line under construction will provide a high intensity proton beam with a beam power of 750 kW. To handle such high intensity beam line safely, it is necessary to monitor the beam profile precisely without fault. Moreover, the beam loss at the beam monitor itself should be minimized to reduce the residual dose rate and the heat deposition at the beam monitor. As such beam profile monitor, we have developed the OTR (Optical Transition Radiation) detector. This monitor is composed of the OTR screen as a radiator and a camera system with an image intensifier to measure the OTR light. Because the OTR light intensity only depends on the reflectivity of the OTR screen, we can minimize a thickness of the OTR screen so that the problem of the residual dose and the heat deposition is expected to be resolved. In this talk, we will report the result of the beam test of a prototype OTR detector performed at KEK-PS beam line. The beam response, a background condition, and a readout system will be presented. [Preview Abstract] |
Wednesday, September 21, 2005 10:45AM - 11:00AM |
EJ.00008: Simultaneous measurement of (n,$\gamma$) and (n,fission) cross sections with the DANCE $4\pi$ BaF$_2$ array T.A. Bredeweg, M.M. Fowler, E.M. Bond, M.B. Chadwick, E.-I. Esch, L.F. Hunt, J.M. O'Donnell, R.S. Rundberg, J.M. Schwantes, J.L. Ullmann, D.J. Vieira, J.B. Wilhelmy, J.M. Wouters, T. Ethvignot, T. Granier, R.R.C. Clement, R.A. Macri, J.A. Becker, J.E. Yurkon Neutron capture cross section measurements on many of the actinides are complicated by low-energy neutron-induced fission, which competes with neutron capture to varying degrees depending on the nuclide of interest. Measurements of neutron capture on $^{235}$U using the Detector for Advanced Neutron Capture Experiments (DANCE) have shown that we can partially resolve capture from fission events based on total photon calorimetry. The addition of a fission-tagging detector to the DANCE array will greatly improve our ability to separate these two competing processes so that improved neutron capture and (n,$\gamma$)/(n,fission) cross section ratio measurements can be obtained. Such an addition to the DANCE array will also provide a means to study several important issues associated with neutron-induced fission, including (n,fission) cross sections as a function of incident neutron energy, and total energy and multiplicity of prompt fission photons. We have focused on two detector designs with complementary capabilities, a parallel-plate avalanche counter and an array of solar cells. Results from the initial in-beam tests of these two designs will be presented. [Preview Abstract] |
Wednesday, September 21, 2005 11:00AM - 11:15AM |
EJ.00009: A Comprehensive New Detector (R2D) at RHIC II John W. Harris Results from the Relativistic Heavy Ion Collider (RHIC) have established that a new state of matter has been formed in collisions of heavy ions at $\sqrt{s_{NN}}$ = 200 GeV. However, fundamental questions remain to be addressed regarding whether the system is deconfined, chiral symmetry is restored, a color glass condensate exists, and how the system evolves through eventual hadronization. Jets, heavy flavors and electromagnetic probes are sensitive to the initial high density stage, and should provide the requisite new insight. Such a thorough investigation necessitates jet measurements with particle identification at large momenta, measurement of all quarkonium states up to the Y(3s) state including feed-down in pp, pA and AA, and measurements at forward rapidities including forward-midrapidity correlations. For this purpose, we propose$^*$ a comprehensive new detector for upgraded luminosity RHIC II operation with large acceptance (-3 $<\eta <$ 3, $\Delta\phi = 2 \pi$) tracking and calorimetry in a 1.5 T solenoidal magnetic field for hadron, muon and photon identification and momentum measurements up to 20-30 GeV/c. We describe the detector, summarize its performance and discuss its potential physics impact in an era with heavy ions in the Large Hadron Collider.\\ $^*$ P. Steinberg et al., nucl-ex/0503002. [Preview Abstract] |
Wednesday, September 21, 2005 11:15AM - 11:30AM |
EJ.00010: Measurements of Stability of Gas Electron Multiplier (GEM) Yorito Yamaguchi, Hideki Hamagaki, Kyoichiro Ozawa, Susumu Oda, Masahide Inuzuka Recently, we produce a new type of Gas Electron Multiplier (GEM) foils by a plasma etching method. We investigate the gain stability of the GEM made at CNS, University of Tokyo. The GEM, which has been originally developed at CERN using micro-pattern technology, is expected to have the possibility of high rate operation together with good spatial resolution. The GEM made at CERN (CERN-GEM) is produced by the chemical etching method and has holes with a double-conical shape. It has been reported that the gas gain of CERN-GEM increases (or decreases) as a function of illumination time. One possible reason of the illumination-time dependence is that the Kapton insulator in the GEM charges up. The charging-up is thought to be due to a double-conical shape of holes of the CERN-GEM. We succeeded in producing the GEM (CNS-GEM) which has holes with a cylindrical shape by the plasma etching method. The CNS-GEM is expected to have better gain stability than CERN-GEM since the CNS-GEM has better electron transmission and less probability of charging-up. In this talk, the result of measurements for gain stability of the CNS-GEM compared with that of the CERN-GEM and the current status of development of the CNS-GEM will be reported. [Preview Abstract] |
Wednesday, September 21, 2005 11:30AM - 11:45AM |
EJ.00011: Development of Residual Gas Ionization Profile Monitor for slowly extracted proton beams Yoshinori Sato, Keizo Agari, Masaharu Ieiri, Yohji Katoh, Erina Hirose, Yoichi Igarashi, Susumu Inaba, Michifumi Minakawa, Hiroyuki Noumi, Masatoshi Saito, Yoshihiro Suzuki, Hitoshi Takahashi, Minoru Takasaki, Kazuhiro Tanaka, Akihisa Toyoda, Yoshikazu Yamada, Yutaka Yamanoi, Hiroaki Watanabe We have developed Residual Gas Ionization Profile Monitor (RGIPM) for slowly extracted proton beams at Japan Proton Accelerator Research Complex (J-PARC). Beam monitors must be non- destructive to keep beam losses as low as possible for maintenance reasons. The profiles of beams are measured by collecting knock-on electrons produced by ionization of residual gas in 1 Pa vacuum. Applying the magnetic field parallel to the collection electric field is essential to reduce diffusion by collisions of electrons with residual gas molecules. A prototype RGIPM has been installed in the slow-extraction beam line at KEK 12 GeV Proton Synchrotron. The results of the test experiments of the prototype monitor are presented. [Preview Abstract] |
Wednesday, September 21, 2005 11:45AM - 12:00PM |
EJ.00012: Progress in the Development of a Lead Slowing-Down Spectrometer at LANSCE R.C. Haight, S.A. Wender, J.M. O'Donnell, A. Michaudon, D.J. Vieira, J.M. Schwantes, T.A. Bredeweg, E.M. Bond, J.B. Wilhelmy, D. Rochman, T. Ethvignot, T. Granier, Y. Danon, C. Romano Lead Slowing-Down Spectrometers (LSDS) have been used for many years to measure neutron-induced fission cross sections of very small samples of actinides. We are extending the range to ultra-small samples by driving a 20-ton LSDS with short, intense pulses of 800-MeV protons from the Proton Storage Ring at the Los Alamos Neutron Science Center. Neutrons are produced by the pulsed proton beam from the LANSCE Proton Storage Ring striking a tungsten target in the center of the lead. Fission reactions are detected as a function of time, and therefore neutron energy, after the beam pulse. Initial experiments have confirmed the calculated performance of the LSDS and have demonstrated the capability of measuring the neutron-induced fission cross section of Pu-239 with a sample mass of less than 10 nanograms. Progress in the development of this new capability and plans for a program of measurements will be described. [Preview Abstract] |
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