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 DJ: Instrumentation II |
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Sponsoring Units: DNP JPS Chair: Kim Lister, Argonne National Laboratory Room: Ritz-Carlton Hotel Hawaii |
Tuesday, September 20, 2005 7:00PM - 7:15PM |
DJ.00001: New Actinide Targets for Rare Isotope Beam Generation Andreas Kronenberg, H.K. Carter, E.H. Spejewski, D.W. Stracener, B. Chan, P. Dorhout Development of high-quality ion beams of short-lived isotopes is crucial for modern nuclear structure and nuclear astrophysics. The talk will focus on the development of targets for the production and release of neutron-rich isotopes, which are produced via fission of actinides. So far, only uranium carbide is widely used as a target, which has been produced and tested in various geometries with densities between 0.6 g/cm$^{3}$ and 6.0 g/cm$^{3}$. New compounds, such as thorium oxide, uranium boride (UB$_{2}$, UB$_{4}$ and UB$_{12})$ will be discussed and recent results presented. Thorium has a higher fission yield for certain isotopes in the mass region A=80 to 90 and the borides are of interest for a better understanding of the release process after the nuclear reaction. A comparison can be made between the release efficiency of UB$_{2}$, which has an alloy-type structure, and UB$_{12}$, which is of rock-salt type. The results from such high-temperature actinide compounds may be of interest for research on space reactor (nuclear thermal propulsion) design, as well as spent fuel storage. This research was sponsored by the NNSA under Stewardship Science Academic Alliance program through DOE Cooperative Agreement {\#} DE-FC03-3NA00143. [Preview Abstract] |
Tuesday, September 20, 2005 7:15PM - 7:30PM |
DJ.00002: Secondary Beam Lines in the Hadron Hall at J-PARC Hiroyuki Noumi, Keizo Agari, Erina Hirose, Masaharu Ieiri, Jun Imazato, Yohji Katoh, Michifumi Minakawa, Yoshinori Sato, Shinya Sawada, Yoshihiro Suzuki, Hitoshi Takahashi, Toshiyuki Takahashi, Minoru Takasaki, Kazuhiro Tanaka, Akihisa Toyoda, Yoshikazu Yamada, Yutaka Yamanoi, Hiroaki Watanabe A beam-line facility for nuclear and particle physics experiments, Hadron Hall, is being constructed at J-PARC in Tokai, Japan. A high-power proton beam of 750 kW from the 50-GeV Proton Synchrotron will be extracted to the Hadron Hall. High-intensity secondary kaons, pions, anti-protons, etc will be produced by irradiating a target with the primary proton beam. Huge amount of power deposit at the target will arise very high radiation and heated environment. Thus, beam-line equipments around the target must be resistant against high radiation dose and heat deposit. Since only a target, T1, will be placed in the Hadron Hall at the beginning, some secondary beam lines are designed to share T1 in order that various experiments can be carried out efficiently. Unique layout and performances of the secondary beam lines and relevant R{\&}D works will be presented. [Preview Abstract] |
Tuesday, September 20, 2005 7:30PM - 7:45PM |
DJ.00003: Precision Photon Flux Determination for the Jefferson Lab PrimEx Experiment Aram Teymurazyan The Hall B Jefferson Lab PrimEx Collaboration is using tagged photons to perform a 1.5\% level measurement of the absolute cross section for the photoproduction of neutral pions in the Coulomb field of a nucleus. Such a high precision pushes the limits of the photon tagging technique in regards to the determination of the absolute photon flux. The Collaboration has taken a multifaceted approach to this problem which has included measuring the absolute tagging ratios with a total absorption counter as well as relative tagging ratios with a pair spectrometer. In addition the PrimEx experimental setup, with its new state of the art hybrid calorimeter (HyCal), provides a unique opportunity to cross check the flux normalization procedure by measuring cross sections for well known electromagnetic processes. Data were collected during the Fall 2004 PrimEx run, and analysis is currently underway. Results of these investigations will be presented. [Preview Abstract] |
Tuesday, September 20, 2005 7:45PM - 8:00PM |
DJ.00004: Acceleration of polarized proton in the AGS with multiple partial Siberian snakes Junpei Takano, Leif Ahrens, Mei Bai, Kevin Brown, Ernest Courant, Christopher Gardner, Joseph Glenn, Toshiyuki Hattori, Haixin Huang, Fanglei Lin, Alfredo Luccio, William MacKay, Masahiro Okamura, Vadim Ptitsyn, Thomas Roser, Steven Tepikian, Nicholaos Tsoupas The polarized proton has been accelerated in Alternating Gradient Synchrotron (AGS) and Relative Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) for studying the spin physics of proton. The normal conducting helical dipole partial Siberian snake (Warm Snake) and the super conducting helical dipole partial Siberian snake (Cold Snake) have been installed in the AGS for overcoming the imperfection and intrinsic depolarizing resonances. The cold snake had been under commissioning in RUN5, but the polarization of the polarized proton in the AGS was improved with the warm snake only. The AGS also has a previously used solenoid partial snake. We will show a new idea of using three snakes for perfectly canceling the spin mismatch and some calculated results of spin tune with these three snakes. [Preview Abstract] |
Tuesday, September 20, 2005 8:00PM - 8:15PM |
DJ.00005: Preparation of Self-supporting targets of 11B and 13C Yoshiko Sasamoto, Takahiro Kawabata, Isao Sugai, Yasuhiro Takeda Alpha inelastic scattering measurements are planned in order to examine cluster structures in $^{11}$B and $^{13}$C. For precise measurements, self-supporting and high-quality targets with a thickness of $\sim$500 $\mu$g/cm$^{2}$ must be prepared. The vapor deposition is widely used to make thin carbon and boron films, but it is difficult to prepare self-supporting films thick enough by this method. Pressing method is also effective for preparation of high- purity films, but the films prepared by this method are thicker than 10 mg/cm$^{2}$. In the present work, a $^{11}$B target was prepared by the sputtering method with the electron-beam-excited plasma(EBEP). Argon plasma was produced by irradiating argon gas with the electron beam, and the argon ions extracted from the EBEP sputtered an isotopically enriched boron tablet. Finally, the sputtered boron particles were deposited on a substrate. A $^{13}$C target was prepared by the thermal cracking method. Cracking was performed by heating a Ta strip in a chamber filled with $^{13}$CH$_{4}$ gas. Then, the cracked carbon layer was formed on the Ta strip. The thickness, uniformity and purity of the prepared targets were investigated. [Preview Abstract] |
Tuesday, September 20, 2005 8:15PM - 8:30PM |
DJ.00006: Polarized proton solid target for $\vec{p}+^6$He elastic scattering experiment Satoshi Sakaguchi, Takashi Wakui, Tomohiro Uesaka, Hideyuki Sakai Recently, structures of unstable nuclei have been actively studied with radioactive nuclear beams. However measurement of spin polarization observables has not been possible in the research of unstable nuclei, because of the lack of polarized probe which is applicable for RI beam experiments. Due to the situations above, we have constructed a spin polarized proton solid target specialized for RI beam experiments. The target makes use of spontaneous electron alignment in photo-excited aromatic molecule, while ordinary polarized targets are based on Boltzmann polarization in high magnetic field. Reducing the magnetic field needed for polarization, our technique makes it possible to detect low energy recoiled protons in the scattering experiments under inverse kinematics condition. In this talk, recent progress and present situation of the target are reported. A radioactive beam experiment using this target is planned on July, 2005. In this experiment, we measure the vector analyzing power of the elastic scattering of $^6$He and polarized proton. Results obtained in this experiment will be reported as well. [Preview Abstract] |
Tuesday, September 20, 2005 8:30PM - 8:45PM |
DJ.00007: Study of an electron beam deflection with channeling in silicon crystals Shinya Sawada, Ichita Endo, Masataka Iinuma, Hirotoshi Kuroiwa, Takehiro Ohnishi, Sergey Strokov, Tohru Takahashi, Keitarou Ueda Crystal channeling is a promising way to deflect high energy particles. As the basis for future applications of crystal channeling for a beam-handling system, such as a beam-splitting system at J-PARC and a collimator at the International Linear Collider, electron-beam deflection with silicon crystals has been studied. A 150-MeV electron beam from the REFER electron ring at Hiroshima University was incident on a silicon crystal (16 $\mu$m). The profile of the beam after passing through the crystal was measured by an image intensifier at 2.34-m downstream of the crystal. If channeling occurs, the profile will change as the angle of the crystal changes. In this talk, results of the experiments are presented, as well as a comoparison with a simulation and future prospects. [Preview Abstract] |
Tuesday, September 20, 2005 8:45PM - 9:00PM |
DJ.00008: Higher-order calculations on a fragment separator layout for RIA M. Hausmann, A.M. Amthor, B.M. Sherrill, A. Zeller The planned Rare Isotope Accelerator (RIA) will provide unprecedented quantities of rare isotopes for basic science and potential applications. A key part of the RIA concept is a large acceptance fragment separator that is intended to efficiently collect and separate the exotic nuclides of interest. A preliminary baseline design of the pre-separator stage has been developed using the ion optical codes GRAPHIC TRANSPORT (by U. Rohrer based on a CERN-SLAC-FERMILAB version by K.~L. Brown {\it et al.}) and GICO (H. Wollnik {\it et al.}, AIP Conf. Proc. {\bf 177}(1988)74), where the latter is used also to optimize higher order corrections. In the present layout all relevant aberrations up to 3$^{rd}$ order are corrected at the pre-separator image plane and most of them also at the central intermediate image. Provisions are included for a beam dump system located slightly downstream of the first dipole magnet at an image location where the beam can be separated from the fragments of interest. Investigations of the preliminary layout with the Monte Carlo code MOCADI (N. Iwasa {\it et al.} NIM {\bf B126}(1997)284) indicate a transmission af about 60\% for $^{134}$Sn generated by induced fission of $^{238}$U. We will compare different ion optical solutions and present the status of our work. In the future we intend to further optimize the layout, to extend the calculations beyond 3$^{rd}$ order, and to verify the results using alternative codes, e.g. COSY INFINITY (K. Makino, M. Berz, NIM {\bf A427}(1999)338). [Preview Abstract] |
Tuesday, September 20, 2005 9:00PM - 9:15PM |
DJ.00009: Design and operation of a DANCE/LANSCE fission-tagging detector R.R.C. Clement, M. Fowler, J.A. Becker, T.A. Bredeweg, R.A. Macri, D.J. Vieira, C.Y. Wu, U. Agvaanluvsan, M. Chadwick, K. Moody, J. O'Donnell, W. Parker, R. Reifarth, R.S. Rundberg, J. Schwantes, J. Ullmann, J. Wilhelmy, P. Wilk, J.M. Wouters, J. Yurkon The 4$\pi $ BaF$_{2}$ Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos Neutron Science Center (LANSCE) was designed and built to measure neutron capture cross sections, X(n,$\gamma )$, for small, sub-milligram, radioactive samples. The DANCE beam-line at the Lujan Center provides neutrons from thermal to about one hundred keV permitting X(n,$\gamma )$ measurements over a large energy range. However, one difficultly in the neutron capture measurement on actinides is the contribution of the fission component X(n,f) to the measured gamma-ray spectrum. The solution to this dilemma is the addition of a fission-tag to the event. The fission-tagging detector is a cylindrical ppac (parallel plate avalanche counter) collocated with the fissionable sample. The response of the detector to fission fragment pairs would provide the necessary event information to separate the (n,$\gamma )$ and (n,f) reactions. A detailed description of the design and operation of the gas-handling system will be presented, together with details of the design and operation of the fission-tagging detector.$\backslash $Work performed under the auspices of the U.S. DoE by the University of California,Alamos National Laboratory (W-7405-ENG-36), Lawrence Livermore National Laboratory (W-7405-ENG-48) and the U.S. NSF by the National Superconducting Cyclotron Laboratory (PHY-0110253). Work benefited from use of Los Alamos Neutron Science Center (W-7405-ENG-36). [Preview Abstract] |
Tuesday, September 20, 2005 9:15PM - 9:30PM |
DJ.00010: Performance of the PbWO$_4$ Hybrid Electromagnetic Calorimeter at Jefferson Laboratory Marvin Payen The goal of the PrimEx experiment at Jefferson Lab is to perform a high precision measurement of the $\pi^0$ lifetime via the Primakoff effect. The initial data-taking phase has recently been completed. A new electromagnetic hybrid calorimeter (HYCAL) consisting of 1152 lead tungstate (PbWO$_4$) crystals and 576 lead (Pb) glass Cherenkov modules was constructed by the collaboration to conduct the lifetime measurement with a precision of 1.5\%. This novel electromagnetic calorimeter has high resolution, acceptance, and efficiency; characteristics that are required for the detection of the $\pi^0$ decay photons. The HYCAL has been tested with photon beams in the few GeV energy range. Results for the energy and position resolutions for both PbWO$_4$ and Pb-glass, including the transitions regions, will be presented.\\ \\ This project is supported under NSF MRI grant PHY-0079840. [Preview Abstract] |
Tuesday, September 20, 2005 9:30PM - 9:45PM |
DJ.00011: Liquid Hydrogen Target Cooled by Liquid Helium for Pentaqurak Experiment Shigeru Ishimoto, Kenichi Imai, Kimio Morimoto, Daisuke Nakajima, Shoji Suzuki, Nobuaki Tanaka A liquid hydrogen target for the pentaquark experiment (KEK-PS, E559) has been successfully developed at KEK 12 GeV PS (proton synchrotron). The target sizes are 67.8 mm diameter and 110 mm length. The hydrogen vessel was made from PET (Polyethylene Terephthalate) for the cylinder, and Mylar for end caps. The vessel thickness was 0.12$\sim $0.32 mm. The cylinder material PET t=0.3 mm was obtained from a commercial PET bottle for drinking water. The hydrogen target was cooled by a heat exchanger and continuous flow of cold helium gas from liquid helium container. The cooling time from room temperature to full of liquid hydrogen at 20 K was about 3 hrs. The consumption of liquid helium was 1.3$\sim $2.0 l/hr during stable operation. In the preparation stage, the hydrogen pressure was stabilized at 110.9 $\pm $ 0.07 kPa for more than 10 hrs. The measured target temperature was 21.06 $\pm $ 0.015 K., then the fluctuation of hydrogen density was obtained as $\pm $ 2.3 $\times $ 10 $^{-4}$. [Preview Abstract] |
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