Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session B12: New Developments in Instrumentation |
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Sponsoring Units: DNP Chair: E. Norbeck, University of Iowa Room: Marriott Tampa Waterside Room 11 |
Saturday, April 16, 2005 10:45AM - 10:57AM |
B12.00001: A Deuteron Polarimeter for an EDM Search E.J. Stephenson, G. Noid, C.J.G. Onderwater The proposed search for an electric dipole moment (EDM) on the deuteron using the large induced electric field (in the deuteron rest frame) of a magnetic storage ring requires an efficient method for continuously monitoring the deuteron polarization. We propose to slowly extract the stored beam ($p=0.7$~GeV/c) using Coulomb scattering from a thin gas target. Scattered deuterons would then enter the polarimeter and scatter from a thick annular carbon target backed by an array of charged-particle detectors. The time dependence of the left-right asymmetry would contain the signal of an EDM. To obtain cross section and analyzing power measurements needed for the polarimeter design, we took data on deuteron-induced reactions and scattering at 80 and 110~MeV using the vector polarized beam at the KVI. Charged-particle telescopes gave energy information on all $Z=1$ reaction products. Large analyzing powers associated with rainbow scattering were observed. [Preview Abstract] |
Saturday, April 16, 2005 10:57AM - 11:09AM |
B12.00002: Investigation of Electron-beam Production of Neutron-Rich Radioactive Ion Beams J.J. Das, J.R. Beene, W.T. Diamond, J.D. Fox, J.W. Johnson, D.W. Stracener, M.J. Saltmarsh Photo-fission has been proposed for production of neutron-rich radioactive isotopes because potentially attractive absolute fission yields may be achieved with a modest-cost electron accelerator, and because the relative production of the most neutron-rich isotopes should be substantially enhanced in photo-fission compared to fission induced by protons and other light-ion beams. We intend to carry out measurements of isotopic yields in bremsstrahlung induced photo-fission of $^{238}$U at the Oak Ridge Electron Linear Accelerator (ORELA) at ORNL as part of an evaluation of this production method. A target for high-power electron beam irradiation at has been fabricated and tested. Fission products will be stopped in a closed-circuit, NaCl-loaded helium gas system and transported to a gamma ray detection system in order to measure the production of specific fission products. Measurements using a $^{252}$Cf source have confirmed that the transport efficiency is about 40{\%} through a 30 meter, 0.75 mm diameter stainless steel tube. The target assembly is to be mounted in the ORELA target room operated with up to 10 kW of $\sim $150 MeV electrons. [Preview Abstract] |
Saturday, April 16, 2005 11:09AM - 11:21AM |
B12.00003: Extending Physics Capabilities of the PHENIX Detector with Calorimetry at Forward Rapidities Vasily Dzhordzhadze The PHENIX detector at RHIC has been designed to study a different signatures of the states of matter created in heavy-ion collisions, and to investigate the spin structure of the nucleon. The PHENIX detector measures muons in two muon spectrometers, located at forward rapidities (1.2$<$eta$<$2.4) and hadrons, electrons, and photons in the two central spectrometers at mid-rapidity ($\vert $eta$\vert <$0.35). To make a next step in the PHENIX research program, it is necessary to extend the rapidity coverage beyond the limits set by the existing central spectrometer. The functionality of the PHENIX muon detectors can be extended with added capabilities to measure photonic and hadronic jets. Tungsten calorimeters with silicon pixel readout and fine transverse and longitudinal segmentation are proposed to attain this goal. The proposed calorimeters will be located in the forward directions on either side of the PHENIX interaction point. In this talk we report on the studies of functionality of the proposed calorimeters: the detector energy resolution, the jet reconstruction capabilities and the characteristics of the pion rejection. [Preview Abstract] |
Saturday, April 16, 2005 11:21AM - 11:33AM |
B12.00004: Development of Polarized Solid Targets for Spectroscopic Studies with Radioactive Ion Beams. J.P. Urrego-Blanco, C.R. Bingham, A. Galindo-Uribarri, B. van den Brandt, P. Hautle, J.A. Konter Exciting new findings with radioactive ion beams (RIBs) in nuclear spectroscopy have resulted in a growing interest in this field. In order to fully exploit the potential of RIBs it is necessary to develop appropriate experimental tools. We are investigating the possibility of introducing polarization observables in spectroscopic studies with RIBs, at energies around the Coulomb barrier, through polystyrene targets of polarized protons and deuterons in the thickness range between 20 and 100$\mu $m. The operation of such target systems requires a cooling scheme where the target is situated in the isolation vacuum of a cryostat in open connection to the vacuum of the beamline. This can be achieved by using two parallel polarized foils mounted on a copper tube, serving also as the NMR coil (for sampling the polarization), to form together a closed volume. Cooling of the foils is then achieved by a liquid helium bath ($^{4}$He or $^{3}$He) via the copper tube, and subsequently via a superfluid $^{4}$He film that can be added through the hollow NMR coil. The first tests of this proposed geometry are discussed and a status of the project is delivered. [Preview Abstract] |
Saturday, April 16, 2005 11:33AM - 11:45AM |
B12.00005: Sub-segment interaction-point determination for 32-fold segmented high-purity Germanium detectors D.-C. Dinca, C.M. Campbell, T. Glasmacher Sub-segment position resolution of the gamma-ray interaction points has been demonstrated for the cylindrically-symmetric 32-fold segmented HPGe detectors of the NSCL/MSU Segmented Germanium detector Array (SeGA) using digital electronics. Waveforms of the real charge signals from segments that contain interaction points and induced charge signals from neighboring segments were digitally recorded in 100 MHz ADCs. Integrated quantities are extracted from the waveforms. By analyzing the asymmetry of the induced signals we could determine the proximity of the interaction point to segments without net-charge deposition, attaining sub-segment position resolution along the crystals symmetry axis and for the azimuthal angle. The radial position of the interaction point was determined through an analysis of the rise times of the real charge signals. Although less precise than other methods involving complete waveform analysis, the use of integrated quantities makes the problem of sub-segment interaction position estimation simpler. [Preview Abstract] |
Saturday, April 16, 2005 11:45AM - 11:57AM |
B12.00006: Precision Mass Measurements with LEBIT at MSU G. Bollen, D. Davies, A. Doemer, J. Huikari, D.J. Morrissey, A. Prinke, R. Ringle, P. Schury, S. Schwarz, T. Sun, L. Weissman The Low-Energy beam and Ion Trap facility LEBIT opens the door to a new class of experiments with projectile fragment beams. The Coupled Cyclotron Facility at the NSCL delivers a large range of rare isotopes with high intensities, produced by the in-flight separation method. LEBIT converts these beams into low-energy beams using gas stopping and advanced ion guiding, cooling, and bunching techniques. The gas stopping cell has shown to efficiently stop relativistic ions and convert them into a low-energy continuous beam. The RFQ ion trap cooler-buncher shows excellent performance in converting such beams into brilliant pulses. First test mass measurements on stable isotopes performed with the 9.4 T Penning trap system show a very good accuracy. The status of LEBIT and the results of first measurments will be presented. [Preview Abstract] |
Saturday, April 16, 2005 11:57AM - 12:09PM |
B12.00007: Octupole Excitation of Trapped Ion Motion for Precision Mass Measurements G. Bollen, R. Ringle, P. Schury, S. Schwarz, T. Sun National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI, USA An azimuthal octupole radiofrequency field has been used to excite the ion motion of $^{40}$Ar$^{+}$ ions stored in a Penning trap. A resonant response was observed at twice the ions' true cyclotron frequency $\omega _{c}$=q/m$\cdot $B. The experiment has been performed with the 9.4-T Penning trap system of the recently commissioned LEBIT facility at the NSCL at MSU [1]. Similar to the excitation with an azimuthal quadrupole field at $\omega _{c}$ [2,3], octupole excitation at 2$\omega _{c}$ gives rise to a periodic beating of the ion motion between magnetron and reduced cyclotron motion. Differences are observed in the dependence of the excited ion motion on initial amplitudes and phases of the radial eigen motions. The observed behavior of the ions is found to be in good agreement with the results of numerical simulations. The technique still requires further testing but the first results indicate that 2$\omega _{c}$ excitation may provide benefits that are similar to doubling the magnetic field strength B. In particular precision mass measurements of short-lived rare isotopes may benefit from this technique by being able to reach a given precision with shorter ion storage and observation times. [1] S. Schwarz et al, Nucl. Instr. Meth. B204 (2004) 507 [2] G. Bollen et al., J. Appl. Phys. 68 (1990) 4355 [3] M. K\"{o}nig et al., Int. J. Mass Spec. Ion. Proc. 142 (1995) 95 [Preview Abstract] |
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B12.00008: A One-Dimensional RICH Detector with Wavelength Shifter Readout -- Principle and Monte Carlo Simulations Naipy Perez, Brian Beckford, Joerg Reinhold Ring imaging \v Cerenkov detectors (RICH) measure a particle's velocity by projecting the \v Cerenkov light cone on a plane and determining the radius of the resulting ring. Traditional detectors either employ a large number of photomultipliers (PMTs) or gaseous detectors with a highly segmented photosensitive cathode. Both principles require the readout of a large number of channels. For selected applications it may be sufficient, however, to measure a one-dimensional projection of the ring. This could be achieved with a plane of wavelength shifting bars that are read out by PMTs on both sides. This would result in a significantly reduced number of channels and therefore also more affordable designs. The photon collection efficiency of a wavelength shifting plate has been determined in a beam test performed at the PS facility at KEK. The talk will present the principle idea, Monte Carlo simulations of the performance of such a system based on the results from the beam test. [Preview Abstract] |
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