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 DK: Instrumentation for Electro Weak Interactions |
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Sponsoring Units: DNP JPS Chair: Brian Fujikawa, Lawrence Berkeley National Laboratory Room: Ritz-Carlton Hotel Maui |
Tuesday, September 20, 2005 7:00PM - 7:15PM |
DK.00001: A Polarized $^3$He Neutron Spin Filter for $n+p\rightarrow d+\gamma$ Tim Chupp The $n + p \rightarrow d + \gamma$ experiment uses a pulsed cold neutron beam to measure $A_\gamma$, the parity-violating correlation of neutron spin and the direction of gamma--ray emission upon capture of polarized neutrons by protons. A large area polarized $^3$He neutron spin filter has been constructed and used for measurements on the FP12 beam line at the Los Alamos Neutron Scattering Center. The spin--filter consists of roughly cylindrical cells 5 cm thick with 10--12.5 cm inside diameter, which covers most of the available neutron beam area. The cells, made at NIST, use boron free, alumino--silicate glass (GE-180) and are filled with about 1 atmosphere (at room temp.) of $^3$He, natural rubidium and N$_2$. Two broadband, 30 W laser diode arrays coupled to optical fibers irradiate the cell and polarize rubidium vapor. Polarization is transferred to $^3$He nuclei though spin-exchange collisions. The transmission of neutrons through the spin filter is used to measure the neutron polarization, and the $^3$He polarization is extracted from the wavelength dependence. Continuous $^3$He polarization greater than 50\% ($\pm$ 2\%) has been maintained over the course of several weeks. A $^3$He analyzer cell, polarized off-line can be positioned down stream from the experiment to monitor neutron polarization and spin flipping. Cell construction, polarizer design, performance, and polarimetry will be described in this talk. [Preview Abstract] |
Tuesday, September 20, 2005 7:15PM - 7:30PM |
DK.00002: Dressed Helium Comagnetometry for the Neutron EDM Experiment A. Esler, J.C. Peng, S.K. Lamoreaux, C.Y. Liu, J. Torgerson The electric dipole moment (EDM) of the neutron provides a unique window into CP-violating processes in the light-quark baryon sector. A new experiment with ultracold neutrons aims to measure the neutron EDM with a sensitivity of $10^{-27}$~e-cm. The experiment will use a novel direct comagnetometry technique with polarized $^{3}$He ``dressed'' by a RF magnetic field, to match its effective magnetic moment to that of the neutron. This method allows a sensitive measurement of the neutron precession rate relative to the $^{3}$He. We have studied the dressed $^{3}$He spin system experimentally using a polarized $^{3}$He source at Los~Alamos. Results of this first measurement of spin dressing effects on the $^{3}$He magnetic moment will be presented. [Preview Abstract] |
Tuesday, September 20, 2005 7:30PM - 7:45PM |
DK.00003: A New Ultracold Neutron Source for Fundamental Physics Yasuhiro Masuda Ultracold neutrons (UCN) can be used for various kinds of experiments on fundamental physics, for example neutron EDM, neutron beta decay, gravity, neutron capture of RI beams and n-nbar oscillation. In these experiments, UCN density is the most important parameter. New generation UCN sources are being developed in many institutes in the world. We are developing a spallation UCN production in superfluid helium (He-II) [1]. In the mini-symposium, we will discuss the present status and future possibilities of the He-II spallation UCN source.\newline \newline [1] Y. Masuda et al. Phys. Rev. Lett. 89 (2002) 284801. [Preview Abstract] |
Tuesday, September 20, 2005 7:45PM - 8:00PM |
DK.00004: Analysis of Ultracold Neutron Depolarization Studies Y.-P. Xu, H.O. Back, A.T. Holley, R.W. Pattie, A.R. Young, J.-H. Yuan, P. Geltenbort, M. Makela, A. Saunders, A. Pichlmaier, R.R. Mammei, M. Pitt, R. Vogelaar Studies of ultracold neutron (UCN) transport and depolarization provide important support data for experiments such as the UCNA experiment at LANSCE. The UCNA experiment's goal is to make an absolute measurement of the beta-asymmetry for neutron decay using UCN, a measurement which requires essentially 100\% polarized UCN. We present progress on the analysis of several experiments conducted at ILL which have measured the depolarization rate for UCN on guides with diamond-like carbon (DLC) coatings. These experiments provide a consistent picture of depolarization rates expected for these coatings on non-magnetic substrates, and indicate that DLC coatings will be more than adequate for the UCNA project's first planned measurements. [Preview Abstract] |
Tuesday, September 20, 2005 8:00PM - 8:15PM |
DK.00005: Solid State Ultra-Cold Neutron Detectors Seth Hoedl, Adam Holley, Alejandro Garcia, Peter Geltenbort, Dan Melconian, Anne Sallaska, Sky Sjue, Albert Young The reflective properties of Ultra-Cold Neutrons (UCN) enable easy transport and bottling, but, make neutron detection a technical challenge. Typically, UCN are allowed to accelerate in the Earth's gravitational field to sufficient velocity to penetrate an aluminum entrance window of a $^3$He proportional counter. Here we describe the construction and characterization at the ILL of two kinds of prototype solid-state detectors which can be used to monitor the UCN density inside the UCNA spectrometer without gravitational acceleration, and perhaps more critically, without the danger of $^3$He leaks. The first type consists of 300~$\mu$g/cm$^2$ of LiF (natural isotopic abundance) evaporated on $\sim 1 \mu$m~thick nickel foils. The second type consists of $\sim 10^{18}$ $^{10}$B ions implanted in a 2000\AA\ thick vanadium layer, also evaporated onto nickel foils. We find that both types have a lower critical velocity than aluminum, and thus, outperform aluminum window proportional counters for \emph{in-situ} density measurements. [Preview Abstract] |
Tuesday, September 20, 2005 8:15PM - 8:30PM |
DK.00006: The UCN Source at LANSCE M. Makela, T. Bowles, R. Hill, G. Hogan, S. Lamoreaux, C. Morris, A. Saunders, T. Kawai, B. Filippone, B. Plaster, J. Yuan, P. Geltenbort, K. Soyama, A.R. Young, Y.-P Xu, A. Serebrov, T. Kitagaki, A. Garcia, S. Hoedel, A. Sallaska, S. Sjue, T.M. Ito, R.B. Vogelaar, R.R. Mammei, M. Pitt A new source of ultra-cold neutrons (UCN), using on a solid deuterium moderator has been built at the Los Alamos Neutron Science Center (LANSCE). Closely based on a prototype that was tested at Los Alamos, the new source supplies two UCN beam lines: one for the UCNA experiment and the other for development of the Los Alamos UCN EDM experiment and a neutron lifetime experiment. The LANSCE 800 MeV proton beam creates spallation neutrons from a tungsten target. The spallation neutrons are cooled with a cold polyethylene moderator. These cool neutrons then interact with solid deuterium and become UCN. This talk will present a summary of the current source design, it UCN production capabilities, and some aspects of UCN delivery to planned experiments [Preview Abstract] |
Tuesday, September 20, 2005 8:30PM - 8:45PM |
DK.00007: Performance Characteristics of A Low-Background Front-End Electronics Package for Germanium Spectrometers Todd Hossbach, Craig Aalseth The Majorana project is a next-generation {$^{76}$Ge} neutrinoless double-beta decay search, using 57 isotopically- enriched segmented germanium crystals mounted in each of 8 modular cryostats. This configuration provides physical granularity which should reject most expected backgrounds. To achieve greater effective granularity, a method of radial pulse-shape analysis is planned. Maximum PSD efficacy is achieved with low-noise electronics and a minimal signal bandwidth of $\sim$25~MHz. Pacific Northwest National Laboratory has developed a fourth generation Low-Background Front-End Electronics Package (LFEP-4) using carefully selected and screened low-background components. The performance characteristics of the LFEP-4, namely bandwidth, noise, and energy resolution, have been quantified and compared with conventional HPGE front-end electronics. To meet the requirements of the Majorana experiment, a fifth-generation LFEP has been designed with lower power dissipation and increased signal bandwidth, while maintaining a minimal footprint. Details of the LFEP-5 design and anticipated performance are presented. [Preview Abstract] |
Tuesday, September 20, 2005 8:45PM - 9:00PM |
DK.00008: Search for WIMPs Dark Matter by means of segmented NaI(Tl) scintillator Ken-Ichi Fushimi, Hideyuki Kawasuso, Masako Toi, Eriko Aihara, Rena Hayami, Kensuke Yasuda, Erika Matsumoto, Shintaro Nakayama, Norihiko Koori, Kayoko Ichihara, Saori Umehara, Ryuta Hazama, Sei Yoshida, Masaharu Nomachi Searching for WIMPs dark matter with highly segmented NaI(Tl) scintillator array is proposed. The sensitivity was estimated by means of Monte Carlo simulation and it was found that the detector array had high sensitivity for not only spin-dependent excitation (EX) but also spin-independent (SI) interaction. The performance of the prototype thin NaI(Tl) plate scintillator with the thickness of 0.05cm and wide area of 5cmX5cm will be presented in this meeting. It has shown the excellent energy resolution of 21{\%}(FWHM) at 60keV gamma ray and the low energy threshold of a few keV. [Preview Abstract] |
Tuesday, September 20, 2005 9:00PM - 9:15PM |
DK.00009: Pulse Shape Discrimination for HPGe Detectors in Search for Dark Matter Dongming Mei, Andrew Hime, Steve Elliott In the detection of WIMP-induced nuclear recoil with a high-purity germanium detector, the main background source is electron recoil produced by natural and cosmogenic radioactivity. The capability of discriminating a nuclear recoil from an electron recoil is crucial to reduce the background and to reach good sensitivity for the detection of WIMPs. Digital pulse shape analysis is an encouraging approach to the discrimination of nuclear recoils from electron recoils. The sensitivity of pulse shape is essentially governed by two effects: (1) the drift time of the charge carriers that move along the electric field lines towards the corresponding electrode; (2) the density of electron-hole pairs along the track of the particle. A high density of charge carriers along the ionization track forms a plasma-like cloud of charge that shields the interior from the influence of the electric field and eventually results in a longer drift time. Both effects govern the pulse rise time associated with charge collection. Nuclear recoils induced by neutrons in a segmented Ge detector lead to a study of pulse rise time differences between these two classes of events and we provide a preliminary result on the potential of this technique. [Preview Abstract] |
Tuesday, September 20, 2005 9:15PM - 9:30PM |
DK.00010: Polarized $^3$He ion source, SEPIS based on the spin-exchange collisions Masayoshi Tanaka, Yutaka Takahashi, Keiji Takahisa, Masaru Yosoi, Shigehiro Yasui, Yasuhumi Komeno, Chika Inaba, Tadashi Shimoda, Hideaki Izumi, Takeshi Furukawa Over the decade we have developed the polarized $^3$He ion source for spin physics research at intermediate energy regions. Though we started constructing an OPPIS polarized $^3 $He ion source at first, we failed in obtaining a highly polarized $^3$He beam contrary to the great success in the proton OPPIS. Next, we proposed and checked the validity of an ``electron pumping'' polarized $^3$He ion source, EPPIS. Though the EPPIS decisively demonstrated its usefulness, the further development is currently suspended because of practical difficulty associated with a budget. To overcome this we proposed a SEPIS polarized ion source based on the enhanced spin-exchange cross sections between alkali atoms and an incident $^3$He$^+$ ion at extremely low energies less than 1 keV, which is expected by the theoretical calculation allowing the quasi-molecule formation. An advantage of SEPIS relative to EPPIS is that no pumping laser with a high intensity, and a high magnetic field to keep the polarization are required. The construction of bench-test device for the SEPIS will soon be in completion. We hope to present not only the present status of the construction of SEPIS but also the first preliminary result on the SEPIS performace in this joint meeting. [Preview Abstract] |
Tuesday, September 20, 2005 9:30PM - 9:45PM |
DK.00011: Development of a Polarized $^{6}$Li$^{3+}$ Ion Source at RCNP A. Tamii, K. Hatanaka, K. Fujita, H. Matsubara, S. Morinobu, S. Ninomiya, Y. Sakemi, Y. Shimizu, Y. Tameshige, T. Uesaka, T. Wakui, H. Okamura, T. Wakasa, T. Nakagawa Nuclear spin-isospin excitations show rich features in various nuclei. One of key points to study such excitations is to use a selective probe for the reactions relevant to the physics of interest. Our plan is to develop a new polarized $^{6}$Li$^{3+}$ ion source for producing $^{6}$Li$^{3+}$ beams at 100 MeV/U at the Research Center for Nuclear Physics (RCNP). Polarized $^{6}$Li atoms are produced by the optical pumping method. The atoms are injected into an 18GHz ECR ionizer for producing 3+ ions, directory or after being stripped of an electron by using a surface ionizer. Several depolarization processes should be cared, such as the ones due to inhomogeneous magnetic field, ECR effect in the RF field, excitation and de-excitation processes of ions, etc. We will report on the design of the ion source and recent results of feasibility tests. [Preview Abstract] |
Tuesday, September 20, 2005 9:45PM - 10:00PM |
DK.00012: Development of a high efficiency neutron detector array at HRIBF S.N. Liddick, K. Rykaczewski, R. Lillie, M.J. Saltmarsh, J. Batchelder, S. Ilyushkin, J.A. Winger A new high-efficiency neutron detector array is being developed at the HRIBF to complement existing experimental equipment for the beta decay studies of neutron-rich fission fragments. The neutron detector array will consist of 2 foot long $^{3}$He tubes at 10 atmosphere surrounded by a polyethylene moderator. With an expected efficiency of $\sim$70\% the array will greatly aid in the determination of absolute beta-delayed neutron branching ratios when combined with the ``ranging-out'' of postaccelerated radioactive ion beams [1]. Geant4 [2] and MCNP calculations have been performed to simulate the efficiency of the array in a variety of geometries and results were compared to the efficiencies of existing neutron detectors. Simulation results will be presented. Work supported by DOE grants DE-AC05-00OR-22725, DE-AC05-76OR00033 and DE-FG02-96ER41006. \begin{thebibliography}{99} \bibitem{ref1} C.~J.~Gross, {\em et al.} Proc. of ENAM Conf., EPJDirect, in press (2005). \bibitem{ref2} S. Agostinelli, {\em et al.}, Nucl. Instrum. Methods Phys. Res. A506, (2003), 250. \end{thebibliography} [Preview Abstract] |
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