Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session Y15: Mini-symposium on Optically Pumped Targets, Sources and Methods II |
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Sponsoring Units: DNP Chair: Thomas R. Gentile, National Institute of Standards and Technology Room: Key 11 |
Tuesday, April 14, 2015 1:30PM - 1:42PM |
Y15.00001: Polarized He3 Ion Source for RHIC and eRHIC James Maxwell The addition of a polarized neutron beam source to the Relativistic Heavy Ion Collider at Brookhaven National Laboratory would present promising opportunities for the study of nucleon structure. Polarized neutron collision measurements of transverse spin asymmetries in Drell-Yan scattering would allow a search of the predicted sign switch for u and d quark flavors in the Sivers function. In a future electron-ion collider, precision tests of the Bjorken sum rule could be carried out with both proton and neutron beams. Polarized 3He offers an effective polarized neutron beam which is accessible with RHIC spin manipulation. We are developing such a source leveraging metastability exchange optical pumping of 3He and utilizing the existing Electron Beam Ionization Source at RHIC. We aim to deliver approximately $1.5 \cdot 10^{11}$ doubly ionized 3He atoms per pulse at 70\% polarization into RHIC. The source is under development at MIT and an initial test of the principle at BNL is under construction. The source design will be described and the status of the test summarized. [Preview Abstract] |
Tuesday, April 14, 2015 1:42PM - 1:54PM |
Y15.00002: TREX: A Proposed Search for T violation in Polarized Neutron Optics William Snow A discovery of time reversal violation in any hadronic system, no matter how complicated, is clearly of fundamental importance. It has been known for decades that certain heavy nuclei possess neutron p-wave resonances where parity-odd amplitudes from the hadronic weak interaction are amplified by several orders of magnitude. The same amplification mechanism works also for P-odd T-odd neutron-nucleus forward-scattering amplitudes. A transmission experiment to search for a P-odd and T-odd term in the forward neutron-nucleus scattering amplitude using polarized neutrons and polarized nuclear targets shares with electric dipole moments the property of being a null test for time reversal invariance. Continuing advances in the ability to produce eV neutron beams of high polarization using polarized $^{3}$He and in the ability to polarize macroscopic amounts of the relevant nuclei ($^{139}$La, $^{131}$Xe, $^{81}$Br) coupled with the appearance of bright pulsed spallation neutron sources make it timely to reconsider the scientific reach and potential of this approach. We present a conceptual design for such a measurement [1] along with an estimate of the scientific reach for an experiment done at the 0.7 eV resonance in $^{139}$La. \\[4pt] [1] J. D. Bowman and V. Gudkov, arXiv:1407.7004 [Preview Abstract] |
Tuesday, April 14, 2015 1:54PM - 2:06PM |
Y15.00003: A Metastability-Exchange Optical Pumping and Compression System using Polarized $^{3}$He for a Proposed Laboratory Search for Neutron Monopole-Dipole Interactions Erick Smith $^{3}$He nuclei polarized using the metastability-exchange optical pumping (MEOP) method have been used for scientific applications such as magnetometry in space, neutron polarization and analysis, and medical imaging. In this talk we explain how this technique is also well-suited for a proposed experiment [1] to search for possible monopole-dipole interactions of polarized $^{3}$He nuclei with matter. The P-odd and T-odd monopole-dipole potential proposed by Moody and Wilczek [2] is proportional to $\vec{s} \cdot \vec{r}$ where $\vec{s}$ is the $^{3}$He spin and $\vec{r}$ is the separation between the particles. It can be induced by axions, and ARIADNE proposes to perform NMR on a polarized $^{3}$He ensemble at 4K with a radially-slotted tungsten disk spinning at a multiple of the $^{3}$He Larmour frequency to induce a resonant monopole-dipole perturbation. The radial slot length variations are chosen to maximize sensitivity to a monopole-dipole interaction range corresponding to the axion window. We describe the advantages that MEOP presents for this experiment and describe the MEOP-based polarized $^{3}$He gas compression system at Indiana University [3].\\[4pt] [1] A. Arvanitaki, A Geraci, PRL 113 161801 (2014)\\[0pt] [2] J. Moody, F Wilczek, PRD 30 130\\[0pt] [3] D. Hussey et al, RSI 76, 053503 (2005 [Preview Abstract] |
Tuesday, April 14, 2015 2:06PM - 2:18PM |
Y15.00004: JLab Polarized $^3$He Target Upgrade Kai Jin The polarized $\mathrm{^{3}He}$ target is being upgraded for the upcoming 12 GeV experiments at Jefferson Lab. The target is based on optical pumping of an alkali vapor and the subsequent spin exchange between the polarized alkali atoms and the $\mathrm{^{3}He}$ nuclei. In the upgrade, we aim to increase the luminosity by a factor of 2 in the first stage, from $\mathrm{1\times10^{36}\ cm^{-2}s^{-1}}$ to $\mathrm{2\times10^{36}\ cm^{-2}s^{-1}}$, and another factor of 3 in the second stage, to $\mathrm{6\times10^{36}\ cm^{-2}s^{-1}}$, while maintaining a maximum in-beam polarization of 60\% or higher. In order to achieve a higher polarization with high beam current, a newly-designed convection cell filled with a Rb-K mixture is adopted. Narrow line-width diode lasers are also used to obtain higher optical-pumping efficiency. Tests to reach the upgrade goals are on-going. The details of the plan, progress and preliminary results of the upgrade will be presented in this talk. [Preview Abstract] |
Tuesday, April 14, 2015 2:18PM - 2:30PM |
Y15.00005: Polarimetries for the Polarized $^3$He Target at JLab Nguyen Ton At Jefferson Lab, a Polarized $^3$He Target has been used as an effective polarized neutron target for studying nucleon spin structure. For the 12 GeV program at JLab, the first stage upgrade of the target aim to increase luminosity by a factor of 2 (to luminosity $\sim2\times 10^{36} cm^{-2} s^{-1}$) while keep maximum in-beam polarization at 60$\%$ with 30 $\mu$A beam current and reach a systematic uncertainty of polarimetry below 3$\%$. During the 6 GeV era, the target polarization was measured by two polarimetries: adiabatic fast passage-nuclear magnetic resonance (AFP-NMR) and electron paramagnetic resonance (EPR). With the upgrade, a new polarimetry, Pulse-NMR, is being studied in the lab for the up-coming metal coated target. In this talk, we will discuss the detail study of AFP-NMR, EPR, Pulsed-NMR measurements and their corresponding uncertainties. [Preview Abstract] |
Tuesday, April 14, 2015 2:30PM - 2:42PM |
Y15.00006: Incorporating Metal into Polarized $^{3}$He Target Cells Daniel J. Matyas, Maduka M. Kaluarachchi, Sumudu K. Katugampola, Yunxiao Wang, Vladimir Nelyubin, William A. Tobias, Gordon D. Cates Historically, high-pressure gaseous polarized $^{3}$He targets at Jefferson Lab (JLab) have utilized ``target cells'' fabricated entirely out of glass. With the 12 GeV upgrade nearing completion, experiments requiring significantly higher luminosities are planned, and to meet the challenge, metal end windows are being developed through which the electrons will enter and exit the target cell. The polarization technique used in $^{3}$He targets at Jefferson Lab utilizes spin-exchange collisions between $^{3}$He atoms and alkali-metal atoms polarized through optical pumping. Unfortunately, relatively few studies have investigated the spin relaxation of nuclear-polarized noble gases on metal surfaces, particularly under the conditions in our targets. We have tested various cells incorporating both glass and metal and have found that acceptable spin-relaxation rates can be obtained by electroplating gold coatings on OFHC copper substrates. Initial tests using titanium substrates, a better material for end windows, have not yet been as successful as copper ones. These studies have produced multiple cells that demonstrate the viability of $^{3}$He targets incorporating metal windows into their design. [Preview Abstract] |
Tuesday, April 14, 2015 2:42PM - 2:54PM |
Y15.00007: ABSTRACT WITHDRAWN |
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