Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session MJ: Mini-Symposium on Fundamental Neutron Physics VI |
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Chair: Beatrice Franke, TRIUMF Room: Hilton Kona 5 |
Saturday, October 27, 2018 2:00PM - 2:15PM |
MJ.00001: Cryogenic Design for TUCAN's New UCN Source Ryohei Matsumiya A precision measurement of the neutron electric dipole moment (nEDM) is a good probe to search for new sources of CP violation and to solve puzzles which cannot be explained by the standard model. TUCAN (TRIUMF Ultra-Cold Advanced Neutron source) is an international collaboration between Canada and Japan, aiming to measure the nEDM at a sensitivity of 10-27 ecm, a factor 30 better than the current limit, using a high intensity ultra-cold neutron (UCN) source. The TUCAN collaboration recently succeeded in producing the first UCN in Canada using a prototype UCN source installed on a dedicated proton beam line at TRIUMF. Our UCN source is based on a unique combination of a spallation neutron target and a superfluid helium (He-II) UCN converter. Following the success of this UCN source, the TUCAN collaboration is designing a considerably higher intensity UCN source based on the same combination. The new cryostat design will allow for operation at larger proton beam currents on the spallation target in order to achieve the necessary statistical sensitivity. |
Saturday, October 27, 2018 2:15PM - 2:30PM |
MJ.00002: Magnetic Field Monitoring in the SNS Neutron EDM Experiment Alina Aleksandrova for the SNS nEDM Collaboration A central problem to all neutron EDM experiments is the generation of a highly uniform and stable magnetic field. Because the suppression of systematic effects that arise from magnetic field nonuniformities and temporal drifts is vital to the success of these experiments, it is important to have the ability to precisely control and monitor the magnetic field gradients inside of the experimental volume. However, it is not always possible to measure the field gradients within the region of interest directly. To remedy this issue in the Spallation Neutron Source neutron EDM experiment, we have designed a field monitoring system that will allow us to reconstruct the field gradients inside of the fiducial volume using noninvasive measurements of the field components at discrete locations external to this volume. Studies of a prototype probe array consisting of ~30 cryogenic-compatible, single-axis fluxgate magnetometer sensors will be presented in this talk along with the characterization of these sensors at cryogenic temperatures. |
Saturday, October 27, 2018 2:30PM - 2:45PM |
MJ.00003: Abstract Withdrawn
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Saturday, October 27, 2018 2:45PM - 3:00PM |
MJ.00004: Development of Homogeneous Magnetic Field for the Measurement of Neutron EDM Kensaku Matsuta, Yasuhiro Masuda, Mototsugu Mihara Toward measurement of nEDM (neutron electric dipole moment) using polarized UCN from the UCN source, we are developing a magnetic field with high homogeneity for Ramsey resonance. Our goal is to measure nEDM with the 10 times better precision than the present world record. We are now developing an active filed compensation system to cancel out relatively high magnetic field from environment including the geomagnetism, as a preparation for a homogenous magnetic field by the spherical coils. Our half scale test system is 2m x 2m x 2m in size, and is composed of 4 square coils in one direction, and can be graded up to 3D system which is composed of 12 coils in total. Using signals from magnetic field sensors in feed back loops, our system automatically cancels out both the center magnetic field and the field gradient at the same time. Distance between coils are optimized for the better magnetic field homogeneity. We report present status of the development, including performance, e.g., field suppression factor, time response, field homogeneity, etc.
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Saturday, October 27, 2018 3:00PM - 3:15PM |
MJ.00005: In Situ Magnetic Field Mapping System for the LANL Neutron EDM Experiment Jared Brewington behalf of the LANL-nEDM Collaboration The LANL neutron electric dipole moment (LANL-nEDM) experiment requires precise knowledge of the magnetic field within the fiducial volume. In the experiment, a high-uniformity magnetic field coil mounted within a multi-layer magnetic shield house provides for the static $B_0$ magnetic field. We have designed and installed an in situ magnetic field mapping system which permits for automated, remotely-controlled measurements of the $B_0$ magnetic field within the shield house. The system is capable of full three-dimensional motion, and can either carry out measurements of the field within the measurement cell volume (e.g., when the measurement cell is not installed) or can provide for periodic monitoring of the field at a large number of positions external to the measurement cell with the measurement cell in place. In this talk, results from initial testing of the system will be presented. |
Saturday, October 27, 2018 3:15PM - 3:30PM |
MJ.00006: Spin Dressed Relaxation and Frequency Shifts from Field Imperfections. Christopher Swank, Ezra Webb, Xiaoling Liu, Bradley Filippone Critical dressing, the simultaneous dressing of two spin species to the same effective Larmor frequency, in principle, maximizes the sensitivity of the nEDM@SNS. The benefits of critical dressing are achieved at the expense of generating a large uniform oscillating field. Due to inevitable imperfections of the fields generated, the benefits of spin dressing may be lost from additional relaxation and noise. In this analysis the subject of relaxation and frequency shifts of neutrons and 3He in a spin dressing field are approached with simulations and theory. Analytical predictions are made from a new quasi-quantum model that includes gradients in the holding and dressing fields. The results are compared with a Monte Carlo simulation coupled with a 5th order Runge-Kutta integrator. Comparisons are presented as well as a set of optimized parameters that produce stable critical dressing for a range of dressing frequencies, as well as pulsed modulation parameters for maximum sensitivity. |
Saturday, October 27, 2018 3:30PM - 3:45PM |
MJ.00007: A Resonance Guide for eV Neutrons William Snow, Kylie Dickerson, Jesse Devaney Neutron mirrors function like optical fibers, allowing for low-loss transport of neutrons over long distances. Multilayer supermirror neutron optics works very well for cold neutrons, but their transverse phase space acceptance is too small to make them useful for eV energy neutrons. In this talk we present some ideas for eV neutron guides which use the large imaginary part of the neutron optical potential for neutron reflection. We evaluate the performance of a neutron mirror made of boron carbide enriched in 10B. We also present some possibilities for a neutron guide made of a cocktail of heavy nuclei, where the neutrons would bounce off of a "forest" of neutron-nucleus resonances. |
Saturday, October 27, 2018 3:45PM - 4:00PM |
MJ.00008: Behavior of Neutron Spin in Polarized Nuclear Target for the T-violation Search in Compound Nuclei Hirohiko Shimizu Small admixture of the weak interaction in the effective nucleon-nucleon interaction is extremely enhanced in the parity violating asymmetry in some of p-wave compound nuclear states induced by epithermal neutrons. Recent measurements of the spectroscopic factors in the entrance channel to the compound states support that the enhancement is caused as the result of the interference between the p-wave compound state and neighboring s-wave states. The fact suggests a new type of the extremely sensitive search for T-violation in the meson-nucleon coupling. The new search would be experimentally realized as the observation of neutron spin behavior on transmission through a polarized nuclear target. The behavior of neutron spin has been discussed at the lowest order approximation by employing the neutron forward scattering amplitude f defined as |
Saturday, October 27, 2018 4:00PM - 4:15PM |
MJ.00009: Development of polarized nuclear targets using dynamic nuclear polarization of mechanically ground nano-particles dissolved in ethanol matrix with TEMPO Takahiro Endo, Takahiro Iwata, Daisuke Kaneko, Daisuke Miura, Yoshiyuki Miyachi, Genki Nukazuka, Hikari Wauke La-139 is one of the candidates for the polarized nuclear targets in the T-violation measurement experiment, NOPTREX at J-PARC. Dynamic Nuclear Polarization (DNP) of LaAlO3 crystal achieved rather high polarizations of La-139, up to +47.5 % and -56.5 %. However, there are technical difficulties on growing a large crystal with good purity, controlling the density of the polarized agency Nd3+, and handling of the target material, whose crystal axis must be aligned with a magnetic field for DNP. In order to overcome these difficulties, we propose an alternative and simple method, which can be widely applied for polarizing the nuclei in other materials. LaF3 was ground into nanoparticles with a size of 30 nm at maximum by using a planetary ball-milling machine. The nanoparticles were dispersed in an ethanol matrix containing a free radical, TEMPO. At a magnetic field of 2.5 T and temperature of 0.9K, DNP of the nanoparticles was performed. The polarization of F-19 in the nanoparticles reached about 3 %, which was 2/3 as high as those for H-1 in the ethanol. The polarization difference may indicate polarization mechanism. Details of the target material preparation and results of the DNP test will be presented. |
Saturday, October 27, 2018 4:15PM - 4:30PM |
MJ.00010: Abstract Withdrawn
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(Author Not Attending)
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MJ.00011: Compensation of Magnetic Fields at the TRIUMF nEDM Experiment Shomi Ahmed The existence of a non-zero neutron electric dipole moment (nEDM) would violate parity and time-reversal symmetry. Extensions to the Standard Model predict the nEDM to be 10−26 - 10−28 e-cm. The current best upper limit set by Sussex/RAL/ILL nEDM experiment is 3.0×10−26 e-cm. The nEDM experiment at TRIUMF is aiming at the 10−27 e-cm sensitivity level. We are developing the world’s highest density source of UCN. The experiment requires a very stable (< pT) and homogeneous (< nT/m) magnetic field (B0) within the measurement cell. My involvement in the nEDM experiment is the development of active magnetic shielding to stabilize the external magnetic field by compensation coils. A prototype active magnetic shield has been tested at The University of Winnipeg. I will report on optimized experimental results from this prototype and its performance compared to the simulation study. Moreover, the magnetic environment at TRIUMF is more challenging than in our lab in Winnipeg, because of the closeness of the experiment to the TRIUMF cyclotron (B ~ 350 – 400 uT 'which is almost one order of magnitude larger than usual background fields’) and the changing environment with iron. Studies of the implementation at TRIUMF will also be reported. |
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