Pulsed UCN production using a Doppler shifter at J-PARC

We have constructed a Doppler-shifter-type pulsed ultra-cold neutron (UCN) source at the Materials and Life Science Experiment Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC). Very-cold neutrons (VCNs) with 136-$\mathrm{m/s}$ velocity in a neutron beam supplied by a pulsed neutron source are decelerated by reflection on a m=10 wide-band multilayer mirror, yielding pulsed UCN. The mirror is fixed to the tip of a 2,000-rpm rotating arm moving with 68-$\mathrm{m/s}$ velocity in the same direction as the VCN. The repetition frequency of the pulsed UCN is $8.33~\mathrm{Hz}$ and the time width of the pulse at production is $4.4~\mathrm{ms}$. In order to increase the UCN flux, a supermirror guide, wide-band monochromatic mirrors, focus guides, and a UCN extraction guide have been newly installed or improved. The $1~\mathrm{MW}$-equivalent count rate of the output neutrons with longitudinal wavelengths longer than $58~\mathrm{nm}$ is $1.6 \times 10^{2}~\mathrm{cps}$, while that of the true UCNs is $80~\mathrm{cps}$. The spatial density at production is $1.4~\mathrm{UCN/cm^{3}}$. This new UCN source enables us to research and develop apparatuses necessary for the investigation of the neutron electric dipole moment (nEDM).Comment: 32 pages, 15 fugures. A grammatical error was fixe

Possible Cobalt-Cobalt Bridging by a Hemiacetal in the Dinuclear Cobalt Complex Bearing the Ligand Bis(3-(2-pyridylmethyleneamino)phenyl) Sulfone

A dinuclear cobalt complex bearing the ligand bis(3-(2-pyridylmethyleneamino)phenyl) sulfone (BPMAPS) was prepared. It is proposed that the structure of this is [Coz(BPMAPS)(m-0AcMhemi-Et)]PF6 wherein the cobalt centers are bridged by two carboxylato groups in m-fashion and a hemiacetal with an ethoxy group (hemi-Et). This proposal is based on the similarity of the FT-IR, UV-Vis, and FAB-MS results with the crystallographically characterized dinuclear manganese complex [Mn2(BPMAPS)(m-OAcMhemi-Me)]PF6, and elemental analysis results

Sympathetic Cooling of Trapped Cd+ Isotopes

We sympathetically cool a trapped 112Cd+ ion by directly Doppler-cooling a 114Cd+ ion in the same trap. This is the first demonstration of optically addressing a single trapped ion being sympathetically cooled by a different species ion. Notably, the experiment uses a single laser source, and does not require strong focusing. This paves the way toward reducing decoherence in an ion trap quantum computer based on Cd+ isotopes.Comment: 4 figure

Meridional Distribution of Middle-Energy Protons and Pressure-Driven Currents in the Nightside Inner Magnetosphere: Arase Observations

We examined the average meridional distribution of middle‐energy protons (10–180 keV) and pressure‐driven currents in the nightside (20–04 hr magnetic local time) ring current region during moderately disturbed times using the Arase satellite\u27s data. Because the Arase satellite has a large inclination orbit of 31°, it covers the magnetic latitude (MLAT) in the range of −40° to 40° and a radial distance of <6RE. We found that the plasma pressure decreased significantly with increasing MLAT. The plasma pressure on the same L* shell at 30° < MLAT < 40° was ∼10–60% of that at 0° < 4 MLAT < 10°, and the rate of decrease was larger on lower L* shells. The pressure anisotropy, derived as the perpendicular pressure divided by the parallel pressure minus 1, decreased with radial distance and showed a weak dependence on MLAT. The magnitude of the plasma beta at 30°<MLAT<40° was 1 or 2 orders smaller than that at 0°<MLAT<10°. The plasma pressure normalized by the value at 0°<MLAT<10° estimated from the magnetic strength and anisotropy was roughly consistent with the observed plasma pressure for L*=3.5–5.5. The azimuthal pressure‐gradient current derived from the plasma pressure was distributed over MLAT∼0–20°, while the curvature current was limited within MLAT∼0–10°. We suggest that the latitudinal dependence should be taken into account in interpretations of plasma parameters in successive orbits during magnetic storms

First molecular superconductor with the tris(oxalato)aluminate anion, β″-(BEDT-TTF)4(H3O)Al(C2O4)3·C6H5Br, and isostructural tris(oxalato)cobaltate and tris(oxalato)ruthenate radical cation salts

Peter Day’s research group reported the first molecular superconductor containing paramagnetic metal ions in 1995, β″-(BEDT-TTF)4(H3O)Fe(C2O4)3·C6H5CN. Subsequent research has produced a multitude of BEDT-TTF-tris(oxalato)metallate salts with a variety of structures and properties, including 32 superconductors to date. We present here the synthesis, crystal structure, and conducting properties of the newest additions to the Day series including the first superconductor incorporating the diamagnetic tris(oxalato)aluminate anion, β″-(BEDT-TTF)4(H3O)Al(C2O4)3·C6H5Br, which has a superconducting Tc of ~2.5 K. β″-(BEDT-TTF)4(H3O)Co(C2O4)3·C6H5Br represents the first example of a β″ phase for the tris(oxalato)cobaltate anion, but this salt does not show superconductivity

Off-equatorial Pi2 pulsations Inside and Outside the plasmapause observed by the Arase satellite

Using magnetic field and electron density data from the Arase satellite for the period from March 2017 to September 2019, we investigate the spatial properties of Pi2 pulsations in relation to the plasmapause over a wide latitudinal range (absolute magnetic latitude, |Mlat|, 0.7) with Pi2 pulsations in the north-south (H) component at low-latitude ground stations on the nightside, are dominantly identified from the magnetic fields in the radial (BR) and compressional (BP) components when the satellite is in the pre-midnight sector. In particular, high-coherence BP events are distributed over wide L-values and latitudinal ranges on the nightside in the pre-midnight sector. We identify the location of the plasmapause using the electron densities measured by Arase, and found that the BP-H power ratio and the cross phases of the high-coherence events show a gradual peak and a clear phase change from 0° to 180° in the vicinity of the plasmapause, respectively. These features indicate that mid- and low-latitude Pi2 pulsations on the nightside are excited by the plasmaspheric virtual resonance mode

Arase Observation of the Source Region of Auroral Arcs and Diffuse Auroras in the Inner Magnetosphere

Auroral arcs and diffuse auroras are common phenomena at high latitudes, though characteristics of their source plasma and fields have not been well understood. We report the first observation of fields and particles including their pitch‐angle distributions in the source region of auroral arcs and diffuse auroras, using data from the Arase satellite at L ~ 6.0–6.5. The auroral arcs appeared and expanded both poleward and equatorward at local midnight from ~0308 UT on 11 September 2018 at Nain (magnetic latitude: 66°), Canada, during the expansion phase of a substorm, while diffuse auroras covered the whole sky after 0348 UT. The top part of auroral arcs was characterized by purple/blue emissions. Bidirectional field‐aligned electrons with structured energy‐time spectra were observed in the source region of auroral arcs, while source electrons became isotropic and less structured in the diffuse auroral region afterwards. We suggest that structured bidirectional electrons at energies below a few keV were caused by upward field‐aligned potential differences (upward electric field along geomagnetic field) reaching high altitudes (~30,000 km) above Arase. The bidirectional electrons above a few keV were probably caused by Fermi acceleration associated with the observed field dipolarization. Strong electric‐field fluctuations and earthward Poynting flux were observed at the arc crossing and are probably also caused by the field dipolarization. The ions showed time‐pitch‐angle dispersion caused by mirror reflection. These results indicate a clear contrast between auroral arcs and diffuse auroras in terms of source plasma and fields and generation mechanisms of auroral arcs in the inner magnetosphere