Effect of lift force on the aerodynamics of dust grains in the protoplanetary disk

We newly introduce lift force into the aerodynamics of dust grains in the protoplanetary disk. Although many authors have so far investigated the effects of the drag force, gravitational force and electric force on the dust grains, the lift force has never been considered as a force exerted on the dust grains in the gas disk. If the grains are spinning and moving in the fluid, then the lift force is exerted on them. We show in this paper that the dust grains can be continuously spinning due to the frequent collisions so that the lift force continues to be exerted on them, which is valid in a certain parameter space where the grain size is larger than ~ 1 m and where the distance from the central star is larger than 1 AU for the minimum mass solar nebula. In addition, we estimate the effects of the force on the grain motion and obtain the result that the mean relative velocity between the grains due to the lift force is comparable to the gas velocity in the Kepler rotational frame when the Stokes number and lift-drag ratio are both ~ 1. This estimation is performed under the assumptions of the steady state and the isotropic spin angular momentum. We also estimate the mean relative velocity when the grains keep spinning and conclude that the lift force marginally affects the mean relative velocity in the minimum mass solar nebula. If there is a grain-concentrated part in the disk, the relative velocity due to the lift force may dominate there because of high collision rate.Comment: 9 pages, 4 figures. Accepted for publication in Earth, Planets and Spac

Anomalies in the decay rates of antiprotonic helium-atom states

Six resonance transitions of the antiprotonic helium atom in helium gas at densities of 3*10/sup 20/-3*10/sup 21/ cm/sup -3/ were studied at the antiproton decelerator (AD) of CERN. The decay rates of the daughter states of these transitions were determined either from the time distributions of the resonance spikes or from the widths of the resonance lines. Whereas most of the observed decay rates agree with theoretical calculations of Auger rates, two states, (n, l)=(37,33) and (32,31), were found to have decay rates two orders of magnitude larger than predicted by these calculations. The effect of coupling with near-lying electron-excited states is considered to be the reason for the anomaly of the (37, 33) state, as pointed out by Kartavtsev et al. Phys. Rev. A 61, 062507 (2000) (25 refs)

Hyperfine structure measurements of antiprotonic helium and antihydrogen

This paper describes measurements of the hyperfine structure of two antiprotonic atoms that are planned at the Antiproton Decelerator (AD) at CERN. The first part deals with antiprotonic helium, a three-body system of alpha-particle, antiproton and electron that was previously studied at LEAR. A measurement will test existing three-body calculations and may - through comparison with these theories - determine the magnetic moment of the antiproton more precisely than currently available, thus providing a test of CPT invariance. The second system, antihydrogen, consisting of an antiproton and a positron, is planned to be produced at thermal energies at the AD. A measurement of the ground-state hyperfine splitting, which for hydrogen is one of the most accurately measured physical quantities, will directly yield a precise value for the magnetic moment of the antiproton, and also compare the internal structure of proton and antiproton through the contribution of the magnetic size of the antiproton to the ground state hyperfine splitting.This paper describes measurements of the hyperfine structure of two antiprotonic atoms that are planned at the Antiproton Decelerator (AD) at CERN. The first part deals with antiprotonic helium, a three-body system of alpha-particle, antiproton and electron that was previously studied at LEAR. A measurement will test existing three-body calculations and may - through comparison with these theories - determine the magnetic moment of the antiproton more precisely than currently available, thus providing a test of CPT invariance. The second system, antihydrogen, consisting of an antiproton and a positron, is planned to be produced at thermal energies at the AD. A measurement of the ground-state hyperfine splitting, which for hydrogen is one of the most accurately measured physical quantities, will directly yield a precise value for the magnetic moment of the antiproton, and also compare the internal structure of proton and antiproton through the contribution of the magnetic size of the antiproton to the ground state hyperfine splitting.This paper describes measurements of the hyperfine structure of two antiprotonic atoms that are planned at the Antiproton Decelerator (AD) at CERN. The first part deals with antiprotonic helium, a three-body system of alpha-particle, antiproton and electron that was previously studied at LEAR. A measurement will test existing three-body calculations and may - through comparison with these theories - determine the magnetic moment of the antiproton more precisely than currently available, thus providing a test of CPT invariance. The second system, antihydrogen, consisting of an antiproton and a positron, is planned to be produced at thermal energies at the AD. A measurement of the ground-state hyperfine splitting, which for hydrogen is one of the most accurately measured physical quantities, will directly yield a precise value for the magnetic moment of the antiproton, and also compare the internal structure of proton and antiproton through the contribution of the magnetic size of the antiproton to the ground state hyperfine splitting.This paper describes measurements of the hyperfine structure of two antiprotonic atoms that are planned at the Antiproton Decelerator (AD) at CERN. The first part deals with antiprotonic helium, a three-body system of alpha-particle, antiproton and electron that was previously studied at LEAR. A measurement will test existing three-body calculations and may - through comparison with these theories - determine the magnetic moment of the antiproton more precisely than currently available, thus providing a test of CPT invariance. The second system, antihydrogen, consisting of an antiproton and a positron, is planned to be produced at thermal energies at the AD. A measurement of the ground-state hyperfine splitting, which for hydrogen is one of the most accurately measured physical quantities, will directly yield a precise value for the magnetic moment of the antiproton, and also compare the internal structure of proton and antiproton through the contribution of the magnetic size of the antiproton to the ground state hyperfine splitting.This paper describes measurements of the hyperfine structure of two antiprotonic atoms that are planned at the Antiproton Decelerator (AD) at CERN. The first part deals with antiprotonic helium, a three-body system of alpha-particle, antiproton and electron that was previously studied at LEAR. A measurement will test existing three-body calculations and may - through comparison with these theories - determine the magnetic moment of the antiproton more precisely than currently available, thus providing a test of CPT invariance. The second system, antihydrogen, consisting of an antiproton and a positron, is planned to be produced at thermal energies at the AD. A measurement of the ground-state hyperfine splitting, which for hydrogen is one of the most accurately measured physical quantities, will directly yield a precise value for the magnetic moment of the antiproton, and also compare the internal structure of proton and antiproton through the contribution of the magnetic size of the antiproton to the ground state hyperfine splitting.This paper describes measurements of the hyperfine structure of two antiprotonic atoms that are planned at the Antiproton Decelerator (AD) at CERN. The first part deals with antiprotonic helium, a three-body system of α-particle, antiproton and electron that was previously studied at LEAR. A measurement will test existing three-body calculations and may— through comparison with these theories— determine the magnetic moment $\mu _{\overline {\text{p}} }$of the antiproton more precisely than currently available, thus providing a test of CPT invariance. The second system, antihydrogen, consisting of an antiproton and apositron, is planned to be produced at thermal energies at the AD. A measurement of the ground-state hyperfine splitting $v_{{\text{HF}}} \left( {\overline {\text{H}} } \right)$, which for hydrogen is one of the most accurately measuredp hysical quantities, will directly yielda precise value for $\mu _{\overline {\text{p}} }$, andalso compare the internal structure of proton andan tiproton through the contribution of the magnetic size of the $\overline {\text{p}} {\mathbf{ }}{\text{to}}{\mathbf{ }}\nu _{{\text{HF}}} \left( {\overline {\text{H}} } \right)$

Subaru Hyper Suprime-Cam Survey for An Optical Counterpart of GW170817

We perform a $z$-band survey for an optical counterpart of a binary neutron star coalescence GW170817 with Subaru/Hyper Suprime-Cam. Our untargeted transient search covers $23.6$ deg$^2$ corresponding to the $56.6\%$ credible region of GW170817 and reaches the $50\%$ completeness magnitude of $20.6$ mag on average. As a result, we find 60 candidates of extragalactic transients, including J-GEM17btc (a.k.a. SSS17a/DLT17ck). While J-GEM17btc is associated with NGC 4993 that is firmly located inside the 3D skymap of GW170817, the other 59 candidates do not have distance information in the GLADE v2 catalog or NASA/IPAC Extragalactic Database (NED). Among 59 candidates, 58 are located at the center of extended objects in the Pan-STARRS1 catalog, while one candidate has an offset. We present location, $z$-band apparent magnitude, and time variability of the candidates and evaluate the probabilities that they are located inside of the 3D skymap of GW170817. The probability for J-GEM17btc is $64\%$ being much higher than those for the other 59 candidates ($9.3\times10^{-3}-2.1\times10^{-1}\%$). Furthermore, the possibility, that at least one of the other 59 candidates is located within the 3D skymap, is only $3.2\%$. Therefore, we conclude that J-GEM17btc is the most-likely and distinguished candidate as the optical counterpart of GW170817.Comment: 14 pages, 9 figures. Accepted for publication in PASJ (Publications of the Astronomical Society of Japan

Energetic ion confinement studies using comprehensive neutron diagnostics in the Large Helical Device

Understanding energetic particle (EP) confinement is one of the critical issues in realizing fusion reactors. In stellarator/helical devices, the research on EP confinement is one of the key topics to obtain better confinement by utilizing the flexibility of a 3D magnetic field. A study of EP transport in the Large Helical Device (LHD) has been performed by means of escaping EP diagnostics in hydrogen plasma operation. By starting deuterium operation of the LHD, the confinement study of EPs has progressed remarkably using newly developed comprehensive neutron diagnostics providing information for EPs confined in the core region. The total neutron emission rate (Sn) increases due to the relatively low deviation of the beam ion orbit from the flux surface with the inward shift of the magnetic axis. The Sn has a peak around the electron density of 2  ×  1019 m−3 to 3  ×  1019 m−3, as predicted. It is found that the fraction of beam–beam components in Sn is evaluated to be approximately 20% by the Fokker–Planck models TASK/FP in the plasma with both co- and counter-neutral beam injections. The equivalent fusion gain in DT plasma achieved 0.11 in a negative-ion-based neutral beam heated plasma. Time evolution of Sn following the short pulse neutral beam injection into the electron–cyclotron-heated low-beta plasma is reproduced by drift kinetic simulation, indicating that transport of a beam ion injected by a short pulse neutral beam can be described with neoclassical models in magnetohydrodynamic quiescent low-beta plasmas. The vertical neutron camera works successfully, demonstrating that in the co-neutral beam-injected plasma, the neutron emission profile shifts according to the magnetic axis position. The shift of the neutron emission profile is reproduced by orbit-following models. The triton burnup study is performed for the first time in a stellarator/heliotron to understand the alpha particle confinement. It is found that the triton burnup ratio, which largely increases at inward-shifted configurations due to the better triton orbit and better plasma performance in the inward-shifted configuration, is similar to that measured in a tokamak having a similar minor radius to the LHD. We study the confinement capability of EPs toward a helical reactor in the magnetohydrodynamic quiescent region and expansion of the energetic ion physics study in toroidal fusion plasmas