118539083
Simultaneous resonant excitation of low-frequency eccentric wave and tilt wave on tidally deformed disks
Simultaneous excitation of low-frequency eccentric precessing mode (one-armed p-mode) and tilt mode on tidally deformed disks is considered. If the orbit of the secondary star is eccentric and its orbital plane is misaligned with the disk plane of the primary, the above-mentioned two low-frequency oscillation modes are simultaneously excited on the primary disk, the former having prograte precession and the latter having retrograde precession. This excitation of disk oscillations is due to a wave–wave resonant excitation process considered by Kato (2013, PASJ, 65, 75). If parameter values relevant to Be/X-ray binary systems are adopted, the periods of these excited oscillations are around 10 times the orbital period of the secondary, which may be comparable with the timescale of giant outbursts observed in Be/X-ray systems.
16806997
Spin of Stellar-Mass Black Holes Estimated by a Model of Quasi-Periodic Oscillations
We have proposed in previous papers that the high-frequency pair of quasi-periodic oscillations observed in black-hole binaries with a frequency ratio of 3 : 2 are inertial-acoustic oscillations (nearly horizontal oscillations with no node in the vertical direction) or g-mode oscillations, which are resonantly excited on warped relativistic disks. The resonance occurs through horizontal motions. In this model, the dimensionless spin parameter, a∗ ,o f the central sources can be estimated when their masses are known from other observations. This estimate is done for
119286608
Resonant excitation of tilt mode in tidally deformed disks
In a previous paper (Kato 2013b), we have shown that in deformed disks a pair of trapped oscillation modes can be resonantly excited through couplings with disk deformation. In this paper we examine in what cases tilts are excited on tidally deformed disks by the above-mentioned wave-wave resonant process. The results show that tilts can be excited in various evolutional stages of tidally deformed disks, although the wave mode which becomes the pair to the tilt and the mode of tidal waves contributing to the resonance change by change of disk stages.
17631509
Quasi-Periodic Oscillations Resonantly Induced on Spin-Induced Deformed-Disks of Neutron Stars
We consider the situation where a spin-induced wavy perturbation is present on disks of neutron-star low-mass X-ray binaries. By non-linearly coupling with the perturbation, some modes of disk oscillations resonantly interact with the disks. We examine the resonant conditions under the assumption that the disks are vertically isothermal. The results show that when the spin frequency has some particular values, resonant coupling occurs at some radii. The modes and frequencies of these resonant oscillations are summarized. Some of these resonant oscillations seem to explain the frequencies of the observed kHz QPOs in objects of which the spin frequency is known.
14220941
Frequency Correlations of QPOs Based on a Disk Oscillation Model in Warped Disks
In previous papers, we proposed a model that high-frequency quasi-periodic oscillations (QPOs) observed in black-hole and neutron-star X-ray binaries are disk oscillations (inertial-acoustic and/or g-mode oscillations) resonantly excited on warped disks. In this paper we examine whether time variations of the QPOs and their frequenc yc orrelations observed in neutron-star X-ray binaries can be accounted for by this disk-oscillation model. By assuming that a warp has a time-dependent precession, we can well describe the observed frequency correlations among kHz QPOs and low-frequency QPOs over a wide range of frequencies.
19434452
Resonant excitation of disk oscillations in deformed disks. VII. Stability criterion in MHD systems
In a disk with an oscillatory deformation from an axisymmetric state with frequency ωD and azimuthal wavenumber mD, two normal mode oscillations with a set of frequency and azimuthal wavenumber being (ω1, m1) and (ω2, m2) are resonantly coupled to each other through the disk deformation when the resonant conditions (ω1 + ω2 + ωD = 0 and m1 + m2 + mD = 0) are satisfied. In the case of hydrodynamical disks, the resonance amplifies the set of the oscillations if (E1/ω1)(E2/ω2) > 0 (Kato 2013b, PASJ, 65, 75), where E1 and E2 are wave energies of the two oscillations with ω1 and ω2, respectively. In this paper we show that this instability criterion is still valid even when the oscillations are ideal MHD ones in magnetized disks, if the displacements associated with the oscillations vanish on the boundary of the system.
119388026
An observation of the SQS mode in a gas counter
Abstract The SQS mode has been observed with α-rays and a counter using 25 μm thick anode wire for comparatively simple gases, 95% Ar + 5% CO 2 , 90% Ar + 10% CH 4 , CO 2 , CH 4 and iso-C 4 H 10 . The curves of gas multiplication are presented.
121162987
Polarization of recoil protons from proton Compton scattering in the region of the second πN resonance
Abstract The polarization of recoil protons from proton Compton scattering has been measured at an angle of 90° c.m.s. in the region of the second nucleon resonance. The scattered photons were detected by a telescope which consisted of a lead plate converter, scintillation-counter hodoscopes and a Cerenkov counter, The angles and momenta of recoil protons were analyzed by a magnet with four spark chambers. The polarization of protons was obtained from the asymmetry in the elastic scattering of protons on carbon in a spark chamber. The polarization of recoil protons from proton Compton scattering are − 0.36 ± 0.29 and − 0.13 ± 0.29 at incident photon energies of 700 ± 50 and 800 ± 50 MeV, respectively. The polarization of recoil protons from neutral pion photoproduction is also obtained and the results are in good agreement with the previous data. A calculation of the polarization of recoil protons in the proton Compton scattering has been made by using an isobar model. The results of the calculation are consistent with the experimental data.
89614487
High energy electron acceleration by stochastic acceleration mechanism
A stochastic acceleration mechanism which explains the high energy electron acceleration by intense laser pulses is analyzed by Fokker‐Planck approach. The Fokker‐Planck equation describing is derived from the equation of motion of electrons interacting with filamented laser field. The time evolution of electron distribution function, energy distribution, effective temperature are obtained for initially rest plasma. The acceleration of 10 MeV electron beam is examined and shown to be effective.
120683961
Narrow Spacing Drift Chamber
Linearity and efficiency of a 3-mm spacing drift chamber was examined with an electron beam. A spatial coordinate is measurable with an accuracy of 0.2 mm.
55762967
Application of Electrochemical Buffing onto Niobium SRF Cavity Surface
Niobium electropolishing for SRF cavities are generally considered to be the best technology today. However, hydrofluoric and sulfuric acid mixture usually used in the EP process is harmful and requires us carefully controlled handling of it and the many additional facilities. In this article, we propose a new application of electrochemical buffing (ECB) to niobium SRF cavity. In the method of ECB, a rotating disk with abrasive fine particles where electrolyte is supplied is pressed against the workpiece. The disk and the work function as a cathode and an anode, respectively and an aqueous solution of sodium nitrate is used for the electrolyte. This technology brings us a couple of remarkable advantages like high etching rate, ultra small surface roughness, cost-effective and environment-compatible polishing.