120420501
Single charged pion photoproduction from carbon above 300 MeV
Abstract Momentum spectra of charged pions in photoproduction on carbon nuclei have been measured at a lab angle 28.4° for quasi-monochromatic photons of 50 MeV width in the energy range between 300 and 850 MeV. The behaviour of resulting cross sections is discussed.
121673805
Polarimeter System for High-Energy Protons Using Carbon Plate and Liquid Hydrogen
In order to measure recoil proton polarization for the reaction γ+p→π°+p in a wide energy range, a polarimeter system has been constructed using carbon plate and liquid hydrogen as the scatterer. It consists of multi-wire proportional chambers, wire spark chambers, scintillation counter hodoscopes, and scatterers. Carbon plates for lower energy protons and liquid hydrogen for higher-energy protons were used as scatterers. The liquid-hydrogen polarimeter has worked reliably in continuous operation for a long time. The performance of the system in the experiment is described.
123100999
Differential cross sections of neutral pion photoproduction from hydrogen in the energy region from 390 MeV to 975 MeV
The differential cross sections of the reaction γp→π0p have been measured at photon energies between 390 MeV and 975 MeV with an energy step of 20 or 25 MeV. The angular region covers 11 angles between 15° and 130° in the c.m.s. A combination of a magnetic spectrometer and photon detector was used for the measurement in the angular region from 50° to 130°. At forward angles of 15°, 35° and 50°, π0 mesons were detected using a π0 detector consisting of a pair of photon detectors. The data obtained with two different detection systems overlap at the angle of 50° and coincide with each other within the experimental error. The results are compared with those of phenomenological partial-wave analyses.
121021517
A honeycomb sandwich structure vacuum jacket for cryogenic targets
Abstract Cryogenic targets (H 2 , D 2 and 4 He) have been built for use in the study of photonuclear reactions with a π sr spectrometer, TAGX, at the 1.3 GeV Tokyo electron synchrotron. A new type of vacuum jacket, fabricated from plastic honeycomb core and Mylar skins, has been used in the target system for more than 5000 hours. The average radiation thickness and the average density of this jacket are measured to be 3.3 × 10 −3 X 0 and 0.15 g/cm 3 , respectively.
3231612
Neutral-pion photoproduction on the deuteron.
Large-angle cross sections for ..gamma..d..--> pi../sup 0/d are systematically measured in a photon energy range between 500 and 1000 MeV. A good fit is obtained by use of a Glauber model calculation which includes the dibaryon resonances /sup 3/F/sub 3/(2.26) and /sup 1/G/sub 4/(2.51), but the fit has an unusual nature in the role of resonance and nonresonance contributions.
119906527
MEASUREMENT OF THE POLARIZATION PARAMETER IN BACKWARD $pi$$sup +$p ELASTIC SCATTERING AT 1.60, 1.80, 2.11, AND 2.31 GeV/c.
118498018
An Attempt to Describe Frequency Correlations among kHz QPOs and HBOs by Two-Armed Nearly Vertical Oscillations
We examine whether the two-armed ($m=2$) vertical p-mode oscillations trapped in the innermost region of magnetized accretion disks with finite disk thickness can describe kHz QPOs and HBOs in LMXBs. First, we derive the frequency-frequency correlation of the two basic oscillations (both are fundamental modes in the vertical direction, but one is the fundamental and the other the first overtone in the radial direction), and compare it with the observed frequency correlation of twin kHz QPOs. Results show that the calculated frequency correlation can well describe observed correlation with reasonable values of parameters. Second, we examine whether the observed frequency correlation between kHz QPOs and HBO can be described by regarding HBO as the first overtone oscillation in the vertical direction (and the fundamental in the radial direction). The results suggest that i) innermost parts of disks on the horizontal branch are strongly diminished in their vertical thickness (presumably by hot coronae) and ii) the branch is roughly a sequence of variations of magnetic fields or disk temperature.
121990337
Commissioning of KEKB
KEKB has been operated since December, 1998, to deliver BB pairs for a physics detector. In this paper,we describe the commissioning procedure of KEKB.
22610759
Correlated Frequency-Changes of Trapped Vertical p-mode Oscillations and kHz QPOs
AbstractWe have examined the frequencies of trapped two-armed (m = 2) nearly verticaloscillations (vertical p-mode) in vertically isothermal disks with toroidal magneticﬁelds. The magnetic ﬁelds are stratiﬁed so that the Alfv´en speed, c A , is constant inthe vertical direction. We have particularly focused our attention on how frequenciesof the fundamental mode (n r = 0) and ﬁrst overtone (n r = 1) in the radial directionchange with correlation, when theratioc 2A /cs changes, c s beingthe isothermal acousticspeed. The results show that in the case where the oscillations are fundamentalmode (n=1) in the vertical direction, the correlated frequency changes of the above-mentioned oscillations seem towell describe, withstandard values ofthe mass andspinof the central sources, the frequency correlation of kHz QPOs observed in neutron-starX-ray binaries.Key words:accretion, accrection disks — quasi-periodic oscillations — verticalp-mode oscillations — waves — X-rays; stars1. IntroductionMany authors now think that the kilo-hertz quasi-periodic oscillations (kHz QPOs) ob-served in low-mass X-ray binaries (LMXBs) are some kinds of disk oscillations in a strong gravi-tational ﬁeld. Understanding their origin is of importance, since it will become a promising toolto evaluate the mass and spin of the central sources as well as the disk structure surrounding thesources. Many models of kHz QPOs related to disk oscillations and waves have been proposed.None of them, however, can suﬃciently well describe the observed frequency correlation of thetwin kHz QPOs (Lin et al. 2010).As one of possible models of kHz QPOs, for example, we proposed a disk-oscillationmodel in deformed disks (Kato and Fukue 2006), based on the fact that in deformed disks aset of oscillations with positive and negative wave energies are excited resonantly (Kato 2004,1
120600649
Field emission from carbon nanotubes in DC and pulsed mode
Abstract Multi-wall Carbon Nanotube (CNT) emitters were tested in a combined diode-RF electron gun. Field emission of the nanotubes was observed at 5–30 MV/m, using a 250 ns FWHM long pulse with a peak voltage of 80–470 kV. The field emission threshold is compatible with that found from previous DC testing. We have extracted from a continuous field emitter up to a nanoCoulomb of charge and measured an emittance of 4 mm mrad with a 2 pC electron beam. The total charge emission during RF operation, using the 1.5 GHz, 2 cell RF structure, was found dependent on its period. RF operation showed that back bombarding electrons with up to 5 MeV did not impair the emission stability of the CNTs.
24439340
Direct electron acceleration by stochastic laser fields in the presence of self-generated magnetic fields.
A simple direct acceleration model is proposed, taking into account the stochastic phase disturbance of the coherent driving laser fields. A relativistic single particle simulation shows that plasma electrons are efficiently accelerated far above the ponderomotive energy. The energy and momentum distributions of the accelerated electrons are derived to examine the effects of the self-generated magnetic field on the characteristics of the electron beams. In addition to the beam collimation effect, the magnetic field is found to further enhance the electron acceleration, resulting in the generation of ultrahigh energy electrons.