120413457
Coherent bremsstrahlung from the internal target of the 1.3 GeV electron synchrotron
Abstract A Si single crystal has been mounted on the conventional internal target holder of the 1.3 GeV electron synchrotron at the Institute for Nuclear Study, Tokyo. The energy spectrum measured with the pair spectrometer has a clear enhancement due to the coherent bremsstrahlung process. The linear polarization of the photon beam thus obtained is estimated to be 27% and 10% at the photon energy of 200 and 540 MeV, 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.
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.
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.
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.
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.
118590299
Trapped, Two-Armed, Nearly Vertical Oscillations in Disks with Toroidal Magnetic Fields II: Effects of Finite Thickness
We examine the radial trapping of two-armed (m = 2) vertical p-mode oscillations in geometrically thin relativistic disks that are vertically isothermal, but terminated at a certain height by the presence of hot and low-density corona. The disks are assumed to be subject to toroidalmagneticfields. The oscillationsare classified by n, anumber related to the node number of oscillations in the vertical direction, and starting from n = 1. In modes with n = 1, the frequencies of trapped oscillations depend little on the height of termination, but in modes with n = 2, 3, ��� the frequencies decrease and the radial extentions of the trapped region become wide, as the termination height decreases. This study is a preparation to examine whether these oscillations can describe kilo-hertz quasi-periodic oscillations (kHz QPOs), horizontal branch oscillations (HBOs), and their correlations.
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.
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.
55477539
An idea of dynamical cooling of electron beam in SR ring
A beam cooling method which uses a stimulated emission of radiation by relativistic electrons in a magnetic field, is proposed to apply to an electron beam in synchrotron radiation rings. The simulation is produced by a traveling RF electric field in a transmission line against the beam. Averaging the emission power over electron energy distributions, the net emission from the beam is taken place in a certain frequency region. Some conditions for the energy emission are discussed. The emission power is shown to be enough large to decrease the horizontal emittance of the beam to a very small value in typical synchrotron radiation rings.<<ETX>>
7967891
Beam-beam effect observed in the KEKB
This report summarizes observed phenomena related to the beam-beam effects in the KEKB collider. A general performance of the beam-beam effect is described. An em- phasis is put on the reduction of the specific luminosity with shorter bunch spacing. ible with the present maximum beam current. The scrub- bing effect of the chamber wall also possibly contributed to suppress the blowup. The present beam current limitation comes from a heating problem in the IR region. Another feature of the KEKB is that working points are very close to the half integer resonance particularly in the horizontal direction as is seen in the table. These horizon- tal tunes make the horizontal emittance large and the hori- zonal beta functions small to a large extent. This large emit- tance compensates the large bunch currents and contributes to stabilize the beams against the beam-beam effect. As is seen in the table, both of the horizontal and vertical tunes of the both rings are located above the half integer resonance, while the vertical tunes are above the integer resonance in the design. In the early days of the KEKB, the vertical tunes were above the integer resonance. In February 2001, the vertical tunes moved to above the half integer based on results of new beam-beam simulations. This change of the tunes brought some increase of the luminosity.