119407416
Proton compton scattering at backward angles in the energy range from 400 MeV to 1050 MeV
Abstract Differential cross sections of proton Compton scattering have been measured in the energy range between 400 MeV and 1050 MeV at C.M.S. angles of 150° and 160°. The recoil proton was detected with a magnetic spectrometer using multi-wire proportional chambers and multi-wire spark chambers. The scattered photon was detected with a lead glass Cerenkov counter of the total absorptive type with two layers of multi-wire proportional chambers which measured the horizontal and vertical positions of the scattered photon. The proton Compton scattering was differentiated from the background of the π 0 photoproduction events with the use of angular correlations between the recoil proton and the scattered photon. The cross-section data show the clear second resonance peak at E γ = 750 MeV and a bump around E γ = 925 MeV at both angles. Also the angular distributions show the backward peak in the energy range between 700 MeV and 950 MeV. The data are compared with theoretical calculations based on an isobar model with some phases for the resonances. In this calculation, the proton Compton data were fitted varying the photocouplings of the nucleon resonances around the bump and the phases below the third resonances as free parameters. The calculation reproduced the angular distribution of differential cross sections well. However, it was inevitable that we use large photocouplings of P 33 (1600) in order to fit the bump.
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.
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.
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.
118371698
Electron Cloud Effects in the KEK‐PS and the KEK/JAERI Joint Project
An e‐p instability is potentially a serious problem for proton rings in JKJ, which forces us to study the e‐p instability in several high‐intensity proton rings. This work informs JKJ whether we have to take measures to cure the instability. A TiN coating on the chamber surface is one of remedies. Results of SEY measurements performed at KEK are discussed. The observation of electron cloud candidates at the KEK 12 GeV PS Main Ring is also presented.
13244089
Lattice diagnostics using single kick closed orbit at KEKB
We have measured beta functions using single kick closed orbit at KEKB. The measured beta functions were compared with the model lattice and gradient errors were extracted from the result in a beta beat. The gradient errors were also obtained by changing strength of steering magnets and measuring beam positions as the second method. The methods of the error estimation and preliminary results are reported.
135949224
Residual gas analysis and electron cloud measurement of DLC and TiN coated chambers at KEKB LER
For future high-intensity positron or proton accelerators, beam instability caused by electron cloud is one of the most important problems. Some coatings on inner surface of beam chambers with materials having low secondary emission yields such as titanium nitride (TiN), nonevaporable getter and so on have represented good effects against the electron cloud instability. In this study, diamond like carbon (DLC) and TiN coated chambers, and a copper chamber without coating were installed to an arc section of KEKB LER to make comparisons of total pressure, residual gas components and electron cloud activity during the beam operation under the same condition. Residual gas observation for the DLC coating revealed much higher hydrogen gas desorption because a process gas including hydrogen was used for the film growth. No remarkable hydrocarbon gas desorption was found. On the other hand, a mass peak of amu = 14, that is N was prominent in the TiN coating. The electron cloud activity in the DLC coating was lower than the TiN coating and the copper chamber.
113399696
Resonant Excitation of Disk Oscillations in Deformed Disks. V. Effects of Dissipative Process
It is suggested that a set of positive- and negative-energy oscillations can be resonantly excited in the inner region of deformed (warped or eccentric) relativistic disks. In this paper we examine how a dissipative process affects this wave excitation. The results show that when the resonant condition in frequency is roughly satisfied, and thus the oscillations are excited, the introduction of a dissipative process works so as to decrease the growth rate of the oscillations. When the frequency difference between the two oscillations is larger than a certain amount that is required by the resonant condition, however, the oscillations are excited by introducing a dissipative process. This excitation by the dissipative process can be understood as a special example of a double-diffusive instability.
123854343
GENERATION OF HIGH-ENERGY ELECTRON BEAM BY LASER-PLASMA ACCELERATOR
An energy gain of the monoenergetic component of electrons γ were successfully increased to 25 MeV by decreasing an electron density ne to 4 × 1019cm-3 and increasing a laser power PL to 4 TW. An empirical scaling law of the energy gain of γ ∝ PL/ne was derived from the experiment. A forward scattering spectrum of the laser pulse showed anti-Stokes satellite peaks up to third-order harmonics around a second harmonic light and a Stokes satellite peak around a laser wavelength, which indicated that a wakefield was excited in a self-modulation laser wakefield regime. A density modulation of wakefield was estimated at 60 ± 10 % from intensity ratios of satellite peaks. The empirical scaling law well agrees with results obtained at other institutes by using higher laser power of 10 ~ 30 TW.