125039861
A superconducting spectrometer for the study of hypernuclei via (π, K+) reactions
SummaryA superconducting kaon spectrometer (INS-SKS) is under construction at Institute for Nuclear Study, University of Tokyo. The spectrometer, with 1/1000 momentum resolution and 100 msr acceptance, has been designed for intensive study of hypernuclei via (π, K+) reactions. It is to be installed in a new experimental hall of the KEK 12 GeV proton synchrotron and is scheduled to be ready for experiments by the end of 1990.RiassuntoUno spettrometro superconduttore a kaoni (INS-SKS) è in fase di costruzione all’Institute for Nuclear Physics dell’Università di Tokyo. Lo spettrometro, con una risoluzione di impulso di 1/1000 e accettanza 100 msr, è stato progettato per uno studio intensivo degli ipernuclei attraverso reazioni (π, K+). Dovrà essere installato in una nuova sala sperimentale del sincrotrone a protoni a 12 GeV del KEK e l’inizio degli esperimenti è previsto per la fine del 1990.РеэюмеВ институте ядерной фиэики при Токийском университете конструируется сверхпроводяший каонный спектрометр (INS-SKS). Спроектирован спектрометр с импульсным раэрещением 1/1000 и акцептансом 100 mcp для исследования гиперядер посредством (π, K+) реакций. Спектрометр смонтирован в новом зкспериментальном эале протонного синхротрона 12 ГзB в KEK. Начало зкспериментов планируется на конец 1990 г.
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.
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.
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.
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.
126057573
Study of vertical beam blowup in KEKB low energy ring
Vertical beam blowup has been observed in the KEKB low energy positron ring (LER) since early operation. The main characteristics of the blowup are explained by single-beam head-tail instability caused by an electron cloud. About 4600 solenoids were installed in the LER in order to remove the electrons. This paper describes the experimental study of the vertical beam blowup emphasizing the effect of the solenoids.
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.
17039539
Resonant Excitation of Disk Oscillations in Two-Armed-Deformed Disks and Application to High-Frequency QPOs
In previous papers we showed that in one-armed deformed disks, p-mode and g-mode oscillations are resonantly excited by horizontal resonance, and applied it to high-frequency quasi-periodic oscillations (QPOs) observed in lowmass X-ray binaries. In that model, the observed time variation of kHz QPOs is regarded as being the result of a timedependent precession of the deformation. In this paper we consider another possible cause of the time variation of kHz QPOs. That is, we demonstrate that in two-armed deformed disks, p-mode and g-mode oscillations are excited by a vertical resonance, not by a horizontal resonance (horizontal resonance dampens them). Furthermore, we show that in the case of a vertical resonance, the frequencies of excited disk oscillations can vary with time if the vertical disk structure changes with time. A brief application of these results to the time variation of observed kHz QPOs is discussed.
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.