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>>
122032423
Experiences at the KEK B-factory vacuum system
121897579
Study of timing degradation and light attenuation in long plastic scintillation rods for time-of-flight counters in relativistic heavy ion experiments
Abstract We have studied the timing and light yield characteristics of long and thin scintillator samples of various sizes. Both the light yield and the time resolution degrade exponentially with respect to the distance from one end; the inverse slope parameters for the time resolutions are found to be twice those of the light yield. This is interpreted in terms of a photoelectron statistics picture, which can also explain the observed position dependence of time resolution for time-of-flight counters.
8862999
Recent progress of KEKB
We summarize the machine operation of KEKB during past one year focusing on progress for this period.
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.
86865953
Present Status of KEKB Vacuum System
The commissioning of KEKB (KEK B-factory) started in December 1998. The vacuum system has been working almost satisfactorily. The photon stimulated gas desorption coefficient of copper beam chamber is decreasing steadily and reached to about 2 - 4 × 10 -6
119944717
A large acceptance spectrometer using wire chambers
Abstract A large acceptance magnetic spectrometer has been constructed for an experiment on the π 0 -photoproduction off hydrogen and proton Compton scattering with the 1.3 GeV electron synchrotron at the Institute for Nuclear Study, University of Tokyo. The spectrometer system consists of four multiwire proportional chambers, six wire spark chambers and scintillation counters. The system has worked smoothly under high background events from electromagnetic processes. The performance, construction and monitoring system of the spectrometer are described.
121185850
New lead glasses for Cherenkov counters
Abstract Attempts have been made to improve the characteristics of glasses suitable for Cherenkov counters of the total-absorption type. Many kinds of new lead glasses were prepared and examined in the transmittance, radiation lengths, and methods of manufacturing. Several kinds of glass blocks having the dimension of 65 × 65 × 235 mm 3 were manufactured successfully. The transmittance of one of the new glasses is higher than the usual lead glass of F-2 ∗ . It was also found that the discoloration of the new glasses is smaller than the usual lead glasses upon irradiation of 60 Co γ rays of 10 4 to 10 7 Roentgens. The Cherenkov counters of the total-absorption type with the new glasses, together with the ones with usual lead glasses of F-2, SF-2, SF-5, and SF-6, were tested by using electron beams with energies from 300–1000 MeV. It was found that the energy resolution of the first ones is better by a few percents than that of the latter in the whole energy region.
120566869
The TOPAZ inner drift chamber
We have constructed a cylindrical drift chamber with anode and cathode delay-line readouts, which is the innermost tracking device of the TOPAZ detector. This inner drift chamber (IDC) is used for the tracking of charged particles in both rφ and rz planes. Fast track-finding logics have been developed for the event triggering. We describe the design, the construction and the performances of the IDC in the first beam run.
121847947
Neutrino mass studied by measuring tritium beta-decay with an iron-free beta-ray spectrometer
Abstract The second measurement of the neutrino mass at INS has been carried out. Combining the new data with the result of the first measurement, a preliminary upper limit of 25 eV at the 95% confidence level has been obtained for the neutrino mass from only statistical consideration.
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.