[en] In the liquid waste disposal system in Monju, the concentrated liquid waste was alkaline. This phenomenon was remarkable when we treated the sodium deposit and aerosol, which were produced during the sodium leak accident. We took a close look at our treatment process and concluded that the decrease in the pH of the liquid waste was due to reaction with sodium hydroxide solution. Consequently we changed the chemical control value and improved the system processing in order to avoid producing the concentrated alkaline liquid waste. (author)

[en] We discuss the SU(2) chiral sigma model in the context of nuclear matter using a mean field approach at high density. In this model we include a dynamically generated isoscalar vector field and higher-order terms in the scalar field. With the inclusion of these, we reproduce the empirical values of the nuclear matter saturation density, binding energy, and nuclear incompressibility. The value of the incompressibility is chosen according to recently obtained heavy-ion collision data. We then apply the same dynamical model to neutronrich matter in beta equilibrium, related to neutron star structure. The maximum mass and corresponding radius of stable non-rotating neutron stars are found to be in the observational limit. (author)

[en] Back-illuminated CCD detectors have been used for visible, VUV and x-ray spectroscopy. The results are compared with those generated by conventional detection systems such as the photodiode array with image intensifier or micro-channel plate. The use of the back-illuminated CCD demonstrated excellent qualities including low noise, a high level of spectral resolution and a greatly extended output dynamic range. Detailed results of the comparison are also discussed. (author)

[en] The European Directive 96/12 requires that aircrew be considered as occupationally exposed persons and that measures are taken to determine the individual doses of air crew and cabin personnel. Consequently, several European research institutes have undertaken an extensive programme of air borne and mountain based experiments to measure the radiation field in the earth's atmosphere. Furthermore, Monte Carlo radiation transport calculations were done to follow the radiation cascades from the top of the atmosphere down to the earth's surface. Though the basic physical processes and radiation components have been studied previously, the determination of dose quantities require more physical information: Both operational (ambient dose equivalent) and risk related quantities (effective dose) contain non-physical information which is described by quality and radiation weighting factors, respectively. The radiation transport calculations show that at normal flight altitudes the spectral shapes of the particle fluences are essentially invariable. This permits to use calculated conversion coefficients to determine the dose quantities from calculated and experimental spectral data. This appears necessary especially for those radiation components whose dose contribution can not experimentally separated, but may considerably contribute to the effective dose considering the radiation factors presently recommended by the ICRP, e.g. for protons. The European Computer Package EPCARD for the Calculation of Aviation Route Doses was designed to combine the experimental and theoretical data in the best available way. The concept is to treat each major component of the cosmic rays separately, i.e. muons, electrons and photons, neutrons, protons and charged particles. The influence of geomagnetic shielding is considered based on calculations and experimental data, and the magnitude of solar modulation is inferred from neutron monitor data. Route doses are calculated along any specified aviation route and profile by integration along great circles. The essential characteristics of the programme are elucidated. Dose rate data are presented as obtained from measurements and calculations. (author)

[en] A photocathode RF-Gun was installed as a high quality electron source at JAERI-Kansai-APR for laser wakefield acceleration experiment. A charge of 730 pC was produced by a frequency quadrupled Nd:YLF laser whose energy was 60 μJ on a copper cathode surface. A photo-emitted charge increased as the RF-power increased. This enhancement of charge is known as Schottky effect. Quantum efficiency (QE) and a field emission dark current were measured during RF-conditioning. QE and the dark current were reduced with the progress of RF-conditioning after a leak of SF₆ gas. In order to reduce the dark current, the RF-conditioning is been continuing. (author)

[en] RF cavities for photocathode RF gun were built and tested by using high power RF up to 27 MW. The electric field gradient on the cathode reached 140 MW/m. During the RF conditioning, dark currents were measured for cavities with different surface treatments. A laser pulse was irradiated on a copper cathode and the photo-emitted beam was accelerated up to 3.2 MeV. An effective quantum efficiency of the cathode was obtained by changing laser power and field gradient. (author)

[en] The breakdown of the diodes and the resistors in the back-diode circuit, which is a protection against damages of the klystron and other elements, was found at the pulse modulator No.2 after a series of operations since 1997. The breakdown of the resistor can be explained by assuming a preceding breakdown of the diodes possibly suffered an excessive surge voltage. However, there has been no problem found in the back-diode circuit at the pulse modulator No.1. As one of efforts made at LEBRA of Nihon University to reduce the fluctuation of the energy and the current of the beam in the linac, an optimum reservoir voltage of the thyratron in each modulator has been investigated in order to reduce the fluctuation of the modulator output voltage between successive pulses. (author)

[en] The long pulse operation of the PV3030 klystron for FEL linac at LEBRA in Nihon University has been improved considerably by the additional vacuum system placed immediately downstream the klystron output rf window. With the new vacuum system, the large conductance has enabled a high vacuum in normal operation and a quick recovery when the dielectric breakdown occurred. A high vacuum near the rf window may be essentially important for a stable operation of the high power klystron with long pulse duration. Now the PV3030 klystron can be operated at the condition of 20 MW x 20 μs x 12.5 Hz. (author)

[en] A web-based system for browsing klystron histories and statistics has been developed for the KEKB e-/e+ linac. This system enables linac staffs to investigate various klystron histories, such as recent trends of ES (down frequency/reflection/high voltage), at his/her convenient PC/Mac/console, where a web-browser is available. This system started in January 2000, and now becomes an inevitable tool for the linac staffs. (author)

[en] In the control system at the KEK electron/positron linac, many VME-bus computers are employed to implement sub-systems for beam instrumentation and other general controls. These systems are utilized regularly from many operational programs too support the stable linac operation. In order to realize the robust and reliable operation by VME-bus computers, a distributed and redundant management environment was developed and used since the beginning of the KEKB commissioning. (author)