Electron-bunch lengthening on higher-harmonic oscillations in storage-ring free-electron lasers.

The influence of higher-harmonic free-electron laser (FEL) oscillations on an electron beam have been studied by measuring its bunch length at the NIJI-IV storage ring. The bunch length and the lifetime of the electron beam were measured, and were observed to have become longer owing to harmonic lasing, which is in accord with the increase of the FEL gain. It was demonstrated that the saturated FEL power could be described by the theory of bunch heating, even for the harmonic lasing.

A novel collagen hydrogel cross-linked by gamma-ray irradiation in acidic pH conditions.

We made a new type of collagen gel by gamma-ray irradiation of an acidic solution of type-I collagen, and performed comparative studies on a conventional gel and the new type of gel. The neutral gel, a conventional 0.3% (w/v) collagen gel, was formed at neutral pH and then irradiated by gamma-rays.

Gelatin hydrogels cross-linked by gamma-ray irradiation: materials for absorption and release of dye.

Gelatin hydrogels cross-linked by y-ray irradiation using 60Co as gamma-ray source were prepared. As a model of controlled release of low-molecular-weight compounds, absorption and release of methylene blue, a water-soluble cationic dye, was investigated. Irradiated gelatin hydrogels did not redissolve at temperatures over 40 degrees C, while unirradiated gels were thermoplastic and reversibly changed the stage between gel and sol.

Statistical image analysis of high-sensitivity neutron images obtained by cooled CCD systems.

Neutron sensitivity and noise characteristics of cooled CCD NR systems were investigated. Eighteen species of neutron sensitive scintillators were tested by the use of two types of cooled CCD devices. The statistical analysis of the S/N ratio of the neutron images showed that the ZnS+LiF type was the highest sensitivity scintillator.