Time-resolved study of nonlinear photoemission in radio-frequency photoinjectors.

Photoemission is one of the fundamental processes that describes the generation of charged particles from materials irradiated by photons. The continuous progress in the development of ultrashort lasers allows investigation into the dynamics of the process at the femtosecond timescale. Here we report about experimental measurements using two ultrashort ultraviolet laser pulses to temporally probe the electrons release from a copper cathode in a radio-frequency photoinjector. By changing their relative delay, we studied how the release mechanism is affected by two-photon photoemission when tens of GW/cm2 intensities are employed. We evaluated the limits it poses on the achievable beam brightness and analyzed the resulting emission yield in terms of the electronic temperature by modeling the cathode as a two-temperature system.

Two-Color Radiation Generated in a Seeded Free-Electron Laser with Two Electron Beams.

We present the experimental evidence of the generation of coherent and statistically stable two-color free-electron laser radiation obtained by seeding an electron beam double peaked in energy with a laser pulse single spiked in frequency. The radiation presents two neat spectral lines, with time delay, frequency separation, and relative intensity that can be accurately controlled. The analysis of the emitted radiation shows a temporal coherence and a shot-to-shot regularity in frequency significantly enhanced with respect to the self-amplified spontaneous emission.

[Provision of artificial ventilation of the lungs during endolaryngeal surgical interventions using a high-energy laser]. / Obespechenie iskusstvennoi ventiliatsii legkikh pri éndolaringeal'nykh khirurgicheskikh vmeshatel'stvakh s ispol'zovaniem vysokoénergeticheskogo lazera.

To ensure controlled lung ventilation in endolaryngeal surgical interventions, using a high-energy laser, use was made of normal frequency jet ventilation (NFJV) and high frequency jet ventilation (HFJV) through a non-inflammable fluoroplast catheter supplied at a distal end with a device fixing it in a central position. HFJV seems preferable, as endolaryngeal manipulations become more convenient. The study was performed in 118 patients. Venturi effect was observed only during ventilation through a tracheostomic canule. It has been established that, unlike NFJV, in HFJV gas exchange parameters are much better, though oxygenation in NFJV is satisfactory in all the patients.