Performance of the ASTERIX III high power iodine laser
For more than 500 shots the 1 TW iodine laser Asterix III has demonstrated high reliability for light-plasma-interaction experiments. Improved laser parameters and new measurements of light pulse properties are reported.
Repetitively pulsed iodine laser with thermal gas flow cycle
The 1.315 mu m atomic iodine laser has been developed for repetitively pulsed operation by the use of a thermally driven fast gas flow and replenishment system. The flow, produced by thermal evaporation and condensation, removes the molecular iodine formed by photolysis which acts as a strong laser quenching agent. An all-glass construction of the laser and flow system gives long life sealed-off operation, and no iodine corrosion problems. Fluorocarbon buffer gases have been evaluated for use in providing flexibility in the operation of temperatures of the flow system in projected larger aperture oscillator systems, and for enhancing energy storage capability by pressure broadening the laser linewidth in Q-switched oscillators and amplifiers.
New Low-Profile Applicators for Local Heating of Tissues
A new type of low-profile applicator is described giving efficient power transfer to tissue with low leakage. It consists of a resonant element spaced from a ground plane by low-loss material having high relative permittivity and some relative permeability. This combination is covered by similar material which can be placed in direct contact with the tissue to be heated, or separated from it by a water bolus as required. Laboratory measurements using phantom materials show that these applicators are well matched and produce well defined and relatively uniform heating profiles. Applicators having maximum dimensions of 3-15 cm covering the frequency range 1000-100 MHz, respectively, are described. Penetration depths of at least 4 cm at 100-200 MHz are achieved. Tests on anesthetised pigs and some clinical assessment have confirmed the usefulness of this compact low-frequency type of applicator and have shown that performance compares favorably with that of other recently reported types. The design can be optimized for treatment of specific sites, and suitable choice of dimensions and electrical characteristics of the layer material allow the low-profile concept to be extended over a wide range of operating frequencies.