Electron energy distributions have been measured in and near the negative glow of an abnormal glow discharge in helium at pressures in the range 3-25 Torr. The experimental technique involved the use of a differentially pumped retarding-field analyser. The measured distributions are distinctly non-Maxwellian. In particular, the distribution in the negative glow close to the cathode dark space shows a prominent 'tail' of high-energy electrons and a 'beam' component at the cathode fall potential ( approximately 300 V). The significance of these results for hollow cathode helium/metal-vapour lasers is discussed.

Instability mechanisms discussed to date are unable to account for the behavior of long-pulse self-sustained discharge-pumped XeCl devices. We develop theoretical arguments supporting the concept that halogen donor depletion during the discharge pulse is the principal cause of discharge collapse and the termination of lasing. The theoretical prediction that the duration of the glow phase should vary as the inverse square of the initial halogen donor concentration is verified by experimental results furnished by a study of a resistively stabilized long-pulse xenon chloride laser.

Results are presented on the ablation by 157 nm laser radiation of polytetrafluoroethylene (PTFE), polyimide, polyhydroxybutyrate (PHB), poly(methyl methacrylate) (PMMA), and poly(2-hydroxyethyl methacrylate) with 1% of ethylene glycol dimethacrylate as a crosslinking monomer. Direct photoetching of PHB and undoped PTFE is demonstrated for laser fluences ranging from 0.05 to 0.8 J/cm2. The dependence of the ablation process on the polymer structure is analyzed, and insight into the ablation mechanism is gained from an analysis of the data using Beer–Lambert’s law and the kinetic model of the moving interface. Consideration of the absorbed energy density required to initiate significant ablation suggests that the photoetching mechanism is similar for all the polymers studied.

Details of the design and operation of a simple, inexpensive, multiple anode-hollow cathode laser tube for CW helium-metal vapour laser systems are presented. The device is of metal construction and the component sections are connected by ordinary O ring couplings. To preserve the cleanliness of the system, helium from a high-pressure cylinder is slowly flushed through the tube. We have observed CW laser oscillation on a total of 39 lines in four helium-metal vapour systems (He-Cd, He-Zn, He-Se, He-I2) at wavelengths ranging from the near ultraviolet to the infrared, and output powers up to 25 mW/line. Operating characteristics of the laser are discussed for each system.

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