Plasma particle and energy reflection at a wall with an obliquely incident magnetic field

The particle and energy reflection coefficients are calculated for a plasma incident at a wall with an obliquely incident magnetic field. The salient result of these calculations is that the reflection coefficients can approach unity when the magnetic field is incident at grazing angles. This reflection of particles and energy will be an important process in determining the particle and energy balance in the edge plasma

Measurement of H/sub 2/, D/sub 2/ solubilities in Zr-Al

We have measured solubility constants for hydrogen and deuterium in the Zr-Al alloy to be: K/sub H/ = exp (11.1(5) - 16900(600)/T9 (Torr/(Torr-1/g)/sup 2/) and K/sub D/ = exp (12.2(8) - 16800(600)/T) (Torr/Torr-1/g)/sup 2/) respectively, where K is defined implicitly by P = Kq/sup 2/ with P the equilibrium pressre (in Torr) and q the bulk concentration (in Torr-l/g). These values, in conjunction with a model for the solubility, predict that the constant for tritium, K/sub T/ approx. 4 K/sub H/. Consequently, the regeneration of tritium will be faster by a factor of four over that for hydrogen at the same temperature, or the tritium regeneration temperature can be reduced approx. 50/sup 0/K compared to hydrogen for the same regeneration time

Measurements of the hydrogenic recombination coefficient for the TFTR vacuum vessel

Characteristic values of the recombination rate coefficient for hydrogen and deuterium in stainless steel have been measured for the inner wall of the TFTR vacuum vessel for vessel temperatures of 25 to 100 C. In situ measurements of k/sub r/ are important for predicting the hydrogen isotope retention in the wall as a function of time, temperature, and discharge exposure, particularly because existing laboratory measurements of k/sub r/ for stainless steel span a range of four orders of magnitude. The measurement technique involved the observation of the decrease in hydrogen pressure during a glow discharge in the TFTR vacuum vessel with an initial static gas fill. The resulting values of k/sub r/ at 25 C are in the range of (0.4 to 4) x 10/sup -27/cm/sup 4/-s/sup -1/ assuming a value of the hydrogenic diffusivity of 2 x 10/sup -12/cm/sup 2/-s/sup -1/ at room temperature. No significant isotopic dependence was observed and the temperature dependence of k/sub r/ is consistent with the literature value (0.5 eV) of the activation energy. The implications of this range of values of k/sub r/, for the estimation of the in-vessel tritium inventory following D-T operation in TFTR are discussed

Controlling the optical properties of Gallium nanoparticles with a beam of electrons

For the first time, we show that a beam of electrons can change the optical properties of a nanoparticle film through the mechanism of controlling the structural phase coexistence in the nanoparticles. This study is motivated by a desire to understand the exciting physics of phase equilibria in metallic nanoparticles and clusters, and is stimulated by interest in the properties of metallic nanoparticles relating to their potential role in future highly integrated photonic devices, as the active elements of waveguiding and switching structures addressed by an electron beam

Nanoscale light-induced phase transformation in alpha-gallium as the source of a broadband optical nonlinearity

Summary form only given. Using a tunable optical parametric oscillator we discovered that the interface between gallium and silica displays an exceptionally broadband nonlinearity. At temperatures several degrees below gallium's melting point (~30°C) the reflectivity increases by up to 40% in response to 3 ns excitation pulses at wavelengths from 440 to 700 nm. It is shown how the reflectivity change depends on the excitation fluence, and that it saturates at about 6 mJ/cm

Collisional Excitation Transfer Between Rb(5P) States in 50-3000 Torr of He-4

Measurements of the mixing rates and cross sections for collisional excitation transfer between the 5P(1/2) and 5P(3/2) states of rubidium (Rb) in the presence of He-4 buffer gas are presented. Selected pulses from a high repetition rate, mode-locked femtosecond laser are used to excite either Rb state with the fluorescence due to collisional excitation transfer observed by time-correlated single-photon counting. The time dependence of this fluorescence is fitted to the solution of rate equations which include the mixing rate, atomic lifetimes and any quenching processes. The variation in the mixing rate over a large range of buffer gas densities allows the determination of both the binary collisional transfer cross section and a three-body collisional transfer rate. We do not observe any collisional quenching effects at He-4 pressures up to 6 atm and discuss in detail other systematic effects considered in the experiment

Gigantic broadband optical nonlinearity in gallium films deposited by ultrafast laser ablation

Gallium-Silica interfaces have emerged as a new type of structure that combines a strong nonlinearity [1] with picosend switching-on time [2]. Here we report that the optical nonlinearity of gallium films deposited on fused silica by ultrafast pulsed laser ablation is very broadband, spanning from 480 nm to 810 nm

Power transport to the PDX scoop limiter

Power transport to the PDX graphite scoop limiter was measured during both ohmic- and neutral-beam-heated discharges by observing its front face temperatures using an infrared camera. Measurements were made as a function of plasma density, current, position, fueling mode, and heating power for both co- and counter-neutral beam injection. The measured thermal load on the scoop limiter was 25 to 50% of the total plasma heating power. The measured peak front face midplane temperature was 1500/sup 0/C corresponding to a peak surface power density of 3 kW/cm/sup 2/. This power density implies an effective parallel power flow of 54 kW/cm/sup 2/ in agreement with the radial power distribution extrapolated from TVTS and calorimetry measurements. Symmetric and asymmetric thermal loads were observed. The asymmetric heat loads were predominantly skewed toward the respective ion drift directions for both co- and counter-injected beams. The results of transport calculations are consistent with the direction and magnitude of the observed asymmetries