The measured line profiles of the Siiv 3s S-3p P doublet during 10-T operation on the Alcator-C tokamak show evidence of a contribution due to the Zeeman efFect to these profiles.The assumption that these line profiles are single lines broadened only by instrumental efFects and thermal broadening yields apparent kinetic temperatures for the two lines which difFer by approximately 50%. Neither of the resulting temperatures is reasonable for Sirv under typical Alcator operating conditions and the difFerence between the temperatures cannot be explained by Doppler efFects. Modifying the nonlinear least-squares fitting routine to include the {unresolved) components predicted by the weak-field limit of the Zeeman efFect yields kinetic temperatures for these lines which are in agreement and are reasonable for the region of the plasma in which Si tv exists.Finally, a study of the Zeeman efFect in 0vu shows that contributions from this process are important in determining ion temperatures from line broadening of the 0vu 2s 'Sl -2p I'& emission line in the vuv spectrum from Alcator-C plasmas.

We report on the performance of high x-ray fluence Kr K-shell sources that are being developed for high energy density experiments. These targets are 4.1 mm in diameter 4.4 mm tall hollow epoxy tubes having a 40 μm thick wall holding 1.5 atm of Kr gas. For these shots, the National Ignition Facility laser delivered a nominally constant total energy of ≈750 kJ of 351 nm (3ω) light at the three power levels [e.g., ≈120 (low), ≈145 (medium), and ≈210 TW (high)]. The Kr K-shell (Ephoton = 8–20 keV) x-ray radiant intensity and radiant energy (kJ/sr) of these sources were found to increase as a function of laser power but began to plateau at the highest laser power. The Kr K-shell radiant energy increased from ≈1 kJ/sr at ≈120 TW to ≈2 kJ/sr at ≈210 TW. Radiation hydrodynamics simulations predict radiant energies to be always higher than these measurements. The increase in K-shell emission is attributed to its strong dependence on the electron temperature. Electron temperature distributions were inferred from measured Heα and Lyα line emission through the use of a genetic algorithm and Scram modeling. The inferred temperatures from the experiment are 20% to 30% higher than those predicted from modeling.

Laser heated plasmas have provided recently some of the most powerful and energetic nanosecond length laboratory sources of x-ray photons (Ephoton = 1–30 keV). The highest x-ray to laser conversion is currently accessible by using underdense (ne ∼ 0.25 nc) plasmas since optimal laser coupling is obtained in millimeter scale targets. The targets can have conversion efficiencies of up to 10%. Several types of targets can be used to produce underdense plasmas: metal lined cylindrical cavities, gas pipes, and most recently nano-wire foams. Both the experimental and simulation details of these high intensity x-ray sources are discussed.

This paper describes the design, construction, and performance of a single-stage microchannel-plate image intensifier used as a photon counting detector over the wavelength range from 1150 to ∼2000 Å. The intensifer incorporates three high strip current (∼300 μA) microchannel plates, constructed with 12-μ-diam channels and 15-μ center–center spacing, in a ‘‘Z’’ configuration. The use of high strip current MCPs requires gating the power supply to protect the plates from thermal runaway of the strip current. The output pulses are proximity focused onto a P-46 phosphor screen, which is fiber-optically coupled to a linear, self-scanning photodiode array. Maximum frame rates for the photodiode array are ∼ 125 000 frames/s, with maximum count rates of ∼25 000 photoevents/s. The detector was placed at the focal plane of a 1-m focal length Ebert–Fastie spectrometer and the performance characteristics of the spectrometer-detector system were evaluated using a hollow cathode Pt lamp. The linewidths measured during this evaluation demonstrate that the spatial resolution of the detector is better than 50 μ. The spectrometer-detector system was then used to determine ion temperatures from Doppler broadened impurity lines emitted from plasmas of the Alcator C tokamak. This detector demonstrated more than an order of magnitude increase in sensitivity compared to a photon-counting photomultiplier tube with a vibrating mirror previously used for these measurements with the same spectrometer. This permitted a determination of the central ion temperature of the Alcator C tokamak using the ‘‘forbidden’’ line of Fe xii at 1354.1 Å which was not detected with the previous system.

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