We performed an axi-symmetric, two-dimensional experiment on the high-explosive LX-14. We used low-energy X-rays to image the detonation front at multiple times. The experiment provides a stringent test of radiographic unfolding techniques and has the potential to provide high-pressure data on the equation of state of the explosive. (C) 1999 Elsevier Science B.V. All rights reserved.

The spectrum of neonlike gold (+69) is observed in a beam-foil light source utilizing an x-ray crystal spectrograph. Precision wavelength determinations indicate variations from multi- configurational Dirac-Fock calculations for states sampling the 2s hole states consistent with previous observations in bismuth (+73).

A low-energy beam line facility for atomic and surface physics research has been added to the injection line of the ECR source at the LBL 88 in. cyclotron. Beams throughout the periodic table can be delivered to three beam line stations at energies up to 15QkeV. Experiments using this facility include forbidden line emission from the ion beam, ion-atom collisions, merged electron-ion beams and sputtering by highly charged ions.

The n = 2 to n = 4 Balmer-..beta.. transitions in hydrogenic Fe/sup 25+/ have been observed in the first order of Bragg diffraction in a beam-foil light source. Simultaneous observation of the 1s-2p Lyman-..cap alpha.. transitions from the same source in the fourth diffraction order leads to a new method for the measurement of the 1s ground-state Lamb shift which is less sensitive to uncertainties arising from Doppler shifts than previous work. With the use of the Balmer-..beta.. transitions for calibration, the Lyman-..cap alpha.. wavelengths are for the 1s /sup 2/S/sub 1/2/--2p /sup 2/P/sub 3/2/ transition, 1.77815 +- 0.00019 A, and for the 1s /sup 2/S/sub 1/2/--2p /sup 2/P/sub 1/2/ transition, 1.78364 +- 0.00019 A. Values of the Lamb-shift contributions to the 1s-2p transitions, and the 2p/sub 1/2,3/2/ fine structure, are extracted.

The spectroscopy of very highly ionized atoms provides an important testing ground for multielectron atomic theory. We report preliminary experimental results on the n = 3 → 2 spectra of Bi73+ and Au69+ obtained at the GSI UNILAC accelerator.

The spectra of argon ions emitted from a plasma created by discharging a 3-TW relativistic electron beam generator through an argon gas column are reported. New lines have been classified for 2s 2pn–2pn+1 transition arrays in Ar XI–XV and energy levels have been derived for lithiumlike argon XVI. The effects of mass motion Doppler shifts on the spectra have been measured and systematic shifts of transition energies with charge state are observed in the data.

The $n=2$ to $n=4$ Balmer-$\ensuremath{\beta}$ transitions in hydrogenic ${\mathrm{Fe}}^{25+}$ have been observed in the first order of Bragg diffraction in a beam-foil light source. Simultaneous observation of the $1s\ensuremath{-}2p$ Lyman-$\ensuremath{\alpha}$ transitions from the same source in the fourth diffraction order leads to a new method for the measurement of the $1s$ ground-state Lamb shift which is less sensitive to uncertainties arising from Doppler shifts than previous work. With the use of the Balmer-$\ensuremath{\beta}$ transitions for calibration, the Lyman-$\ensuremath{\alpha}$ wavelengths are, for the $1s^{2}S_{\frac{1}{2}}\ensuremath{-}2p^{2}P_{\frac{3}{2}}$ transition, 1.778 15\ifmmode\pm\else\textpm\fi{}0.000 19 \AA{}, and for the $1s^{2}S_{\frac{1}{2}}\ensuremath{-}2p^{2}P_{\frac{1}{2}}$ transition, 1.783 64\ifmmode\pm\else\textpm\fi{}0.000 19 \AA{}. Values of the Lamb-shift contributions to the $1s\ensuremath{-}2p$ transitions, and the $2{p}_{\frac{1}{2},\frac{3}{2}}$ fine structure, are extracted.

The spectroscopy of very highly ionized atoms provides an important testing ground for multi-electron atomic theory. We report preliminary experimental results on the n = 3 ..-->.. 2 spectra of Bi/sup +73/ and A/sup +69/ obtained at the GSI UNILAC accelerator. 19 refs., 4 figs.

During this past year, neon-like krypton plasmas have been studied on the Defense Nuclear Agency PITHON generator operating as a collisionally pumped x-ray laser system. This report describes improvements made in plasma formation, simultaneity, and linearity, spatially resolved measurements of the plasma electron temperature and density, and progress made in the line identification of highly ionized krypton lines in the XUV region where the lasing lines are predicted to occur. Also, the appendices describe the large x-ray diagnostic setup for these experiments and the theory and method of predicted x-ray laser transitions and the small signal gains expected in the inverted transitions.