[en] In FY82 we have completed the calculation of the collision strengths, excitation rate coefficients, level populations and spontaneous decay rates for the configurations 2s²2p/sup k/, 2s2p/sup k+1/ and 2p/sup k + 2/ and for the ions with atomic numbers 20 less than or equal to Z less than or equal to 36. Complete sets of atomic data for these elements are provided in the paper Forbidden Line Emission from Highly Ionized Atoms in Tokamak Plasmas, which appeared in the December 1982 issue of Journal of Applied Physics. No data are presented here

[en] A high resolution grazing incidence spectrograph, provided by the Naval Research Laboratory and the Goddard Space Flight Center, has been installed on the Omega laser facility of the Laboratory for Laser Energetics (LLE) at the University of Rochester. This 3 meter instrument, with a 1200 lines/mm grating blazed at 2⁰ 35', has produced extremely high quality spectra in the wavelength region 10 A to 100 A. Spectra have been obtained from glass microballoon targets that are coated with a variety of high-Z materials. Transitions from the Na-like and Ne-like ionization stages of Fe, Ni, Cu, and Kr have been identified

[en] This report discusses the following topics: Atomic data and line intensities; analysis of PLT spectra; zeeman splitting of magnetic dipole transitions; and level populations in dense plasmas

[en] Two different Monte Carlo methods have been developed for benchmark computations of small-sample-worths in simplified geometries. The first is basically a standard Monte Carlo perturbation method in which neutrons are steered towards the sample by roulette and splitting. One finds, however, that two variance reduction methods are required to make this sort of perturbation calculation feasible. First, neutrons that have passed through the sample must be exempted from roulette. Second, neutrons must be forced to undergo scattering collisions in the sample. Even when such methods are invoked, however, it is still necessary to exaggerate the volume fraction of the sample by drastically reducing the size of the core. The benchmark calculations are then used to test more approximate methods, and not directly to analyze experiments. In the second method the flux at the surface of the sample is assumed to be known. Neutrons entering the sample are drawn from this known flux and tracking by Monte Carlo. The effect of the sample or the fission rate is then inferred from the histories of these neutrons. The characteristics of both of these methods are explored empirically

[en] Spectra between 1200 and 1560 A of a supergranulation cell interior and cell boundary observed near Sun center are discussed. Absolute intensities are given for selected lines of chromospheric and transition-zone ions. The spectra were obtained by the NRL normal-incidence spectrograph on Skylab. The spectral resolution is 0.06 A, and the spatial resolution is 2'' x 60''. The width of the cell boundary was found to be approx.10'' in lines of low-temperature ions such as C II and O I, and approx.6'' in lines of high-temperature ions such as C IV and N V. The brightness contrast between cell interior and boundary is an increasing functions of the characteristic emitting temperature of the observed lines between approx.8 x 10³ K and approx.1.3 x 10⁵ K. The maximum contrast is observed in O IV and is about a factor of 5. Above and below the temperature of O cV the contrast falls, and is about 1.5 for lines of O I and S I. The full widths at half-maximum (FWHM) of the optically thin lines are the same over cell interiors and cell boundaries, and agree with the widths observed in limb spectra. From the FWHM of the 1207 A Si III line, optical depths at line center of 5.8 and 1.6 are deduced for the cell boundary and cell interior, respectively. The electron density in the cell boundary appears to be nearly equal to the cell interior density. From the intensities of the intersystem lines of O IV (2s²2p ²P/sub J/⁰-2s2p²⁴P/sub J//sub prime/) measured above the limb in the quiet Sun, an electron density of 4.6 x 10⁹ cm^-3 is derived for the O IV emitting region. This density does not change within the first 8000 km above the limb, and is about a factor of 1.6 lower in the north polar coronal hole. Assuming a constant pressure, the characteristic height of the Si III emitting region is approx.840 km in the boundary and approx.380 km in the cell interior. The results are compared with a recent model by Gabriel

No abstract available

[en] X-ray spectra of highly ionized elements are widely used in diagnosing high temperature plasmas from astrophysical as well as from laboratory sources. The emission lines in the X-ray region are produced primarily from two different types of transitions. One type involves the transitions 1s-2p in hydrogen-like ions, helium-like ions and their associated satellites. The second type involves the transitions 2 l - n l ' for n > 2. These transitions are sensitive to electron temperature, electron density and the ionization balance. High quality spectrometers in the X-ray region have instrumental line widths that in many cases are significantly less than the true line widths. As a result, it is quite convenient to use the physical information in the line profiles to determine additional properties of the plasma under investigation. In this paper results from recent experiments concerning solar plasmas as well as laboratory sources are described. 13 references, 13 figures

[en] Spectra of highly ionized Ge, Kr and Mo in the spectral region of 10 to 80A were excited in laser-produced plasmas. The plasma was obtained by focusing the energy of the 24 laser beams of the University of Rochester Omega system on 0.4 mm diameter microballoon targets. The laser pulse duration was in the range of 0.87 to 1.09 ns, with total energy in the range of 1.8 to 2.2 kJ. The observed spectral lines include n = 2-2 transitions in the oxygen and fluorine isoelectronic sequences and n = 3 to 4 transitions in the sodium, magnesium and aluminum isoelectronic sequences. The present observations are compared with previous experimental and theoretical studies

[en] A model is developed which is capable of describing the evolution of gain resulting from both rapid radiative and expansion cooling of a recombining, freely expanding plasma. It is demonstrated for the particular case of a carbon/selenium plasma that the cooling rate which leads to optimal gain can be achieved by adjusting the admixture of an efficiently radiating material (selenium) in the gain medium (carbon). Comparison is made to a recent observation of gain in a recent NRL/Rochester experiment with carbon/selenium plasma for the n = 3 → 2 transition in C VI occurring at 182 A. The predicted maximum gain is approx.10 cm^-1, as compared to observation of 2 to 3 cm^-1

[en] A discussion of laboratory spectra similar in temperatures and ion abundances to solar flare spectra is given. The laboratory spectra were obtained from high temperature plasmas produced by high power lasers and low inductance vacuum sparks. The current state of knowledge regarding line identifications in laboratory spectra is reviewed, and some of the results are used to identify lines in the high temperature solar flare spectrum in the 100 A region and in the 1000 A region. In addition, the physical dimensions and temperatures of the hot regions in the plasmas produced by the low inductance spark were recently measured, and a short summary of the results is given. (Auth.)