For inverse scattering theories, it is well known that in order to guarrantee the existence and uniquness of the solution, drastic restrictions must be imposed on the scattering potential or on the scattering data collected from experiments (see for example Newton 1966). The existing theories in their original form such as the Geldfan Levitan or the Marehenko equations therefore cannot be used in a straightforward manner and some further steps toward simplifications have to be considered.

In inelastic scattering problems where many coupled channels must be taken into account to construct various elements of the scattering matrix the problem become much more complicated both from the theoretical and experimental point of view. The present work deal only with the energy fixed case and show that a solution can nevertheless be obtained by using on one hand the conventional technique of the Abelian transformation which has been extensively applied in the JWKB approach to the one channel problem (see for example a general review by Buck 1971) with on the other some results obtained recently concerning a system of coupled differential equations (Cao 1982 1).

The Helium-like-resonance intercombination and forbidden lines (ls21S−ls2p 1P, ls21S−ls2s 3P, ls21S−ls2s 3S respectively) can be observed from hot, low density plasmas such as coronal or tokamak plasmas. They can be used either to measure the electron temperature from the ratio of their intensity to that of the corresponding satellite lines (1s2nℓ′ − ls2ℓnℓ′) as described by Gabriel (1972) or directly as a density diagnostic (Gabriel and Jordan, 1972). The soft X-ray spectra obtained from these plasmas have been observed from space satellite experiments such as the Solar Maximum Mission (Acton et al., 1980), Hinotori (Tanaka et al., 1982) and P78–1 (Doschek et al., 1982) or from tokamaks such as PDX, PLT (Princeton, USA), TFR (Fontenay-aux-Roses, France). The analysis of some of these spectra, for example, Mg XI (Faucher et al., 1983), Ti XXI (Bely-Dubau et al., 1982b) and Ca XIX (Bely-Dubau et al., 1982a, Jordan and Veck 1982) show that these diagnostics are sensitive to the accuracy of the atomic data.and demonstrate the need for improved calculations of the excitation rates for the He-like ions.

Experimental studies of the intensity of the (2pl/2-lsl/2) and (2p3/2-lsl/2) lines of SXVI in the Alcator Takamak show large departures from the statistical ratio of 0.5 (Källne et al. 1982). Similar enhancements in the intensity ratio have been reported in solar observations (Grineva et al. 1973, Phillips et al. 1982) for the Mg XII lines and in laser produced plasmas (Boiko et al. 1977). Theoretical calculations of the intensity ratio have been carried out by Vinogradov et al. (1977), Beigman et al. (1979) and Ljepojevic et al. (1984) . We suspect that proton-impact induced transitions play a crucial role which depends sensitively on the conditions of temperature and density in the Plasma. In this abstract we will present some preliminary results of proton-impact excitation cross section calculations, for the n=2 sub levels of hydrogenic ions.

The charge state distribution of multiply charged Ar ions in an electron cyclotron resonance (ECR) heated microwave discharge (Bernhardi et al. 1976) was measured by means of VUV-spectroscopy in the wavelength region λ ≤ 100 nm (Marlinghaus 1984). Ion densities were computed from absolute line intensities in a modified corona model. Assuming electron impact excitation of groundstate ions to play the major role and neglecting all other processes leading to excitation, the ion density nz is given by

We have been publishing new compilations of energy levels for single elements in all stages of ionization as each is completed. Those now in print in the Journal of Physical and Chemical Reference Data are helium (1973), sodium (1981), magnesium (1980), aluminum (1979), silicon (1983), potassium (1979), calcium (1979), scandium (1980), titanium (1979), vanadium (1978), chromium (1977), manganese (1977), iron (1982), cobalt (1981) and nickel (1981). A volume containing atomic energy levels of all rare earth elements was issued in 1978. We have now updated our compilations for the iron period (K through Ni, 235 spectra), which will be published in a single volume.

The NBS Data Center on Atomic Transition Probabilities is nearing completion of a critical compilation of atomic transition probability data on allowed and forbidden transitions in the elements scandium through nickel in all stages of ionization. This compilation constitutes a revision of a series of smaller NBS compilations published in recent years in the Journal of Physical and Chemical Reference Data. Upon completion of this project, work on updating of an even earlier compilation covering the elements hydrogen through neon will be initiated.

The world literature on atomic transition probabilities is collected and catalogued on an ongoing basis by the Data Center. A master reference list is maintained, and annotated bibliographies are issued as the number of new articles in the literature and the resources of the Center permit. A computerized bibliographic database system is being developed to enhance the capability for handling bibliographical information in the NBS data centers on transition probabilities, line shapes and shifts, and energy levels. Development of a computerized database of critically evaluated numerical data on atomic spectroscopic quantities is planned for the future.

Laser produced plasmas have been shown to be excellent sources for applications in the XUV and soft X-ray spectral region. We are using a 550 mj, 25 ns (FWHM) ND:YAG laser operating at a repetition rate of 10 Hz to produce plasmas above rotatable solid targets. The focal spot of the laser beam with a 31 cm lens was measured to be 170 μm (approximately twice the diffraction limit), using a diode array having a 170 μm resolution. Broadband output in the soft X-ray region was studied using a windowless PIN photodiode with an A1203 surface covered with a polyethylene filter with transmission between 44 Å and 120 Å. Results are presented for the source’s soft X-ray intensity for several elements as a function of laser energy, focus and driving wavelength, as are preliminary results using the source for high resolution spectroscopy and for soft X-ray lithography.

The interaction of an intense short-wavelength laser beam with a solid foil target is a topic which has been studied vigorously for many years. Many inherent problems still exist, however, in our understanding of observed experimental data. In particular, the problem of transport through the target material of the deposited laser energy continues to be the focus of many investigations. Although most.of the work has been dominated by particle transport phenomena, it was shown in a previous paper that radiation processes and photon transport often play a major role in the redistribution of the deposited energy in laser driven plasmas. In this presentation, we continue our investigation of the role of atomic physics and radiative emission in laser-produced plasmas by studying the effects of these physical processes as a function of varying initial conditions for both aluminum and carbon foil targets.

X-ray spectra of highly ionized atoms (Tm to Pt) emitted from Laser produced plasma are characterized by the simple structure given by resonant transitions of the Nil-like ions, accompanied by the more complex pattern of satellite transitions emitted by ions in the neighbouring states of ionization. An analysis of these structures has been given recently for the satellites of the 3d10 − 3d94p[l] and of the 3p63dl0 − 3p53d104s, 4d[2] transitions of the Nil-like inns. However, most of the radiation emitted in this spectral range [4–10Å] concentrate in a wide, rather structureless satellite feature in the long wavelength side of the 3d10 −3d94f Ni-I like transition, on which some lines are superimposed. Line identification has been achieved successfully with the methods of [1], [2] and will be published separately. In this communication, we deal only with the pseudocontinuum.

We report the results of X-ray emission measurements made at various plasma locations in the Tandem Mirror Experiment-Upgrade (TMX-U). By manipulating the electron and ion density profiles within the magnetic mirror end cells, a local minimum in the axial electrostatic potential creates a barrier that thermally isolates central cell electrons from those in the end cells. This thermal barrier makes it possible to heat end cell electrons to a temperature (~1.6 keV) that is significantly higher than the central cell value (30 to 200 eV), thereby increasing the ion confining potential. Formation of this potential peak is attributable, in part, to mirror-trapped hot ions (8 keV) that are injected as beams of neutral particles. The resulting ion density profile exhibits two symmetric peaks at the locations of the ion turning points and a depression where the magnetic field is a minimum. Electron cyclotron resonance heating (ECRH) is applied at the density minimum and produces a population of hot, mirror-trapped electrons (20 to 200 keV). It reduces an already depressed electrostatic potential to establish the thermal barrier. In addition, ECRH applied at the outer density peak raises the -ion confining potential and enhances central cell ion confinement by increasing the end cell electron temperature. X-ray measurements are made with solid state and scintillation detectors at the ECRH locations. Medium resolution spectra are obtained over a broad energy band and have proven to be an important tool for determining the efficiency of thermal barrier formation. We present our initial findings from these non-Maxwellian plasmas.

The MINIMAFIOS ECR source at Grenoble has recently produced stable beams of highly charged Al. We have studied electron capture into excited states for Al8+ ions extracted at 10 kV colliding with an H2 molecular target under single collision conditions. Using a grazing incidence spectrometer covering the region 250 Å to 1100 Å, we have made a relative intensity measurement of the radiative decay from excited (nl) states of Al7+ following the charge exchange collision. The Al7+ spectra show known transitions from the ls22s2p3 excited state. We discuss the presence of the ls22s2p2(4P) metastable state in the incidence Al8+ beam. The spectra also show many transitions which up to now are unidentified, in particular transitions for the wavelength region between 300 and 400Å and that between 600 and 700Å. To identify the transitions, we compare our spectrum with preliminary theoretical wavelengths calculated using the multiconfiguration Dirac-Fock method including transitions from n = 3, 4 and 5. These preliminary results reveal transitions from n = 5 to 4 for the observed spectra in the 600Å region and transitions from n = 4 to 3 for the observed spectra in the 300Å region.

The present model is the time-dependent version of a previous model (Sureau et al. 1983) in which the population distribution was assumed in steady state. A finite set of levels is partitioned in four subsets: the Z-ion ground-level and, contingently, the first near-degenerated levels (subset 1); all the successive excited Z-ion levels up to n=5 (subset 2); a finite number of higher Rydberg levels (because of the limitation of the series in the plasmas) which are assumed in LTE with the Z+l−ion ground-level (subset 3, called the thermal band); and the Z+l ion ground-level (subset 4).

The physical processes explicitly considered are the radiative cascades and the transitions between the Z-ion bound levels induced by electron-ion collisions. The radiative-transition probabilities are given by ab-initio calculations using a modified Hartree-Fock method including the spin-orbit interaction (Sureau et al., 1984). The collision rates are derived by the Van Regemorter formula multiplied by an adjustable parameter Fc.

We report here the observation of spectral lines in the F I, 0 I, N I, and C I isoelectronic sequences of Cu, Zn, Ga, Ge, As, Se, Br, and Rb. The plasma was produced by the spherical irradiation of solid targets using six frequency-tripled beams from the OMEGA laser system at the University of Rochester. The wavelengths were recorded using a 3 meter grazing incidence spectrograph, and the wavelengths were determined relative to several previously observed lines in the F I, 0 I, and Na I sequences. There is good overall consistency with the wavelengths recommended by Edlen (1983) for the F I and O I sequences and with the wavelengths measured by Kononov (1979) for the Na I sequence. Most of the observed transitions in the N I and C I sequences represent new identifications, and a complete set of energies for the 2s2p4 configuration of the N-like ions Cu XXIII, Zn XXIV, Ga XXV, and Ge XXVI is presented.

Laser-produced plasmas have some of the highest temperatures and densities obtainable in the laboratory. This offers the opportunity to perform spectroscopic studies in new temperature and density regimes under controlled laboratory conditions. Temperatures can range from greater than 1 keV to less than 1 eV, while densities range from less than 1020e−/cm3 to greater than 1023e−/cm3. X-ray spectroscopy has been an important tool in diagnosing these large ranges of temperature and density. Relative line intensities of resonance and satellite lines can be used to diagnose the lower densities and higher temperatures. (Galanti and Peacock 1975, Boilo et al. 1979) For the denser plasmas Stark broadening is a good density diagnostic. (Yaakobi et al. 1977) Absorption spectroscopy measuring edge shifts had recently been used to probe the low temperature, high density region. These plasmas, with their high-energy density, are transient with total time scales ranging from 100 psec to greater than 1 nsec, depending on the laser driver pulse. In order to make detailed measurements from these plasmas, sensitive, time-resolved spectrographs have been developed. (Lewis et al. 1980, Kauffman et al. 1983) These spectrographs can measure time histories of spectral lines with resolving powers of 300 or greater and with time-resolutions of 20 psec. By using such instruments, studies of the dynamics of the plasma can be made.

In a conventional laser operating in the near ultra-violet, optical or infra-red spectral bands the photon energies, not exceeding lOeV, are closely matched to the electronic or molecular energy levels of neutral and weakly ionised atoms. Consequently typical photon energies (~ eV), and transition lifetimes (~ ns) closely match the characteristics of fast electrical circuitry feeding a weakly ionised discharge which may be used to pump either directly or indirectly the laser medium.

In a X-ray laser operating at about 10Å, photon energies are about 1 keV, and lifetimes about 10−14s (l0fs). In consequence the power required to pump the laser must be expected to increase rapidly as the wavelength decreases. The gain per unit length is given by:

where ζ is the line shape factor, A the spontaneous transition probability, λ the wavelength, and Δν the width of the line, and (n2,g2) and (n3,g3) the population density and statistical weight of the lower and upper laser states respectively. The total power loss per unit area, p, of the medium must exceed that emitted by spontaneous decay of the laser transition.

The spectra of highly ionized scandium, titanium, vanadium and chromium emitted from laser-produced plasmas have been recorded in the region 270–600 Å. The radiation from a Quantel NG24 Nd:YAG/glass laser giving the maximum energy 4J in 3ns pulses was focused on plane metal targets. The target was placed at the Sirk’s focus of a 3-m normal incidence spectrograph with the target surface parallel to the slit. The laser beam was perpendicular to the target and to the entrance axis of the spectrograph. By this arrangement the spectral lines from different ionization stages differ in length, the highest states giving the shortest lines. Well-determined lines from spark recordings of sodium-, magnesium-, aluminium-, and silicon-like ions were used for the wavelength determinations.

Spectral line profiles, broadened mostly by Stark effects from electric fields produced by charge particles, and diélectronic satellite line intensities have recently been used for determining electron densities in the dense region of laser-created plasmas. We present here a direct comparison of electron density measurements in the conduction region of laser created plasmas on a plane target using these two techniques.

Experiments were carried at the GRECO laser facility, using the Nd phosphate glass laser at its second harmonic (0.53 μm) and 600 ps pulse length. The laser was focused on a 160 μm focal spot in which was centered a 25 or 50 μm diameter aluminum dot implanted on a carbon substrate. Laser intensities were in the range 1 × 1014−3 × 1014 W/cm2. The ls4p−ls2 He-like transition, the 4p−ls H-like transition and the Ly c satellites were recorded on the same spectrum with a PET flat crystal spectrograph. Spot spectroscopy provided quasi-homogeneity and low reabsorption along the line of sight which was tilted 7° out the target surface. 3 μm resolution along the laser axis was obtained with an imaging knife-edge placed 1 mm apart from the target.

The dielectronic satellite lines from the ls21a 3lb and ls31a 31b, double-excited configurations of lithium-like ions have been studied experimentally and theoretically under dense-plasma conditions. Good agreement between theory and measurements performed in laser-target interactions at 0.53 m wavelength, 1014 W/cm2 laser irradiance show that collisional equilibrium conditions are reached between n − 3 singly and double excited levels at electron densities greater than 1022 cm−3 in Al and Si.

Recently, a novel technique known as spot spectroscopy has been developed for use in diagnosis of laser-produced plasmas. This method involves the implantation of tracer microdots (circular or rectangular) of material in laser targets whose composition and size (typically about 100 μm) are known. Aluminum has been a popular choice since its K-shell lines are readily produced; however, any element appropriate to the experiment may be chosen. A major advantage of this technique is that the plasma produced from each microdot is generally homogeneous in the direction parallel to the plane of the original target. Since the dots can be distinguished spectroscopically, the diagnosis of each spot is not subject to the ambiguities created by the presence of gradients. Gradients do exist in each blowoff tracer perpendicular to the target plane; however, it is possible to resolve spatially the cylindrical blowoff created by each dot with appropriate orientation of the spectrograph slit.

We have used the method of two laser produced plasmas (Jannitti et al. 1984a) to measure the absorption spectra of the ions Be++ (Jannitti et al. 1984b), Be+ (Jannitti et al. 1984c) and B+ in the grazing incidence and normal incidence region. Both discrete and continua transitions have been measured and values of the photoionization cross sections are derived.

The experimental set up referring to the normal incidence investigation is shown in Fig. 1. A laser beam of 10 J of energy and 15 ns (FWHM) duration is split in two parts and generates two plasmas: one on target T of high atomic number (Cu) used as a background continuum emitting source and a second on target A for producing the absorbing species to be studied. For the latter a sphero-cylindrical lens is used producing a focal spot 100 µm wide and up to 10 mm long. The continuum radiation produced on a target tilted 45° both with respect to the laser beam and to the axis of observation was collected by a toroidal mirror whose radii of curvature, R = 640 mm in the plane of incidence and ρ = 530 mm in the plane perpendicular to the former are such to compensate the astigmatism of the 2 m radius grating.