Ionization of highly charged relativistic ions by neutral atoms and ions

Ionization of highly charged relativistic ions by neutral atoms and ions is considered. Numerical results of recently developed computer codes based on the relativistic Born and the equivalent-photon approximations are presented. The ionization of the outer shells dominate. For the outer projectile electron shells, which give the main contribution to the process, the non-relativistic Schr\"odinger wave functions can be used. The formulae for the non-relativistic reduction of the Dirac matrix-elements are obtained for ionization of electrons with arbitrary quantum numbers $n$ and $\ell$.Comment: 7 pages, 3 figure

Electron impact ionization of Kr XI-Kr XIX ions

Cross sections for the single ionization of Kr XI-XIX ions by electron impact are calculated in the Coulomb-Born approximation by the code 'ATOM' and compared with experimental data and other theoretical results for Kr XI, Kr XII and Kr XIX. Single electron impact ionization is the sum of the contributions from direct ionization and from excitation of the autoionizing levels. The first part includes only ionization from the 3s, 3p and 3d shells since ionization from the 1s, 2s, 2p shells results in double ionization. The autoionizing levels (1s(2)2s2p(6)3s(2)3p(6)3d(m)nl and 1s(2)2s(2)2p(5)3s(2)3p(6)3d(m)nl) decay via autoionization and finally contribute to single ionization. The results are found to be in satisfactory agreement with the experimental results obtained in a crossed electron-ion beam experiment in the energy range from threshold to about 6 keV. The case of ions formed in metastable states is studied as they were observed experimentally

Spectra of OII in the plasma boundary of TEXTOR-94

Spectra of the 011 ion were obtained with temporal and spatial (along the poloidal radius) resolution by injecting of oxygen-containing molecules through a block of the upper poloidal limiter of TEXTOR-94 into the boundary plasma. Three different wavelength regions (4660+/-100,4340+/-100, 3730+/-100 Angstrom) were observed during reproducible TEXTOR-94 discharges with n(e) = 1 x 10(18) m(-3), T-e = 90 eV at the last closed flux surface (LCFS). For calibration purposes the oxygen emission was simultaneously registered in all discharges with a 2D camera using the light from an O 11 line at 4416 Angstrom. Radial intensity distributions of lines corresponding to the transitions 2p(2)[P-3]3s-2p(2)[3P]3p (components of the multiplets P-4-S-4, P-4-P-4 P-4-D-4, P-2-D-2 and 2p(2)[D-1]3s-2p(2)[D-1]3p (doublet D-2-D-2) were measured. It is shown that the relative intensities of the lines inside the multiplets are in good agreement with theoretical data calculated in SL-coupling. An appropriate collisional-radiative model (the level list and the corresponding atomic database) has been developed and calculations have been carried out using the GKU kinetic code developed at the P.N. Lebedev Institute. Cross-sections of atomic processes have been calculated using the ATOM code by the K-matrix method. A comparison of theoretical and experimental data is presented. It is shown that the relative multiplet intensities have a weak dependence on electron density and temperature. The populations of the ground configuration states of O II were investigated. Absolute values for the 'ionization per photon' were measured and a comparison with modelled values is given

Close coupling approach for heavy particle collisions with an excited atom: transitions between n = 3 states in He

The close coupling (CC) equations in the impact parameter (IP) representation are considered. Calculations for transitions in the 3s-3p-3d He atom system induced by collisions with single charged ions were carried out. Results are compared with those obtained in the frame of the Born approach. The effects of stepped transitions, normalization, channel coupling and their dependence on interaction strength are discussed

Tungsten spectrocopy for the measurement of W-fluxes from plasma facing components

Tungsten is foreseen for a full W-divertor of JET where tungsten will totally replace carbon as the material for the target plate. Also ITER operation is planned to be carried out with tungsten as one of the first wall materials, e.g. in the upper regions of the lower divertor. For the characterization of the accompanying plasma surface interaction a thorough spectroscopic diagnostic of the W influx into the plasma is of utmost importance. In order to upgrade the experimental and theoretical spectroscopic data beyond the present use of the W-I transition (5d(5)6s(7)S(3)-5d(5)6p(7)P(4)) at 4008 angstrom, an extension to lines of other (preferably longer) wavelengths has experimentally been carried out and accompanied by calculations. The survey resulted in an assessment of four additional lines in the longer (4294.61, 4886.90, 4982.59 and 5053.28 angstrom) and two in the shorter wavelength range (2551.35 and 2681.42 angstrom). The lines emitted from tungsten particles which were released by the plasma from tungsten plates and limiters in the TEXTOR edge plasma were observed with different (also high resolution) spectrometers and the Zeeman pattern was studied in order to identify possible influences of nearby interfering plasma spectral lines. The effect of the ground state level population as well as cascading from higher levels is included in the calculation of the relative line intensities and of the respective S/X B-values, the conversion factor for photon into particle fluxes. Measured and calculated S/XB-values for the 4008 angstrom line agrees well whereas some of the other lines are probably strongly affected by not yet identified factors

Spectroscopic observation of Si I- and Si II-emission lines in the boundary of TEXTOR and comparison with kinetic calculations

Measurements of Si I- and Si II-emission lines were performed in the front of a test limiter under two different conditions: (i) silicon is sputtered from a silicon layer deposited on a graphite test limiter, (ii) silane is puffed into the plasma through a gas inlet in the limiter head, setting Si-atoms free from the dissociation of SiD4 molecules. It was shown that the relative intensities of the emission lines within the multiplets are in good agreement with theoretical data calculated in the SL-coupling scheme. The values for 'ionization per photon' were calculated for the electron temperature range below 100 eV using the GKU kinetic code and compared with measured ones. The measured and theoretical values for the Si II-emission lines are in reasonable agreement within a deviation of 30%. It was found that experimentally measured values for Si I lines match the calculated ones only when a LTE-population of 3p(2) SL terms (P-3, D-1 and S-1) is assumed