I. L. Beigman

Tungsten spectroscopy 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 (5d56s7 S3–5d56p7P4) at 4008 A, 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 A) and two in the shorter wavelength range (2551.35 and 2681.42 A). 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/XB-values, the conversion factor for photon into particle fluxes. Measured and calculated S/XB-values for the 4008 A line agrees well whereas some of the other lines are probably strongly affected by not yet identified factors.

Reflection of few-cycle x-ray pulses by aperiodic multilayer structures

We report on the numerical investigation of the reflection of extremely short (femto-and attosecond) x-ray pulses by multilayer structures (MSs). Periodic and aperiodic MSs are considered. We formulate the conditions whereby the reflection does not significantly change the pulse shape and length. The optimization of broadband aperiodic MSs from the viewpoint of the reflection of few-cycle pulses and the possibility of chirped-pulse compression are considered. It is shown that the power reflection coefficient can be appreciably higher than unity. Aperiodic MSs have been calculated which are capable of reflecting pulses comprising only three wave periods.

Extreme vacuum ultraviolet solar spectra obtained during the SPIRIT experiment aboard CORONAS-F: A catalog of lines in the range 280–330 Å

We present a catalog of 100 lines in the wavelength range 280–330 Å detected by the RES-C spectroheliograph in solar active regions and flares during the SPIRIT experiment aboard the CORONAS-F orbital station. We identified 54 lines. The line intensities recorded during the X3.4 (GOES) solar flare of December 28, 2001, are given. The data reduction procedure is discussed.

Reflection of atto-and femtosecond X-ray pulses from aperiodic multilayer mirror

The reflection of femto-and attosecond soft and hard X-ray pulses from multilayer structures (MSs) was investigated. The conditions are formulated under which the pulse shape and duration barely change upon reflection. The MSs are optimized for the reflection of extremely short pulses, and the possibility of compressing chirped pulses is considered. It is shown that the power reflection coefficient can be appreciably larger than unity. The aperiodic MSs capable of effectively reflecting pulses containing no more than three wave periods are calculated.

Solar EUV Spectra Obtained during the SPIRIT Experiment Onboard the CORONAS-F Satellite: A Catalog of Lines in the Range 176-207 ˚ A

We present a catalog of 65 spectral lines in the range 176–207 Å recorded by the RES spectroheliograph in active regions and flares during the SPIRIT experiment onboard the CORONASF satellite. We have identified 51 lines. The relative intensities of lines recorded during the M6.5 (GOES) flare of September 16, 2001, are given. The data processing technique is discussed.

Ionization of heavy ions in relativistic collisions with neutral atoms

The problem of ionization of ions in ion-ion and ion-neutral relativistic collisions is considered. Formulas for ionization cross sections are derived in the Born approximation in terms of the momentum transfer without allowance for magnetic interactions. Using these formulas implemented in the LOSS-R code, the ionization cross sections are calculated for the K shells of neutral atoms colliding with protons and also for 1s and 2p electrons of multiply charged heavy ions (nuclear charge Z = 80−90) colliding with bare nuclei and neutral atoms. The calculation results are compared with experimental data and calculations of other authors.

Ionization of heavy ions in collisions with neutral atoms at relativistic energies

Ionization processes of heavy ions colliding with atoms and ions at relativistic energies are considered. Formulaes for calculating ionization cross sections in the Born approximation using momentum-transfer representation without regard to magnetic interactions are given as well as those in dipole and impulse approximations. Using the LOSS-R [25] and HERION codes, calculations of relativistic cross sections are performed for H-like multiply changed ions with the nuclear charge Z ≈ 80−90, colliding with neutral atoms and for multiply changed uranium ions colliding with protons and carbon atoms. The results of calculations are compared with available experimental data and calculations performed by other authors.

Development of the concept of charge-exchange recombination spectroscopy for ITER

Charge-exchange recombination spectroscopy under ITER conditions is numerically simulated using the DINA code. The code allows one to calculate the attenuation of neutral beams in plasma, the intensity of atomic emission and emission from the ions produced by charge exchange with the neutral beam, and the intensity ratio between the emission related to charge exchange and the background continuum plasma emission. The cross sections for atom-ion interactions in plasma are calculated, and the excitation rates of spectral transitions in hydrogen-like impurity ions are determined. The measurement scheme and the main parameters of the spectrometer proposed for charge-exchange recombination diagnostics in ITER are described.