[en] Photoelectric detectors of two types were developed for determining time-resolved soft X-ray spectra (energy lower than 1 keV) in the Rebex 2 machine. Both types of detectors use to advantage the photoelectric effect on a metal surface. The detector of the first type is a simple vacuum photodiode with an Al₂O₃ photocathode with a direct photoelectric current output matched to 50 Ohm. The detector is suitable for detecting X-ray emission from high-density (above 10¹⁶ cm^-3) and high-temperature (100 eV) plasmas with a high time resolution (about 1 ns). The detector of the latter type is designed for recording low X-ray emission fluxes. Its detection sensitivity was increased using a photomultiplier with an aluminium-coated plastic scintillator for monitoring accelerated photoelectrons. The arrangement, however, limits time resolution to some 10 ns. (J.U.)

[en] Ultrasoft X-ray plasma diagnostics was implemented by using X-ray diodes with Al photocathodes and submicrometer nitrocellulose filters. The design, clibration and characteristic properties of the apparatus are described. The main results of REB-heated plasma diagnostics are presented as an example of use. (author). 8 figs., 10 refs

[en] The time dependent intensities of selected resonance lines of oxygen impurity in ionization stages O²⁺ - O⁵⁺ in a hydrogen plasma with an electron density about 10¹⁵ cm^-3, are calculated by using the nonstationary corona model with variable electron temperature of a maximum value of 20 - 50 eV (plasma parameters of the REBEX experiment), to judge the possibilities of measurements in preparation and to facilitate their interpretation. Simultaneously, the rough form of XRD signals corresponding to these parameters, and the influence of radiation losses on plasma decay are shown. (author). 24 figs., 2 tabs., 15 refs

[en] Light elements like nitrogen or carbon are suggested as optimum working media for small Z-pinches (several kJ energy input). It is shown that such elements can be ionized up to K-shell ionization stages not only in hot-spots, but also in the bulk plasma. The yield of nitrogen K-shell radiation (about 10 J/shot) is therefore substantially higher than that of the conventionally used neon. In addition to pinch physics and radiation dynamics, such radiation could be of interest for applications in the 'water window' spectral region. (author) 1 tab., 4 figs., 8 refs

[en] The non-stationary corona model was used for the calculation of time-dependent soft X radiation spectra of REB-heated hydrogen plasma with 1% of oxygen. Electron impact ionization and excitation, spontaneous radiative decay and radiative and dielectronic recombination were taken into account. The plasma temperature was assumed to increase instantaneously to several tens of eV at the time t=0, remaining constant afterwards. The set of differential equations for ionization states of oxygen was solved using the Euler method. The plasma radiation spectra were computed in the range of 5 eV to 5 keV. The intensity of the continuum radiation component was is found to be not higher than 1% of that of the impurity lines. The theoretical signals of several X-ray detectors with various filters, calculated on the base of the time-dependent spectra obtained, may be directly compared with experimental data. (J.U.). 25 figs., 2 tabs., 26 refs

[en] The photomultipliers comprise multi-alkali or bi-alkali photocathodes (types Sb-K-Cs and Sb-Na-K) and box and venetian-blind multiplier systems. THe dynodes consist of either a AgMg alloy or an antimony-cesium emitter on a nickel backing. The system is described of photomultiplier designations set by Czechoslovak standards. The specifications are shown in table of Czechoslovak photomultipliers. (H.S.)

No abstract available

[en] Ultrasoft X-ray detectors (vacuum photodiodes) and submicrometer nitrocellulose filters were used for the electron temperature measurements of an electron beam-heated plasma in the REBEX machine. The relatively high X-ray intensity observed can be explained by the influence of impurity lines with carbon as a prevailing impurity. In the dense plasma region (10¹⁵ to 10¹⁶ cm^-3) the plasma bulk temperature was estimated to be 12 eV, with a slight trend towards increasing even after the termination of beam injection. In the lower density region (10¹⁴ to 10¹⁵ cm^-3), the electron temperature of the bulk exceeded some 50 eV. The soft X-ray data well correlate with the diamagnetic data. In both regimes, a relatively high fraction of overthermal electrons was evidently present. (J.U.). 3 figs., 4 refs

[en] The non-stationary corona model is used for calculations of time-dependent radiation spectra of a hydrogen plasma with a small amount of oxygen impurity, heated by a pulsed high-current relativistic electron beam. Two series of calculations were made - with a constant (step-like) temperature and with a more realistic time-dependent temperature. It is shown that under the REBEX conditions the radiation losses represent the dominant loss mechanism. Using computed spectra, the theoretical signal of the X-ray diode used for X-radiation measurements in the REBEX facility was calculated and compared with the experiment. (J.U.). 8 figs., 5 refs

[en] The VUV emission model of a hydrogen plasma with oxygen impurity (T_e=tens of eV, n_e∼10¹⁴ -10¹⁶ cm^-3, n_imp=1-3% n_e) is constructed in order to assess various possibilities of plasma diagnostics (especially T_e measurements) in the REBEX experiments. Two sets of calculations based on the nonstationary corona model are performed: time dependent continuous and line spectra in the range 5 eV to 5 keV in the constant T_e approximation (discussion of T_e measurements by the filter-method); and time dependent intensities of selected spectral lines (2s-2p type) of ions O²⁺-O⁵⁺ at variable T_e (including plasma heating by REB and radiative cooling). The feasibility of determining the plasma energy content from radiation losses is shown. (author) 2 tabs., 11 figs., 16 refs