[en] Recent results from x-pinches at the NTF provide experimental evidence for the existence of strong electron beams in x-pinch plasmas and motivate the development of a new diagnostic, x-ray spectropolarimetry, for investigating the anisotropy of such plasmas. This diagnostic is based on theoretical modeling of polarization-dependent spectra measured simultaneously by spectrometers with different sensitivity to polarization. Results of the first polarization-sensitive experiments at the NTF are presented. K-shell emission from Ti x-pinches is recorded simultaneously by two identical spectrometers with the dispersion plane perpendicular and parallel to the discharge axis. The spectroscopic analysis of more than eight Ti x-pinch shots show how spectropolarimetry complements the usual diagnostics of a z-pinch plasma. The polarization-sensitive spectra, generated by a Maxwellian electron beam at LLNL EBIT have been collected and analyzed. These data make an important contribution to the plasma polarization spectroscopy program at the NTF. In particular, the study of multiply-charged Ti ion spectra help in the interpretation of the polarization-sensitive spectra from Ti x-pinches at the NTF

[en] The measurements with temporal resolution are very important in studies of properties of radiation from hot dense plasmas (0.8< Te<1.5 keV, Ne up to 2-3·1022 cm-3) generated by a pulsed-power z-pinch machine with a current Imax∼0.8 divide 1.0 MA and a current rise time of 100 ns. To perform measurements of radiation from hot dense plasma an advanced 5-channel time resolved spectrometer 'Polychromator' was used. All channels are independent from each other and axially symmetric with respect to the main optical axis. An additional sixth channel sited on the main optical axis is used for device alignments and measurements using a time-integrated, spatially-resolved transmission diffraction grating spectrometer. A flexible design allows us to use different types of dispersing elements and detectors. A procedure of optical alignments of the device is described. Experimental data from time resolved channels as well as from a TGS channel are presented and briefly discussed

[en] An analysis of the energy, spatial character, and temporal evolution of electron beams and hard x rays from 0.9 to 1.0 MA high-Z X pinches is presented. Experimental results from Ti, Fe, Mo, and W X pinches show that X pinches are an effective source of hard x rays with energies greater than 30 keV. Electron beams with energies up to 2 MeV higher than the applied anode-cathode voltage are generated along the pinch axis before the maximum current is reached. The beams have diameters of about 3 mm and generate bursts of hard x rays with sizes between 1 and 2 mm and total time durations of up to 150 ns. The measured 100-500 keV x-ray distribution is spectrally anisotropic. Hard x-ray synchrotron radiation in the side-on direction is proposed as a possible explanation of this anisotropy

[en] Investigations of spectral sensitivity, contrast coefficient, and spatial resolution of widely used x-ray films have been undertaken at the P.N. Lebedev Institute. A description of experimental methodologies and results are presented. These studies were carried out using synchrotron radiation in the range of 20--150 angstrom. Spectral sensitivity and contrast coefficient dependencies on wavelength for Kodak 10106, DEF, RAR2490, and TPF films and spatial resolution for Kodak 10106 and RAR2490 films are presented and discussed

[en] The results from the last six years of x-ray spectroscopy and spectropolarimetry of high energy density Z-pinch plasmas complemented by experiments with the electron beam ion trap (EBIT) at the Lawrence Livermore National Laboratory (LLNL) are presented. The two topics discussed are the development of M-shell x-ray W spectroscopic diagnostics and K-shell Ti spectropolarimetry of Z-pinch plasmas. The main focus is on radiation from a specific load configuration called an 'X-pinch'. X-pinches are excellent sources for testing new spectral diagnostics and for atomic modelling because of the high density and temperature of the pinch plasmas, which scale from a few (micro)m to several mm in size. They offer a variety of load configurations, which differ in wire connections, number of wires, and wire materials. In this work the study of X-pinches with tungsten wires combined with wires from other, lower-Z materials is reported. Utilizing data produced with the LLNL EBIT at different energies of the electron beam the theoretical prediction of line positions and intensity of M-shell W spectra were tested and calibrated. Polarization-sensitive X-pinch experiments at the University of Nevada, Reno (UNR) provide experimental evidence for the existence of strong electron beams in Ti and Mo X-pinch plasmas and motivate the development of x-ray spectropolarimetry of Z-pinch plasmas. This diagnostic is based on the measurement of spectra recorded simultaneously by two spectrometers with different sensitivity to the linear polarization of the observed lines and compared with theoretical models of polarization-dependent spectra. Polarization-dependent K-shell spectra from Ti X-pinches are presented and compared with model calculations and with spectra generated by a quasi-Maxwellian electron beam at the LLNL EBIT-II electron beam ion trap.

[en] The paper presents the measurement results and comparison analysis of the emission characteristics of single- and double-cascade argon liners (fast Z-pinches). The experiments were conducted using GIT-4 inductive storage with up to 1,6 MA current through the load at 100 ns rise front. Application of two spectrographs enabling to acquire spectral dependence of emission within different ranges to conduct the experiments has allowed to determine temperature and mass both of hot and of relatively cold parts of plasma. It is shown that in case of double-cascade liners the rise of emission yield in argon K-lines occurs both due to the increase of plasma hot part temperature and due to the increase of plasma hot part mass. 12 refs., 5 figs., 2 tabs

[en] Electron beams in 400 kA peak current Mo and W X-pinches have been studied using 1 ns time-resolution Si diodes to monitor x rays >9 keV. Softer x rays were monitored by photoconducting detectors (PCDs). Three different types of higher energy x-ray bursts were observed. The first type appears to be produced by electrons generated starting at the moment of, or immediately after, the first thermal x-ray burst (typically 40-50 ns after the current start), and Si detector signals last 1-2 ns. The second type of harder x-ray burst occurs 50-80 ns after the current start, lasts 2.5-10 ns, and is typically not correlated with a thermal x-ray burst. These two types of bursts were generated near the cross-wire region. The third type of x-ray burst occurs 70-100 ns after the current start, and is also uncorrelated with PCD signals. The energetic electrons responsible for these x rays are generated for 10-30 ns, and the radiation is produced in the anode region

[en] A transmission grating spectrometer (TGS) with one dimensional spatial resolution was used to investigate the radiative properties of X-pinch plasmas produced using wires made of NiCr and CoNiCr alloys, and Mo. Experiments were carried out on the Cornell XP machine. The TGS was used to estimate of the energy yields of L-shell Cr and Ni, and M-shell Mo radiation. The absolute energy yields in the wavelength range 10<λ<15 A were 1-5% of the total energy delivered to the load (10-40 J for L-shell NiCr, and 20-50 J for M-shell Mo). An analysis of the spatial structure of X-pinch emission regions in different wavelength ranges shows that the source structure is changing with wavelength and the size varies from less than 0.1 up to 1 mm. For example, in one Mo X-pinch test shown, three separate soft x-ray sources radiating in the wavelength range λ<42 A can be seen, but only one of those sources radiates in the wavelength range λ>42 A. The results are compared with data obtained previously with the TGS on a 1 MA pulse powered machine Zebra

[en] This paper presents a detailed investigation of the temporal, spatial, and spectroscopic properties of L-shell radiation from 0.8 to 1.0 MA Mo x pinches. Time-resolved measurements of x-ray radiation and both time-gated and time-integrated spectra and pinhole images are presented and analyzed. High-current x pinches are found to have complex spatial and temporal structures. A collisional-radiative kinetic model has been developed and used to interpret L-shell Mo spectra. The model includes the ground state of every ionization stage of Mo and detailed structure for the O-, F-, Ne-, Na-, and Mg-like ionization stages. Hot electron beams generated by current-carrying electrons in the x pinch are modeled by a non-Maxwellian electron distribution function and have significant influence on L-shell spectra. The results of 20 Mo x-pinch shots with wire diameters from 24 to 62 μm have been modeled. Overall, the modeled spectra fit the experimental spectra well and indicate for time-integrated spectra electron densities between 2x10²¹ and 2x10²² cm^-3, electron temperatures between 700 and 850 eV, and hot electron fractions between 3% and 7%. Time-gated spectra exhibit wide variations in temperature and density of plasma hot spots during the same discharge

[en] The measured emission characteristics of single- and double-cascade argon gas puffs (fast Z-pinches) and their comparative analysis are presented. Experiments were performed in the GIT-4 generator with the inductive storage, with a load current of up to 1.6 MA and with a current-front duration of 100 ns. By using two spectrographs that provide measurements in different wavelength ranges, the electron temperatures and masses of the hot and cold plasma fractions are determined. In the case of the double-cascade gas puff, the increase in the K-radiation yield is shown to be due to an increase in both the temperature and mass of the hot plasma fraction