Time-resolved investigation of subnanosecond radiation from Al wire hybrid X pinches

K-shell x-ray spectra from Al wire hybrid X pinches have been studied using an x-ray streak camera with better than 0.1-ns time resolution together with a Focusing Spectrograph with Spatial Resolution (FSSR) spectrograph. High-intensity radiation with a continuumlike spectrum was observed in the subnanosecond initial phase of the x-ray pulse generated by the hybrid X pinch (HXP). The absence of spectral lines in this phase and the extremely small x-ray source size indicates the importance of radiative processes in the final phase implosion dynamics. Plasma parameters in the following phases of the HXP were determined from analysis of the line intensities. Point-projection radiography together with a slit-step wedge camera and an FSSR spectrograph without time resolution were used to show the number of radiation sources, and to give information on the time-integrated photon energy spectrum.

Figure 1

(a) Schematic drawing of the experimental arrangement for recording HXP radiation: (1) HXP, (2) PCDs, (3) XRD, (4) time-integrated SSW camera, (5) time-integrated x-ray pinhole camera, (6) crystal, (7) streak camera, (8, 9) imaging objects, (10) filters, (11) image plates, and (12) crystal for time-integrated FSSR spectrograph. (b) Hybrid X pinch with conical electrodes and its cross section.

Figure 2

Results obtained with a 66-μm-diameter Al wire HXP: (a) spectrum recorded on a sweep 2 (see Table 1); (b) enlarged part of the image in (a) with the spectra from three x-ray bursts; (c) time-integrated spectrum recorded by an FSSR spectrometer with a mica crystal in the same shot; (d) spectral profiles of all x-ray bursts shown in part (a) and (c); (e) signal from the PCD with a Ti filter is shown together with the load current waveform and sweep monitor signal. [Shot 8926].

Figure 3

Imaging diagnostics data for the shot, spectroscopic data from which are shown in Fig 2: (a) filter for SSW camera; (b) SSW image; (c) fragment of point-projection image of a mask with 250-μm diameter hole (29× magnification) and a fiber recorded with 61 times magnification. Filters are shown on the figure. (d) The image profile. Shot 8926.

Figure 4

Results obtained from a 66-μm-diameter Al wire HXP showing: (a) the time-integrated FSSR spectrum and its spectral profile; (b) spectra recorded on a sweep 4 (9 ns for the full screen) with profiles of all bursts; (c) the signal from a PCD with a 10-μm Be filter together with the load current and the sweep monitor signal; (d) and the temporal profiles of Heγ and ${\mathrm{H}}_{\beta }$ lines and continuum in time. Shot 8908.

Figure 5

Filters of SSW camera (a) and SSW image (b); fragment of point-projection image of a 250-μm diameter hole (magnification 29×) and a fiber with 15-μm diameter recorded with 61× magnification through a 10-μm Cu filter; (d) the image profile from the first two x-ray bursts. Shot 8908.

Figure 6

Spectra recorded in shot 8908 on a sweep 4 are shown magnified with profiles of the first burst showing variation in the linewidth as a function of time.

Figure 7

Calculations of the intensity of the lines made using the prism program: (a) the intensity of He-and H- like Al lines depending on the plasma temperature; (b) the linewidth depending on the electron density. The calculations were made at a source size of 20 μm.

Figure 8

Results obtained from a 66-μm-diameter Al wire HXP showing: (a) a spectrum recorded on a sweep 4; (b) current and signal from a PCD with a 25-μm Be filter (E > 1.5 keV). Shot 8905.

Figure 9

Results obtained with a 66-μm-diameter Al wire HXP showing: (a) a time-integrated FSSR spectrum with the spectral profile; (b) spectrum recorded on a sweep 5 with profiles of different portions of the recorded x-ray burst; (c) the PCD signal with a Be filter together with the load current and sweep monitor signal; (d) profiles showing intensities of Heγ, ${\mathrm{H}}_{\beta }$ lines and continuum in time. Shot 8911.