Fig. 1. Schematic of experimental setup. The theta pinch comprises a glass vessel (length: 40 cm; internal diameter: 19.5 cm) surrounded by a six-turn copper solenoid coil, and a Rogowski coil, a photodiode, and a streaked spectrograph are used to obtain multiple parameters of the plasma therein.

Fig. 2. Typical temporal profiles of drive current (red) and luminosity (blue) measured at 20 Pa and 18 kV with a time resolution of 0.01 µs.

Fig. 3. Time-dependent image of H_β spectra corresponding to discharge cycles 6–9 in discharge at 18 kV and 20 Pa.

Fig. 4. Time-dependent density and temperature of plasma in half-cycles 7 and 8 at 18 kV and 20 Pa as extracted from Fig. 3. The shaded regions show the corresponding error ranges.

Fig. 5. Drive current (green), luminosity (black), electron density (blue), and electron temperature (red) in discharge half-cycle 7 at 18 kV and 20 Pa. The data are from Figs. 2 and 4 as measured simultaneously in one discharge experiment. Note that positive and negative current indicate only its direction in the primary loop.

Fig. 6. Schematic of configuration involving Lee model Reproduced from Lee et al., “A model code for the radiative theta pinch,” Phys. Plasmas 21, 072501 (2014) with the permission of AIP Publishing LLC.

Fig. 7. (a) Experimental data for radial implosion phase with the three sub-phases marked at the top of the graph; the data are from Fig. 5, and the dotted lines are to guide the eye. (b) Radial trajectories of shock front (SF, red curve) and current sheath (CS, blue curve).

Fig. 8. Experimental data for axial phase and anomalous heating phase, with the axial phase divided into two sub-phases as marked at the top of figure. The data are from Fig. 5, and the dotted lines are to guide the eye.

Fig. 9. (a) Schematic illustrating the reason for the second density peak. (b) CCD image showing formation of sausage instability during axial phase; the shoot began at time (f) with an exposure time of 20 µs.