The laboratory generation and diagnosis of uniform near-critical-density (NCD) plasmas play critical roles in various studies and applications, such as fusion science, high energy density physics, astrophysics as well as relativistic electron beam generation. Here we successfully generated the quasistatic NCD plasma sample by heating a low-density tri-cellulose acetate (TCA) foam with the high-power-laser-driven hohlraum radiation. The temperature of the hohlraum is determined to be 20 eV by analyzing the spectra obtained with the transmission grating spectrometer. The single-order diffraction grating was employed to eliminate the high-order disturbance. The temperature of the heated foam is determined to be T = 16.8 ± 1.1 eV by analyzing the high-resolution spectra obtained with a flat-field grating spectrometer. The electron density of the heated foam is about N e = 4.0 ± 0.3 × 10 20 cm − 3 under the reasonable assumption of constant mass density.

Excimer lasers driven by linear transform driver (LTD) are expected to be used in inertial confinement fusion (ICF). The main problem of LTD in excimer lasers is synchronous triggering on multiple circuits, gas spark switches are important for synchronous triggering, which are required to be fired with low prefire probability and jitter. Multi-gap switch, as a kind of the gas spark switches, is always used in LTD. In this paper, a comparison study of corona discharge current of a multi-gap switch for LTD from the aspects of self-breakdown voltage and jitter is presented. The length of equalizingvoltage needle was optimized by the electrical strength simulation. Using the optimized needle, the corona currents of the two gaps were measured, then it was found that the corona currents differ when the lengths of the corona needles were equal. To study if the difference of current in each gap affects the breakdown voltage and jitter of the switch, the length of the needle was adjusted to make the corona current the same. Then the breakdown voltage and jitter were measured under the two conditions of equal and unequal corona currents. It can be found that smaller the difference of current in each gap, higher the breakdown voltage and lower the jitter of the switch. It can be concluded that the corona needle can be adjusted to make corona current of each gap equal, which can be beneficial to increase the breakdown voltage and lower the jitter of the switch.

The X-ray properties of Al plasmas were studied experimentally by using the excimer laser facility in the State Key Laboratory of Laser Interaction with Matte. Radiated fluxes were recorded within two X-ray diodes, and the relative spectral distributions were recorded within an X-ray flat-field grating spectrograph, respectively. Experimental results indicated that the major X-ray photons were between 60 eV and 360 eV. By employing the spectral integration method, the measured data were appropriately processed to obtain absolute energies of the X-ray that radiated from Al plasmas.

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