Laser shadowgraphy, schlieren and interferometry for characterizing conical wire array sources and self-magnetic-pinched diodes at CEA gramat

Summary form only given. A set of visible imaging techniques were used for diagnosing self magnetic pinched diodes and conical array-generated plasma jets on the ASTERIX generator (6 MV, 100 kA) and the OEDIPE test-bed used for SPHINX studies (950 kA, 1.2 μs), respectively. The selected experimental configurations allow for qualitative and quantitative 2-D time-resolved data to be obtained using schlieren shadowgraphy and interferometry imaging throughout plasma experiments. The setup consists of a continuous diode-pumped solid state laser, coupled to, either a light refraction-based optical system for shadowgraphy and schlieren techniques or a Mach-Zehnder setup for interferometric measurement. The images are collected with two high speed multi-frame CCDs. Shadowgraphy enables visualizing both the diode anodecathode gap closure (~ 120 ns), and the plasma jet formation and propagation over longer time scales (~1.8 μs). The Schlieren technique reveals plasma regions of high density gradients. Moreover, interferometric measurements allow for relevant plasma parameters such as the electronic density profile, the axial and radial plasma jet velocities to be inferred from interference fringes shift. The results obtained so far are presented and discussed.