Author :
Cuneo, Michael E. ; Lockner, Thomas R. ; Tisone, Gary C.
Author_Institution :
Sandia Nat Labs., Albuquerque, NM, USA
Abstract :
The refractive index gradient (RING) diagnostic described uses a fast, silicon, photodiode quadrant detector with a differential amplifier to temporally detect the refraction of a CW laser by transient discharges or expansions of vapor, gas, or plasma. The method is a local one-dimensional time-resolved, quantitative, species-discriminating (i.e., atoms or electrons) Schlieren technique. The diagnostic is easy to field, sensitive (the minimum deflection angles detectable are ≈0.3 μrad), and fast (risetime=11±1 ns). Circuit design, performance, and diagnostic theory are discussed. To illustrate the utility of this technique, examples of measurements on LEVIS (laser evaporation ion source), a laser-produced, active, lithium ion source, are given. Measured properties include vapor/plasma production thresholds, expansion velocities, and time-resolved gradient and density spatial profiles. Comparisons of the RING results with measurements using a Faraday cup and a double-floating Langmuir probe are presented
Keywords :
optical variables measurement; plasma diagnostics; refractive index; schlieren systems; CW laser; LEVIS; Li ion source; Si photodiode quadrant detector; circuit design; deflection angles; diagnostic; differential amplifier; expansions; fast system; gas; laser evaporation ion source; local one-dimensional time-resolved quantitative Schlieren technique; plasmas; refraction; refractive index gradient; risetime; species discrimination; transient discharges; vapor; vapour production; Differential amplifiers; Ion sources; Laser theory; Photodiodes; Plasma diagnostics; Plasma measurements; Plasma properties; Refractive index; Ring lasers; Silicon;
