Sm. Turnbull et al., A QUANTITATIVE LASER SCHLIEREN METHOD FOR MEASUREMENT OF NEUTRAL GAS-DENSITY IN HIGH-PRESSURE GAS SWITCHES, Measurement science & technology, 4(10), 1993, pp. 1154-1159
A quantitative laser schlieren technique has been developed to measure
the changes in neutral gas density inside a spark gap switch after br
eakdown. The measurement system incorporates an array of narrow laser
beams which are used to probe the inter-electrode gas volume at discre
te distances from the spark axis. Changes in the refractive index grad
ient within the switch, caused by variations in neutral gas density, r
esult in beam deflection, which is measured using a neutral density we
dge/photodiode combination. The resulting Schlieren profiles yield bot
h spatially and temporally resolved refractive index data, which enabl
e calculation of the gas density. The use of four averaged trials to o
btain the final neutral gas density profiles minimizes errors caused b
y the turbulent nature of the cooling gas. A typical set of results is
presented for SF6 at a pressure of 0.5 bar.