CORRELATION OF LIGHT FLUCTUATIONS IN POSITIVE COLUMN OF AN ARGON DISCHARGE

The correlation coefficient of light fluctuations has been measured in an argon plasma in the positive column of a glow discharge at gas pressures between 0.02 and 0.08 torr and at discharge currents from 10 to 100 mA. At such conditions there are no stationary striations. The mean frequency and mean wavelength of the fluctuations are determined from correlation functions measured at zero time delay distance between sensors respectively. It has been found that the maximum of the correlation coefficient envelope moves towards the anode. The velocity of this movement has been determined. As some critical gas pressure at constant discharge current is approached all these quantities change sharply and well observed ionization waves appear.