Stratification of the Positive Column of a DC Discharge in Nitrogen

Abstract

This paper studies the stratification conditions of the positive column of the dc glow discharge in nitrogen in tubes of various radii. In each discharge tube the striations are observed in closed regions with respect to current and applied voltage values within the limited range of gas pressure values. We revealed that the first striation (counted from the cathode end of the positive column) was clearer expressed and it possessed the maximum thickness. Striation length is weakly dependent on discharge current but it decreases with gas pressure growing. Again the striations with a large order number (counted from the cathode edge of the positive column) possess lesser thickness. We find out that positive column stratification obeys similarity laws well. The extinction curves and striation existence regions registered in different discharge tubes and plotted against the product of gas pressure and inter-electrode distance pL coincide. Reduced striation thickness d/R (striation thickness d divided by tube radius R) in different tubes also is in good agreement with each other when plotted against pR. We observe that the reduced striation thickness obeys the Goldstein-Wehner law d/R = C/(pR)m, the constants for nitrogen being C = 1.05 and m = 0.32.

Keywords

• direct current glow discharge
• positive column
• striations
• nitrogen
• low pressure