I-V characteristics and photocurrents of a He corona discharge under flow conditions

I-V characteristics of a helium corona discharge are discussed for both positive and negative modes. Experimental measurements confirm Townsend's theory for only a part of the I-V characteristic. The flow effect has been correlated to a pressure variation inside the discharge chamber, which in turn gives rise to a corona current change. Corona discharges produce UV radiation through excitation and recombination processes. Currents produced by electron extraction from a stainless steel surface located 74 mm away from the discharge have been measured. Corona currents in the range of 1-7 muA induce currents on the metallic target of 10-30 pA (positive corona), whereas currents of 15-50 muA give rise to 60-140 pA (negative corona).