Attainment of the Pease-Braginskii current in an ultra-high-pressure discharge

Results are presented from experimental studies of the contraction of the channels of discharges in hydrogen and helium at current amplitudes of 0.5-1.6 MA and initial gas pressures of 5-35 MPa. The observed decrease in the brightness temperature of the discharge channel with increasing deposited energy is caused by the heating of the ambient gas. The channel contraction observed near the maximum of the discharge current is due to the attainment of the Pease-Braginskii critical current. Previously, it was shown that megampere discharges operate in a fully metallic plasma of the eroded electrodes. The theoretical value of the Pease-Braginskii current for discharges in vacuum is ∼100-200 kA. The observed increase in the critical current to ∼1 MA is attributed to the absorption of channel radiation in the dense ambient gas.