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Abstract The reliability of cathode is critical to electric propulsion systems. Although researchers have carried out many life tests on hollow cathode, the discharge current is almost steady when the cathode is independently tested for life. Actually, when it is coupled with the thruster, the discharge current is with large amplitude low-frequency oscillation. Therefore, we suggest a new external circuit for a cathode-independent life test, which could simulate the characteristics of discharge current oscillation when the cathode is coupled with Hall thruster. We carried out 160 h of life test using the normal external circuit and the new external circuit, and the variation characteristics of the cathode orifice area are also studied during the life test. The results show that under the normal external circuit, the growth rate of the cathode orifice area initially increases and then decreases gradually with the increase of the time of life test, whilst the cathode orifice area in the new external circuit linearly increases. The new external circuit can provide a new method to simulate the discharge current oscillation when the cathode is coupled with Hall thruster during the independent life test of the cathode. [ABSTRACT FROM AUTHOR]