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Experiments are performed using Langmuir probes to measure the plasma parameters in both steady‐state and I‐V modes in a low‐pressure Cs‐Ba diode. The data show that at low discharge currents the electron energy distribution function is nonMaxwellian due to the presence of an electron beam from the emitter. Also, the plasma properties were nonhomogeneous across the 1 mm diode gap; the electron temperature was 10%–15% higher and the plasma potential ∼1 V higher near the emitter, and the plasma density was a factor of three higher near the collector. The good agreement between calculations and experiment, in spite of the presence of the electron beam from the emitter, suggested that the beam electrons do not undergo collisions with Cs atoms in the gap. Experimental I‐V curves showed the presence of two different thermal emission currents, each corresponding to a different emitter work function, at the beginning and the end of the I‐V pulse. © 1995 American Institute of Physics.