There are several advantageous features of using a pseudospark (PS) discharge [1] for electron beam production. One of these features is the formation of an ion channel following the pseudospark anode, which enables the beam to propagate and eliminates the need for a guiding magnetic field [2][3][4][5]. When a high voltage is applied to the hollow cathode, the electric field across the anodecathode gap penetrates a short distance into the hollow cathode region due to the small cathode aperture. A PS discharge will occur if the pressure in the system is suitably low (typically 50-500 mTorr) so that the discharge is at the left-hand side (with respect to the minimum) of the Paschen curve. In such a PS discharge condition, the gas breakdown will occur along the longest possible path, allowing a virtual anode to form, extending from the anode into the hollow cathode region. As the virtual anode reaches the cathode surface field-enhanced emission begins to occur. Electrons begin emitting from the cathode surface at an increased rate, augmented by secondary emission and are accelerated toward the aperture by the electric field. Consequentially this rapid increase in electron emission results in a rapid increase in the beam current. As the beam propagates through the anode its front edge ionizes the background gas, forming a plasma channel, while the following beam electrons expel part of the plasma electrons so that an ion-channel is formed, confining the beam and eliminating the need for any external magnetic guide field. A high current density, high brightness electron beam with a sweeping voltage can therefore be generated and propagated by ion channel focusing.Pseudospark discharges have been explored for various important applications, especially high quality electron beam generation for microwave sources [2,5,6] and potential terahertz devices. High frequency sources above 100 GHz are very attractive for a wide range of research and technical applications, including molecular spectroscopy, bio-imaging and security screening. As the frequencies move into the sub-terahertz and terahertz region, the size of device reduces greatly. This brings a challenge with regard to device fabrication. Therefore a compact and simplified structure is desirable, with the pseudospark-sourced electron beam an ideal choice for high power, high frequency sources. This paper presents some experimental results of the electron beam current dependence on the gap separation of a single-gap pseudospark structure. At a certain gap separation, the relationship between the beam current and discharge voltage has been studied [2]. It is found that the electron beam only starts to occur when the charging voltage is above a certain value and increases with the increasing discharge voltage following two tendencies. Under the same discharge voltage, the configuration with the larger electrode gap separation will generate higher electron beam current. Because the energy of the high brightness electrons in the beam produced by a pseudospark is relativ...