Development Of Large Diameter Pulsed Penning Discharge Device

High current pulsed electron beam (HCPEB) is developing as materials surface modification tool in recent years. When high current electron flux transferring its energy into thin surface layer with short time, superfast processes is happened such as heating, melting, evaporation and consequent solidification, dynamic stress induced may impart the surface layer in the same time. It can improved physic-chemical and mechanical properties.One kind of large diameter pulsed Penning discharge device was self-designed to form the plasma anode of diode used in high current pulsed electron beam source. Helmholtz coils was adopted to generate parallel magnetic field, and the magnetic field intensity is controlled by the charging voltage of pulse capacitor where the largest value reaches0.2T. For the Penning anode power supply, the voltage is adjustable and ranges up to5000V with pulse capacitor of20FμF and shunt resistor of40Ω. According to the tests in vacuum condition of7.0×10-3to6.0×10-2Pa, the Penning discharge was separated into three stages, including activating, high current discharge and extinction stages. The formation of high current discharge was influenced severely by the combination of vacuum pressure, magnetic field intensity and anode voltage applied. And a certain activating time was needed obligatorily. It was found that the anode threshold voltage decreased along with the increased vacuum pressure and magnetic filed intensity, and the activating time was shortened with higher anode voltage and magnetic field intensity. The experimental phenomena were explained successfully with Paschen law on considering the existence of magnetic field.When the magnetic field strength is higher than the magnetic field threshold value in the certain anode voltage, anode current and the anode voltage is rendered approximately proportional relationship. And the anode peak current is nothing to do with the magnetic field strength, it can be seen that the magnetic field strength play a role of activating the discharge process and controlling the channel shape. While the anode current is directly affected by the anode voltage, the current limiting resistor and a charging capacitor control.Pulse penning discharge equipment showed a good stability in the whole operation process. Activation time showed good stability as well as the discharge time of large current phase and the anode current.