Design And Experimental Study Of Vacuum Plasma Channel With Magnetic Confinement

In rencent years, as a novel technology of energetic beam, the non-relativistic, high-current electron beams are of great interest for material surface treatment and even found rather wide practical application. Through in-depth study, the new type of electron gun based on high-current Penning anode plasma source can produce the wide-area electron beam with uniform energy distribution on low pressure theoretically, which is a promising development. According to the requirement of novel high current pulsed electron beams (HCPEB) equipment, Penning discharge structure was designed and the formation mechanism of anode plasma channel was investigated.The anode of diameter 4.5,6 and 8 cm, anode voltage of 3-5 kV, magnetic voltage of 0～190 V and working pressure of 5.0～8.0×10-2 Pa were explored. The experiments showed that plasma discharging process consists of two stages, high voltage-low current and low voltage-high current. The maximum discharge current depends only on the anode voltage and shield resistance. Based on the discharge phenomenon, the working parameters for high density and homogeneity of plasma discharge were emphasized. As for the magnetic threshold voltage, it increases with the decreasing of anode diameter and increasing of anode voltage. The duration of high voltage-low current and rising time of discharge current decreases gradually and tends to a stable value with the increasing of working pressure. Finally, the optimized discharge conditions was selected as Penning anode diameter 8 cm, anode voltage 5 kV, magnetic voltage 170 V and working pressure 7.0×10-2 Pa, which correspond to a plasma discharge of good stability and formation of plasma channel of length 17.5 cm. Above of the parameters were selected to test formation of electron beams.It is found that the exceeded high density plasma formed in the channel in this condition, leading to the failed launching of electron beams. Then electron gun produce electron beams successfully in condition of the low plasma density in the channel.