A study of pulsed high voltage driven hollow-cathode electron beam sources through synchronous optical trigger

In this study,a pulsed,high voltage driven hollow-cathode electron beam sources through an optical trigger is designed with characteristics of simple structure,low cost,and easy triggering.To validate the new design,the characteristics of hollow-cathode discharge and electron beam characterization under pulsed high voltage drive are studied experimentally and discussed by discharge characteristics and analyses of waveform details,respectively.The validation experiments indicate that the pulsed high voltage supply significantly improves the frequency and stability of the discharge,which provides a new solution for the realization of a high-frequency,high-energy electron beam source.The peak current amplitude in the high-energy electron beam increases from 6.2 A to 79.6 A,which indicates the pulsed power mode significantly improves the electron beam performance.Besides,increasing the capacitance significantly affects the highcurrent,lower-energy electron beam more than the high-energy electron beam.

Formation of Ti-N graded bioceramic layer by DC hollow-cathode plasma nitriding

Ti-N graded ceramic layer was formed on titanium by using DC hollow-cathode plasma nitriding technique. The structure of Ti-N layer was analyzed using X-ray diffractometry(XRD) with Cu Kα radiation, and the microhardness( HV0.1) was measured from the surface to inner along the cross section of Ti-N layer. The results indicate that the Ti-N graded layer is composed of ε-Ti2 N, δ-TiN and α-Ti(N) phases. Mechanism discussion shows that hollow-cathode discharge can intensify gas ionization, increase current density and enhance the nitriding potential, which directly increases the thickness of the diffusion coatings compared with traditional nitriding methods.

Theoretical model and experimental investigation optically triggered hollowcathode discharge formation

In order to investigate the process of optically triggered discharge formation,a model of ion space-charge formation based on classical plane electrodes and revised for a characteristic hollow-cathode discharge(HCD)configuration is proposed in this paper.The primary modified factor in our model is the penetrating electric-field parameter,which influences the ionization of trigger electrons and is calculated via particle simulation.Optical-trigger experiments are carried out using different voltages and under different seed-electron conditions,provided by two different photocathodes,Cu and Mg.The ion-accumulation rates calculated by our model are compared to the discharge-formation time,which is deduced from optical-trigger experiments.The results demonstrate that the process of positive space-charge formation is dominant in the HCD formation process or trigger delay,which is highly dependent on the seeding-electron density and applied voltage,and can therefore be quantitatively described by our model.Additionally,electron-beam generation is investigated by optically triggered HCD experiments on Mg-and Cu-photocathode-based devices.The results show that a more efficient trigger device is capable of generating an electron beam with higher amplitude and density.