A Picosecond Pulsed Cold-Cathode Electron Gun for Ultrafast Electron Characterization and High-Frequency Radiation Source Applications

Ultrafast and ultrashort pulsed electron beams with high peak energy facilitate important applications, such as ultrafast electron characterization and high-frequency radiation source. The development of electron gun device, which simultaneously meets the requirements of ultrashort duration, high efficiency, and miniaturization, remains a challenge. Here, a carbon nanotubes cold-cathode electron gun by a photo-electric synergistic excitation is proposed, to successfully generate an ultrafast and ultrashort pulsed electron beam with repetition frequency of 1 MHz and pulse width of 278 ps. With optimizing the gun structure, a high-performance electron beam was obtained with averaged (peak) beam current over $38~\mu $ A (137 mA), averaged (peak) current density over 0.12 A cm $^{-{2}}$ (435 A cm $^{-{2}}\text {)}$ , and electron transmittance higher than 64%, co-excited by electrostatic field of 1.88 V $\mu $ m $^{-{1}}$ and peak laser intensity of 7.68 MW cm $^{-{2}}$ . This electron gun shows advantages of low excitation threshold, narrow pulse width and directly generating modulated electron beam from the laser excitation.