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Ultrafast Electron Diffraction/Microscopy (UED/UEM) are powerful tools for directly observing ultrafast dynamic processes at the atomic level. The quality of the electron beam is crucial for image resolution, but the space charge effects can degrade parameters such as energy spread and emittance, reducing the spatiotemporal resolution. By reducing the charge per electron bunch and increasing the emission frequency, the space charge effect can be effectively suppressed, ensuring a high signal-to-noise ratio in the images. Superconducting Radio Frequency (SRF) photocathode guns can operate in continuous wave (CW) mode and generate highly stable and bright electron beams, making them promising electron sources for the next generation of UED/UEM. This paper aims to optimize the design of a 1.4-cell SRF gun using Nb3Sn for UED/UEM. The focus is on minimizing thermal losses in the cavity to enable efficient conduction cooling and ensure stable operation at 4K in the superconducting state. Furthermore, beam dynamics analysis of the electron beam inside the cavity is performed to assess beam quality for different charges and bunch sizes. This enables us to achieve a high-quality electron beam that meets the design requirements.
Jia-lian et al. (Mon,) studied this question.