Physical Design of a Compact High-energy Electron Source Applied to On-site Non-destructive Testing

X-ray is widely used in non-destructive testing of electrical equipment. Radio frequency (RF) electron linear accelerator can generate $\sim$ MeV high-energy X-ray with strong penetrating ability, but the system is too large to be suitable for on-site testing. Whereas, the accelerator working at X-band (X-linac) can compress the facility scale over 2/3 at the same energy, which is convenient for on-site non-destructive testing of electrical equipment. As the key components of the X-linac, traveling wave (TW) tube, focusing coils, and RF couplers are designed in this context. The optimal phase velocity distribution of TW tube is realized by using the multi-objective genetic algorithm, the design of focusing coils is realized based on MATLAB, and the design of RF couplers is performed in CST Microwave Studio. In the end, an X-linac with a capture ratio of more than 90%, the energy spread of less than 10%, and average energy of about 3 MeV is obtained.