I fixed the used spark gap and put it into the trigger generator this morning. In the afternoon, I tested the trigger generator, it worked very well. It's better to buy a new spark gap as a backup, I contacted Chip Yang from General Atomics, because they did not produce this part, he transferred my email to another company(Dave Drury at L-3 Titan PSD, Email: email@example.com).
The X-ray cathode pulse was not good yet, Mike asked me to cut the cathode power supply cable reducing the pre-discharging. I did cut the end of x-ray cathode power supply cable, the cathode spark gap trigger became better than before. However it could not be moved forward to x-ray anode pulse peak. It's very hard to cut that power cable, it took me whole afternoon, I did not have more time to check the PCB board. I will ask Mike to help me check the circuit board tomorrow.