Synchronizing the seed pulse

Previously we used the pulse generator to trigger the Prometheus, actually the trigger pulse should be generated from the front end excimer laser system. So I tried to send the laser pulse to trigger the Prometheus today. I set the laser repetition rate at around 4 Hz, then it was divided by 10 times, this 0.4 Hz pulse was the main pulse to trigger the Prometheus. I used a photodiode to measure the front end laser pulse. There was a jitter about ~4 microseconds between the Thyratron trigger and the laser pulse.