Synchronization of laser system with accelerator - December 2009

In this post, I will present some details about the synchronization of the laser system with the RF electron accelerator.

1 - A photodiode monitors the 75-MHz output of the Ti:S oscillator. This signal is transported to a Phase Lock Loop than synchronizes a 3-GHz Voltage Controlled Oscillator to this laser, with ability to control the phase. This system has been published by Kiewiet et al. in 2001. The laser oscillator is the main clock of the system. To match the derived 3-GHz frequency to the resonance frequency of the RF cavity, the laser cavity length can be changed by displacing one of the end mirrors.

2 - These two boxes allow us to trigger the laser system by one external trigger from the main Trigger and Delay Generator. One trigger to the laser system leads to a pulse from the high power pump laser of the amplifier and the pulse selection by the two Pockel Cells in the regenerative amplifier cavity. This system operates at 1-kHz frequency.

3 - Because the accelerator operates at 100-Hz or lower frequency the laser frequency is down shifted by the use of a chopper and shutter combination. The chopper decreases the frequency to 100-Hz from which a fast shutter can select only a single pulse or it sub harmonic. We perform this operation to prevent the cathode of the RF cavity of being exposed to too many laser pulses that can cause damage.

6 - In front you can see the shutter and in the back the vacuum laser transport line to the accelerator room.

7 - The chopper and shutter controllers. The chopper is synchronized to the 1-kHz trigger of the laser system. Then only the right phase has to be selected to pass the right laser pulse from the 1-kHz train.