Timing System

System Description

The S20 timing system synchronizes the laser system with the accelerator and controls the internal timing within the laser system.

System Diagram - Uses SLAC timing / SLCNet

Diagram Source

Backup or "local" timing - When SLCnet is down

The conversion to local timing requires two DG645s. DG645a will generate 120 Hz that is used to trigger the regen. DG645b is externally triggered (by DG645a prescaled by 12) at 10 Hz. Precale is the term used by SRS to mean "divide". DG645b triggers the SAGAs, Preamp, Pulse slicer and cameras, all at 10 Hz. When triggering the laser system, the DG645s are placed by the rack in the back of the laser room and connected to the cables that go from the rack to the pacemaker and SDG. You do not need to adjust anything in the laser system, just plug the DG645s in as shown below. All the cables you need will be stored with the DG645s.

Notes

Both setups work, this is just for documentation. This is the timing on 5/15/23. It is not tracked with the diagrams above!

There is a timing difference of 100 us for the cameras when using SRS DG645s to locally trigger the laser+cameras. During normal operations the laser is supplied by triggers at 120 Hz (EC 50) and 10 Hz (EC 223), the cameras are triggers at 10 Hz (EC 223).

While writing this Brendan finds both -150 us and -50 us in the control system for the cameras, and I think -50 us is correct, so he has to check which one actually triggers the cameras.

The triggers for both systems and the difference between triggers and the regen are:

The common 100 nanosecond difference has to do with the some slip between the two DG645 boxes. I'm trying to figure out if the 100 microsecond difference for the cameras.

Locking the laser to RF

The procedure for locking the laser to RF is the same as the sector 10 laser: Enable RF Lock

The photodiode used to get the RF signal from the oscillator is connected to the timing system through a narrow bandpass filter. The photodiode voltage will not show up on the control panel unless the oscillator cavity length is close to correct. When locking, manually adjust the cavity length using the stepper motor to get the frequency within 50Hz, then check the voltage of the photodiode.

Timing laser and e-beam at IP

There are several methods and locations in sector20 at which synchronous time of arrival between e-beam and laser can be measured.

Delays

Axilens ionization at gas jet location

On

Tandem lens ionization

E320 collision interaction

EOS1

EOS2

EOS delay positions