PETRA-III Laser-wire

Fast Laser Synchronisation

This section describes how to sync the Fast laser with bunches in Petra. The SMB100A (RF source) is described and how to roughly sync using a frequency drift.

Synchronising the Laser with Bunches

The BKR provides a precision 10MHz reference signal from the timing racks in building 30. This is transported on a low-loss cable, via the Petra tunnel, to the laser hut and inserted into the Ref In BNC connector on the back of the SMB100A. More required on this

Triggering the LWDAQ

The fast laser has a TTL output from the synchroniser box which can trigger the LWDAQ. The existing timing, as well as delayed internal PXI trigger timing, is shown:

The 1DBuP synchroniser TTL output goes to the HP 8013B pulse generator (trigger in), and a delay of 600ns produced. The output (trigger +ve) goes to the PXI-6653 (PFI-3) in the PXI rack (Laser Trig). The signal is sent, via StarTriggerN to the PXI-5152 Digitizer, where the Calorimeter and Fast Photodiode are connected. The PXI-5152 has a trigger re-arm time of 1us, from the end of the trigger window, if the TDC is turned off.

The window for the digitizer should be 300ns long, to enable the re-arm time to be met ready the next laser pulse.