Mar 23, 2006 Timing Requirements for the Pockels Cell: General Timing: (1) The pockels cell is triggered when 4 conditions are ALL true: * PPS permitted * MPS permitted * trigger from the timing system running at a requested rate * trigger from the laser running at a constant rate (usually (always?) 120 hz) (2) There is no limit to the time between rate changes (either up or down). There are no stabilization requirements. (3) There is no rate input to the timing system from the laser control system so there is no way for the timing system to know if it's triggering at a rate higher than the laser. If for some reason it is, the extra triggers will be ignored. It's up to the user to configure the timing system so that this condition (and the resultant confusion) never happens. Pulse-to-Pulse Timing: (1) When the pockels cell trigger is coincident with laser trigger, beam is created. The shape and duration of the laser triggered is controlled elsewhere. To make sure the coincidence happens for a particular pulse, the timing trigger pulse width must be close to the full pulse of 8.3msec. It's possible the pulse width will need to be tuned (knobbed) to get the correct value. (2) The trigger pulse delay will need tuning to match the laser trigger. The ability to save and restore trigger delays (and maybe pulse width) is required. Decision when to Trigger: (1) The pockels cell trigger is driven by the needs of the user and the MPS input to the timing system. The user can request: (a) Single Shot - trigger one or more consecutive pulses (usually one) and stop. If MPS is requesting zero rate, the request is ignored. If MPS is rate-limited, the consecutive pulses will be done at the MPS rate. If the user asks for a single pulse but at a high rate, the timing system will keep track of the requests and not allow a rate higher then the MPS request. (b) Continuous - trigger one pulse at a specified rate until told to stop. If MPS is requesting a rate lower than the user request, the lower rate is used instead.