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Trigger Howto

The MTCA based triggers have a jitter in the few ps range, the delay can be shifted in 1 ns steps (over many ms), one can choose between 10 Hz triggers, frequencies locked to the pulses (e.g. 1MHz) and the actual bunch patterns. A detailled description can be found in x2Timer manual. And here is the little talk that was given in the group meeting Oct 2014

in short: the triggers are for low impedance (~50 OHM terminated ?? ), 5V triggers with an adjustable width. The main controlpannel for the x2 timer has the control options for the 3 front modules (connected with a RJ45 cable - connecting to a "trigger box" with 2 trigger exits (Lemo) each) and 8 Lemo exits at the back of the crate. in the BL-beamline case these triggers are connected to the BNC (patch pannel) ports at the rack.

The main control can be done with a simplified user panel which can handel the timing in respect to the FEL pulses and not in respect to some (arbitrary) reference time ( Event) Trigger_scheme.gif

there is a more advanced control pannel (by MCS4) to change more subtile parameters:


one can configure each channel for a trigger event


trigger No function
16 the MCA trigger 3.11 ms before the Flash1 pulses (same as A6 but more stable)
166 A6 event. still possible to use but less precise than 16
162 A2 event as earliest ( 24 ms before the FEL)
224 E0 event of the BL fast shutter ( 19 ms before the FEL)
225 E1 event of the PG fast shutter ( 19 ms before the FEL)
21 Trig16 + first bunch of FLASH1 - this trigger is shifted when FL1 starts later than "700"


trigger No function
22 Trig116 + first bunch of FLASH2 - this trigger is shifted when FL2 starts at a different start time
181 shifts with thestart time of FLASH2 as event 22 but comes 22 ms ! before the FEL
from this trigger as starting point one can shift the timing in 9 ns steps forst and finally in 0.9 ns steps for fine adjustment.


  • in order to generate a stable frequency one has to set the input source to FPGA clock (and use dividers to get the desired frequency)
  • to generate the burst patterns of the FEL one has to choose a trigger event (best 116 for FLASH 2 and 16 for FLASH1) and activate Destination 1 for FLASH1 and Destination 2 for FLASH2 . finally one has to assign the activated Bunch pattern mask to the trigger channel of choise . now the pattern can be shifted and the trigger width can be changed as with the 10 Hz triggers. IMPORTANT: to move the bunchtrain to the desired starting point the DELAY in the expertpennal (see below) has to be used. The Trigger in the user panel (see above) has to be set to 0 !!!
here an example definging the bunch pattern for FLASH1 to mask 1

here is a link to the old VME trigger system

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