Trigger Howto

Version 6.1 by sndueste on 2019/09/17 13:36

Introduction

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 detailed description can be found in x2Timer manual.

in short: the triggers are for low impedance (~50 OHM terminated ?? ), 5V triggers with an adjustable width. The main control panel 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 panel) ports at the rack.

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


different trigger events (starting points)

one can configure each channel for an individual trigger event

FLASH1

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"



FLASH2

trigger No

function

22

Trig116 + first bunch of FLASH2 - this trigger is shifted when FL2 starts at a different start time

181

shifts with the start 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 first and finally in 0.9 ns steps for fine adjustment.


Expert panels


image2019-9-17_13-10-56.png    image2019-9-17_13-8-46.png

With the "Expert overview" one gets the overview over all channels available on the timing card and can configure the card. This is useful to look what channels are using clock settings or burst mode settings that one wants to change ... and using the other tabs one can set parameters for clocks and bursts (see below)


For each trigger channel there is in addition a expert panel to set the properties of THIS channel

image2019-9-17_13-14-52.png  image2019-9-17_13-15-38.png




Set a constant frequency to a channel
image2019-9-17_13-18-9.pngimage2019-9-17_13-18-37.png



The timer card provides the option to generate  frequencies that are synched to the FEL reprate on the ps level. One can set 3 Clocks by deviding the reference frequency of 54.2 MHz by n. Please check before changing a frequency of it is used for some other channel !!

Since our main FEL frequency is 100.31 MHz the dividers are not straight forward:

Clock frequency

Devider to be set

"1 MHz" (1000.31 kHz)

53







  • 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 choice . 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 expert panel (see below) has to be used. The Trigger in the user panel (see above) has to be set to 0 !!!
    mtcatrigger2k.png

here an example defining the bunch pattern for FLASH1 to mask 1


here is a link to the old VME trigger system