Changes for page Trigger Howto

Last modified by sndueste on 2023/07/07 11:28

From 9.1 to 8.1 From 15.1 to 14.1

From version 14.1

edited by grunewal
on 2019/12/06 13:59

Change comment: There is no comment for this version

To version 9.1

edited by sndueste
on 2019/09/17 14:22

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--XWiki.grunewal
++XWiki.sndueste

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  {{toc/}}
--= Introduction (user panel)
-- =
++= 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>>attach:x2Timer.pdf]] ([[Design Paper>>url:http://ttfinfo2.desy.de/doocs/Timing/CDRv2.2short.pdf||shape="rect"]]).
++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>>attach:x2Timer.pdf]].
  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)
++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)[[~[~[image:url:http://hasfweb.desy.de/pub/Setup/TriggerHowto/Trigger_scheme.gif~|~|alt="Trigger_scheme.gif" width="800"~]~]>>attach:Trigger_scheme.gif]]
--[[image:attach:Trigger_scheme.gif]]
++
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--= Different trigger events (starting points) =
++= different trigger events (starting points) =
  one can configure each channel for an individual trigger event
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--= Set a constant frequency to a channel =
--
--=
++= Set a constant frequency to a channel
  [[image:attach:image2019-9-17_13-18-9.png||height="250"]][[image:attach:image2019-9-17_13-18-37.png||height="149"]] =
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++\\
++
  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 (using the Expert overview ) 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:
--[[image:attach:image2019-9-17_14-22-29.png||width="450" align="right"]]
--
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  |=(((
  Clock frequency
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  )))
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  Once a clock is configured with the right frequency one can choose in the "expert panel" of the according channel the "FPGA clock" in the "input source select"  chooser.
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++One has to set the
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++[[image:attach:image2019-9-17_14-22-29.png||width="450"]]
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--One has to set the delay to values less than the repetition rate ... (so for 1 MHz between 0 and 990 µs)  and the trigger width also less than the rep rate ...
++This results in a continuous train of pulses with the set trigger width
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++* 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 !!!**
++[[~[~[image:url:http://hasfweb.desy.de/pub/Setup/TriggerHowto/mtcatrigger2k.png~|~|alt="mtcatrigger2k.png" width="607" height="458"~]~]>>attach:mtcatrigger2k.png]]
--This results in a continuous train of pulses with the set trigger width :
++here an example defining the bunch pattern for FLASH1 to mask 1
--= Creating an (own) burst trigger =
--
--One can use now a SECOND trigger channel which is set to a regular 10 Hz trigger  and gate the clock output to create a burst with defined start point and length,
--
--For the example we use the FRONT.TRG2 (BL3 Trg5) as gate pulse which defines the length of the burst (set with the trigger width) and the (rough) starting point of the burst. This trigger is only used as gate and the physical trigger output is NOT used.
--
--The  second channel (here FRONT.TRG3 (BL3 Trg6) which is set to the clock frequency defines the reprate (by the FPGA clock setting) , the exact starting point of the first trigger ( by the delay ) and the width of the  MHz/kHz triggers (width).
--
--**To get from the clock to the burst trigger** one has to:
--
--* set the  "2nd source select" to the gate trigger ( here FRONT.TRG2) - this defines a second source to considder for the trigger output.
--* and the "output source select" to "AND 2nd Ch."  this finally only sends a trigger if on both inputs (clock and gate) we have a high signal.
--
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--[[image:attach:image2019-9-17_14-35-5.png||height="250"]]                        [[image:attach:image2019-9-17_14-34-38.png||width="400"]]
++[[here is a link to the old VME trigger system>>doc:FLASH.VMETrigger]]
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--
--= Real bunch trigger  - get a trigger for each FEL pulse =
--
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--
--Sometimes it is convenient to get a trigger pulse for each pulse in the FEL. thus if the FEL number of bunches or reprate are changed, the trigger adapts accordingly.
--
--For this one has to select the source of interest in the expert overview panel (tab: "Bunch pattern") ... well for us this is FLASH1 (FL1D) or FLASH2 (FL2D)
--
--There are 6 different bunch pattern "channels" one can configure. Typically only 2 are needed ... And in each one there are 6 selectors to choose sources . We only need one - it does not matter in which one is used.
--
--[[~[~[image:attach:image2019-9-17_14-51-28.png~|~|height="250"~]~]>>attach:image2019-9-17_14-51-28.png]][[image:attach:image2019-9-17_14-47-15.png||thumbnail="true" height="199"]]
--
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--In the expert panel one can now choose the configured "Bunch Pattern" as "Input source select"
--
--**NOTE: To shift the burst in time one can no longer use the delay of the individual channel BUT the delay in the "Bunch pattern" tab in the expert overview! This now shifts all bursts ... so you better know what you are doing. typically the burst is already shifted to the actual FEL timing ... Shifting the timing should be discussed with the beamline scientist / local contact ...**
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--[[image:attach:image2019-9-17_15-4-47.png||height="250"]][[image:attach:image2019-9-17_14-52-40.png||height="250"]]
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