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  • data backup is triggered via crontab
    • $ crontab -l → lists all active crontabs
    • $ crontab -e → allows to change the crontabs
    • our crontab entry is
      • 5 * * * * /home/luxelab/LUXE320/dataBackup.sh
      • 5 * * * *  → run every 5 minutes
      • /home/luxelab/LUXE320/dataBackup.sh → shell script that does get executed
  • the backup script is dataBackup.sh contains

    • rsync -av --log-file=/home/luxelab/LUXE320/rsync.log /home/luxelab/LUXE320/data/ /media/luxelab/data1/backup_LUXE320/

    • -a → archive (fundamental backup option)
    • -v → verbose
    • --log-file → the verbose output is sent to rsync.log
    • source:  /home/luxelab/LUXE320/data/
    • destination: /media/luxelab/data1/backup_LUXE320/

Synchronization

One issue with the setup is, that the digitizer DAQ is not in the FACET network. Therefore, it has no synchronization of the events. Various options exist to synchronize the data. One option is using timestamps on both systems and synchronization via some protocol. This was not successful so far. The other option is to use the data itself.

Charge/Position Correlation

One idea is to use the charge and/or position dependence of a signal in both systems. This could be a BPM, toroid, or camera data from the EPICS side and signal amplitude in a straw on the LUXE EDS side. The events can be shifted such that the correlation between the two test variables is maximized.

Beam Background

The FACET DAQ provides the option, to perform a beam background measurement before a run/scan. In that case, the beam is blocked by the MPS shutter (Brendan, slack, 06/12) for some events. This gives a clear start signal.

Pockel Cell

The Pockel cell can control the electron beam on an event basis. The corresponding EPICS variable is TRIG:LT10:LS04:TCTL (Spencer, email, 06/16). The idea is that at the beginning of a run, the cell is activated/deactivated in a specific pattern that allows the events to be matched based on that pattern.

Machine/Beam Trigger

  1. open facethome (from the control network)
  2. navigate to the Experiment - LI20 section
  3. select the Triggers... menu in the FKG20-24 section
  4. our trigger is channel 2 in the front panel section, called trigger FP2
  5. we use the following settings
    1. beam trigger (coming from trigger RP2)
    2. normal polarity
    3. 1000 ns width
    4. 10 ns delay

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