Some basic stuff:

• The relevant data is the arrival time FLASH.SDIAG/BAM/4DBC3/LOW_CHARGE_ARRIVAL_TIME
• Besides the arrival time from FLASH1 there is also the FLASH2/3 electron arrival time saved. The BAM data is saved for the complete RF pulse. First bunches are from FLASH1 then there is a gap for switching and then there is a second part for FLASH2 (starting at the FLASH2 start time (recorded in DAQ as /FL2/Timing/start time flash2))
• There are LOW and HIGH charge channels. For now the LOW_CHARGE Channel is the relevant one.
• Bigger numbers indicate later arrival time of the electrons
• The arrival time should be within -20 ps and +20 ps - otherwise there might be a problem ...

Data structure

The details about the functionality and the data structure can be found on the page:   BAM Data Structure

General information for the data analysis of pump-probe experiments

please have a close look to the publication:

Evgeny Savelyev, et al,  Jitter-Correction for IR/UV-XUV Pump-Probe Experiments at the FLASH Free-Electron Laser,
New J. Phys. 19, 043009 (2017), https://doi.org/10.1088/1367-2630/aa652d

describing in detail the usage of BAM, streak camera and delay line data in order to get the actual time axis as reliable as possible.

Here is a summary of the ideas:

Streak camera info

• the streak camera measures the delay between optical (amplified) laser and FEL (dipole radiation). - not in respect to the master clock !
• streak camera ONLY delivers data which is averaged over several 10 seconds. There is NO shot to shot info.
• a larger value of the streak camera delay (typically) indicates that the optical laser comes later than the FEL (or FEL earlier than the laser ...)