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Wiki source code of Info collection for the BAM

Version 8.1 by sndueste on 2020-06-10 15:23
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1 === Some basic stuff: ===
2
3 * The relevant data is the arrival time FLASH.SDIAG/BAM/4DBC3/LOW_CHARGE_ARRIVAL_TIME
4 * 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 {{code language="none"}}/FL2/Timing/start time flash2{{/code}}))
5 * There are LOW and HIGH charge channels. For now the LOW_CHARGE Channel is the relevant one.
6 * Bigger numbers indicate later arrival time of the electrons
7 * The arrival time should be within -20 ps and +20 ps - otherwise there might be a problem ...
8
9 === Data structure ===
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11 (% style="color: rgb(0,0,0);" %)The details about the functionality and the data structure can be found on the page: (%%)**[[ BAM Data Structure>>doc:SDiagPublic.BAM Data Structure]]**
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15 = General information for the data analysis of pump-probe experiments =
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19 please have a close look to the publication:
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21 Evgeny Savelyev, et al,  //Jitter-Correction for IR/UV-XUV Pump-Probe Experiments at the FLASH Free-Electron Laser//,
22 New J. Phys. **19**, 043009 (2017), [[https:~~/~~/doi.org/10.1088/1367-2630/aa652d>>url:https://doi.org/10.1088/1367-2630/aa652d||shape="rect"]]
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24 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.
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28 Here is a summary of the ideas:
29
30 == Streak camera info ==
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32 * the streak camera measures the delay between optical (amplified) laser and FEL (dipole radiation). - not in respect to the master clock !
33 * streak camera ONLY delivers data which is averaged over several 10 seconds. There is NO shot to shot info.
34 * 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 ...)
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40 {{info title="Correction of pump-probe delay"}}
41 * BAM measurement: difference between electrons and timing system
42 ** usually the BAM signal has to be added to the delay ...
43 ** it is the best to test addition/subtraction and check the results on a step function (more/less sharp) - if there is no change of the data with + and - there is anyway something wrong. please contact your local contact for more information / help
44 * Streak camera: difference between electrons and optical laser
45 ** it is a slow signal and should only be used as a rolling average over multiple minutes
46 ** if you see a drift in the streak camera which you do not see in the BAM it is resulting from the optical laser
47 ** if this (BAM - streak camera signal) is significant e.g. 200 fs over 1 h, it means the drift compensation was probably off and it should be compensated
48 ** addition/subtraction is dependent on the setup and have to be checked
49 {{/info}}