Last modified by sndueste on 2025/02/06 10:58
From version 4.1
edited by cpassow
on 2020/04/23 17:41
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To version 9.1
edited by sndueste
on 2022/09/07 11:46
Change comment: There is no comment for this version

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1 -* the relevant data is the Arrivaltime FLASH.SDIAG/BAM/4DBC3/LOW_CHARGE_ARRIVAL_TIME
2 -* besides the arivaltime 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}}))
1 +=== Some basic stuff: ===
3 3  
4 -\\
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 ...
5 5  
6 -* There are now (since March 2017) LOW and HIGH charge channels. for now the LOW_CHARGE Channel is the relavant one.
7 -* bigger numbers indicate later arrivaltime of the electrons
8 -* the arrivaltime sould be within -20 ps and +20 ps . otherwise there might be a problem ...
9 -* There is a BAM status parameter: FLASH.SDIAG/BAM/4DBC3/BAM_STATUS.1 (the 1 indicates FLASH1)
10 -** bit 0 (value: 1) = data is valid,
11 -** bit 1 (value: 2) = at least 1 bunch is present,
12 -** bit 2 (value: 4) = calibration is on,
13 -** bit 3 (value: 8) = internal feedback is on,
14 -** bit 4 (value: 16) = tuning mode is on
9 +=== Data structure ===
15 15  
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>>url:https://confluence.desy.de/display/SDiagPublic/BAM+Data+Structure||shape="rect"]]**
12 +
16 16  \\
17 17  
18 -* if DBC3 is not working then also 3DBC2 can be used. there is a linear correlation between BC2 and BC3
15 += General information for the data analysis of pump-probe experiments =
19 19  
20 20  \\
21 21  
22 -=== more Info: ===
19 +please have a close look to the publication:
23 23  
24 -\\
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"]]
25 25  
26 -* [[LINK to detailed infos from MSK (may only work inside DESY network)(% class="confluence-embedded-file-wrapper confluence-embedded-manual-size" %)~[~[image:url:http://hasfweb.desy.de/pub/TWiki/TWikiDocGraphics/external-link.gif~|~|width="13" height="12"~]~]>>url:http://www.desy.de/~~mbock/pages/BAM_daq_channel_descriptions.html||rel="nofollow" shape="rect" class="external-link"]]
27 -* [[talk by Marie (2011)>>attach:FLASH-seminar-2011_BAM_study_results.pdf]]
28 -* contact: Marie Kristin Czwalinna
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.
29 29  
30 30  \\
31 31  
28 +Here is a summary of the ideas:
29 +
32 32  == Streak camera info ==
33 33  
34 -\\
35 -
36 36  * the streak camera measures the delay between optical (amplified) laser and FEL (dipole radiation). - not in respect to the master clock !
37 -* streak camera ONLY delivers data which is averaged over several 10 seconds. there is NO shot to shot info.
38 -* a larger value of the streak camera delay indicates that the optical laser comes later than the FEL (or FEL earlier than the laser ...)
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 ...)
39 39  
40 40  \\
41 41  
42 -== Calculate pump-probe delay ==
38 +\\
43 43  
40 +{{info title="Correction of pump-probe delay"}}
44 44  * BAM measurement: difference between electrons and timing system
45 -** the BAM signal has to be added, but it seems that the sign is the different for FLASH2
46 -** it is the best to test addition/subtraction and check the results on a step function (more/less sharp)
47 -
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
48 48  * Streak camera: difference between electrons and optical laser
49 49  ** it is a slow signal and should only be used as a rolling average over multiple minutes
50 50  ** if you see a drift in the streak camera which you do not see in the BAM it is resulting from the optical laser
51 51  ** 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
52 52  ** addition/subtraction is dependent on the setup and have to be checked
49 +{{/info}}