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1 -== Some basic stuff: ==
1 +== Some general stuff: ==
2 2  
3 -* (% style="color: rgb(255,0,0);" %)The relevant data is the arrival time FLASH.SDIAG/BAM/4DBC3/LOW_CHARGE_ARRIVAL_TIME
4 -* (% style="color: rgb(255,0,0);" %)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 -* (% style="color: rgb(255,0,0);" %)There are LOW and HIGH charge channels. For now the LOW_CHARGE Channel is the relevant one.
6 -* (% style="color: rgb(255,0,0);" %)Bigger numbers indicate later arrival time of the electrons
7 -* (% style="color: rgb(255,0,0);" %)The arrival time should be within -20 ps and +20 ps - otherwise there might be a problem ...
3 +* (% style="color: rgb(0,0,0);" %)There are several BAMs in FLASH. Essentially one in the accelerator section  (FL0.DBC2, Previously: 4DBC3) and one close to the respective undulator section (FL1.SFELC and FL2.SEED5).
4 +* (% style="color: rgb(0,0,0);" %)The BAM measures the arrival time for each single electron bun in the bunch train (for working principle see [[MSK SDiag Projects>>url:https://confluence.desy.de/display/SDiagPublic/MSK+SDiag+Projects||style="color: rgb(0,0,0);" shape="rect"]] or literature listed below) 
5 +* The data format of the BAM has been completely altered in the 2022 shutdown
6 +* (% style="color: rgb(0,51,102);" %)before 2022 BAMs were always saving the arrival time information for each 1µs bucked regardless if there were electrons in the accelerator or not. In addition the arrival times for  FL1 and FL2 were saved in the same parameter ...
7 +* (% style="color: rgb(0,51,102);" %)THIS is now different. There are new parameters saving only the arrival times for pulses that go to FL1 and to FL2 (in detail: first time slot of the accelerator and second)
8 +* (% style="color: rgb(0,51,102);" %)(typically) Bigger numbers indicate later arrival time of the electrons
9 +* (% style="color: rgb(0,51,102);" %)The arrival time should be within -20 ps and +20 ps - otherwise there might be a problem ...
8 8  * (((
9 -(% style="" %)
10 -(% style="color: rgb(255,0,0);" %)The actual time t0 = 0ps is an arbitrary offset which is only changed after setting up the system after, e.g., a maintenance time, and has no relevance.
11 -
12 -(% style="" %)
13 -(% style="color: rgb(255,0,0);" %)What one usually does, after defining/finding time zero in the experiment, is either observe the relative changes for a single bunch during the course of the measurement run compared to the starting point,
14 -
15 -(% style="" %)
16 -(% style="color: rgb(255,0,0);" %)or (in addition) observe the relative deviation across all bunches within the same bunch train.
17 -
18 -(% style="" %)
19 -(% style="color: rgb(255,0,0);" %)Those deviations and drifts happen usually only in the order of 50fs to 200fs; depending on the machine setup.
20 -
21 -(% style="" %)
22 -(% style="color: rgb(255,0,0);" %)The short-term timing jitter (over several 100 trains) for each individual bunch, i.e. the standard deviation from their mean value, is usually ~~ 20fs.
23 -
24 -(% style="" %)
25 -(% style="color: rgb(255,0,0);" %)The actual measurement resolution of a BAM can be - currently - as good as 3fs, for each bunch in the full train.
11 +(% style="color: rgb(0,51,102);" %)The actual time t0 = 0ps is an arbitrary offset which is only changed after setting up the system after, e.g., a maintenance time, and has no relevance.
26 26  )))
13 +* (((
14 +(% style="color: rgb(0,51,102);" %)What one usually does, after defining/finding time zero in the experiment, is either observe the relative changes for a single bunch during the course of the measurement run compared to the starting point, or (in addition) observe the relative deviation across all bunches within the same bunch train.
15 +)))
16 +* (((
17 +(% style="color: rgb(0,51,102);" %)Those deviations and drifts happen usually only in the order of 50fs to 200fs; depending on the machine setup.
18 +)))
19 +* (((
20 +(% style="color: rgb(0,51,102);" %)The short-term timing jitter (over several 100 trains) for each individual bunch, i.e. the standard deviation from their mean value, is usually ~~ 20fs.
21 +)))
22 +* (((
23 +(% style="color: rgb(0,51,102);" %)The actual measurement resolution of a BAM can be - currently - as good as 3fs, for each bunch in the full train.
24 +)))
27 27  
28 28  == Data structure ==
29 29  
30 -(% 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"]]**
28 +* (% 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"]]**
29 +* also see  [[doc:FLASHUSER.Data Acquisition and controls.Data Access at FLASH (DAQ, gpfs,\.\.\.).Offline data analysis (DAQ).The FLASH HDF5 structure.WebHome]]
31 31  
31 +{{info title="Correction of pump-probe delay"}}
32 +* (% style="color: rgb(255,0,0);" %)Here will be soon a link to a python notebook showing an example how to use the BAM data
33 +{{/info}}
34 +
32 32  \\
33 33  
34 34  = Publications related to BAM =
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46 46  
47 47  1. Evgeny Savelyev, et al, 
48 48  //Jitter-Correction for IR/UV-XUV Pump-Probe Experiments at the FLASH Free-Electron Laser//,
49 -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"]]\\
52 +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"]]
50 50  1. (((
51 51  Dennis Mayer, Fabiano Lever and Markus Gühr,
52 52  //Data analysis procedures for time-resolved x-ray photoelectron spectroscopy at a SASE free-electron-laser//,
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81 81  \\
82 82  
83 83  \\
84 -
85 -{{info title="Correction of pump-probe delay"}}
86 -* (% style="color: rgb(255,0,0);" %)BAM measurement: difference between electrons and timing system
87 -** (% style="color: rgb(255,0,0);" %)usually the BAM signal has to be added to the delay ...
88 -** (% style="color: rgb(255,0,0);" %)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
89 -{{/info}}
BAM-basics and outlook-2018_DESY-template_16-9Format.pdf
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FLASH-seminar-2011_BAM_study_results.pdf
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