Last modified by sndueste on 2025/02/06 10:58
From version 9.1
edited by sndueste
on 2022/09/07 11:46
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To version 10.1
edited by sndueste
on 2022/09/07 17:39
Change comment: There is no comment for this version

Summary

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1 -=== Some basic stuff: ===
1 +== Some basic stuff: ==
2 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 ...
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 ...
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.
8 8  
9 -=== Data structure ===
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,
10 10  
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"]]**
15 +(% style="" %)
16 +(% style="color: rgb(255,0,0);" %)or (in addition) observe the relative deviation across all bunches within the same bunch train.
12 12  
13 -\\
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.
14 14  
15 -= General information for the data analysis of pump-probe experiments =
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.
16 16  
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.
26 +)))
27 +
28 +== Data structure ==
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"]]**
31 +
17 17  \\
18 18  
19 -please have a close look to the publication:
34 += Publications related to BAM =
20 20  
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"]]
36 +=== BAM principle ===
23 23  
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.
38 +1. (% style="color: rgb(23,43,77);" %)A. Angelovski, et al.(%%)
39 +(% style="text-align: left;" %)//Evaluation of the cone-shaped pickup performance for low charge sub-10 fs arrival-time measurements at free electron laser facilities
40 +//(% style="color: rgb(23,43,77);" %)Phys. Rev. ST Accel. Beams (% style="text-align: left;" %)**18**(% style="color: rgb(23,43,77);" %), 012801 (2015)(%%)
41 +[[https:~~/~~/doi.org/10.1103/PhysRevSTAB.18.012801>>url:https://doi.org/10.1103/PhysRevSTAB.18.012801||style="text-align: left;" rel="nofollow" shape="rect"]]
25 25  
26 26  \\
27 27  
28 -Here is a summary of the ideas:
45 +=== Two publications showing how to use the BAM data to improve the time resolution: ===
29 29  
30 -== Streak camera info ==
47 +1. Evgeny Savelyev, et al, 
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"]]\\
50 +1. (((
51 +Dennis Mayer, Fabiano Lever and Markus Gühr,
52 +//Data analysis procedures for time-resolved x-ray photoelectron spectroscopy at a SASE free-electron-laser//,
53 +J. Phys. B: At. Mol. Opt. Phys. **55**, 054002 (2022); [[https:~~/~~/doi.org/10.1088/1361-6455/ac3c91>>url:https://doi.org/10.1088/1361-6455/ac3c91||style="text-decoration: none;" shape="rect"]]
54 +)))
31 31  
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 ...)
56 +=== Publications showing the correlation between the values measured by the BAM and the XUV pulse arrival time ===
35 35  
58 +1. (% style="color: rgb(0,0,0);" %)//** Description of the FLASH synchronization system**//
59 +S. Schulz, et al.(%%)
60 +(% style="text-align: left;" %)//Femtosecond all-optical synchronization of an X-ray free-electron laser//(% style="color: rgb(0,0,0);" %),(%%)
61 +(% style="color: rgb(0,0,0);" %)Nature Communications (% style="text-align: left;" %)**6**(% style="color: rgb(0,0,0);" %), 5938 (2015); (%%)[[http:~~/~~/dx.doi.org/10.1038/ncomms6938>>url:http://dx.doi.org/10.1038/ncomms6938||style="text-decoration: none;text-align: left;" shape="rect"]]
36 36  \\
63 +1. //**Showing a correlation of 11 fs rms between BAM and XUV arrival time
64 +**//R. Ivanov, et al to be published 2022  //**
65 +\\**//
66 +1. (((
67 +//**Showing a correlation of 20 fs rms between BAM and XUV arrival time**//
68 +R. Ivanov, J. Liu, G. Brenner, M. Brachmanski and S. Düsterer,
69 +//FLASH free-electron laser single-shot temporal diagnostic: terahertz-field-driven streaking//,
70 +Special Issue (PhotonDiag2017),
71 +J. Synchrotron Rad.** 25**, 26-31 (2018);[[ https:~~/~~/doi.org/10.1107/S160057751701253X>>url:https://doi.org/10.1107/S160057751701253X||style="text-decoration: none;" shape="rect"]]//**
72 +**//
73 +)))
74 +1. (((
75 +//**Study of arrival time fluctuations**//
76 +Ivette J. Bermúdez Macias, Stefan Düsterer, Rosen Ivanov, Jia Liu, Günter Brenner, Juliane Rönsch-Schulenburg, Marie K. Czwalinna, and Mikhail V. Yurkov,
77 +//Study of temporal, spectral, arrival time and energy fluctuations of SASE FEL pulses//,
78 +Optics Express 29, 10491-10508 (2021); [[https:~~/~~/doi.org/10.1364/OE.419977>>url:https://doi.org/10.1364/OE.419977||style="text-decoration: none;" shape="rect"]]
79 +)))
37 37  
38 38  \\
39 39  
83 +\\
84 +
40 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
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
49 49  {{/info}}