Last modified by sndueste on 2025/02/06 10:58
From version 2.1
edited by sndueste
on 2019/10/02 09:22
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To version 10.1
edited by sndueste
on 2022/09/07 17:39
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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))
1 +== Some basic stuff: ==
3 3  
4 -\\
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.
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
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,
15 15  
16 -\\
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 17  
18 -* if DBC3 is not working then also 3DBC2 can be used. there is a linear correlation between BC2 and BC3
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.
19 19  
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.
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 +
20 20  \\
21 21  
22 -=== more Info: ===
34 += Publications related to BAM =
23 23  
36 +=== BAM principle ===
37 +
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"]]
42 +
24 24  \\
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
45 +=== Two publications showing how to use the BAM data to improve the time resolution: ===
29 29  
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 +)))
55 +
56 +=== Publications showing the correlation between the values measured by the BAM and the XUV pulse arrival time ===
57 +
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"]]
30 30  \\
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 +)))
31 31  
32 -== Streak camera info ==
81 +\\
33 33  
34 34  \\
35 35  
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 ...)
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}}