Wiki source code of Info collection for the BAM
Version 9.1 by sndueste on 2022/09/07 11:46
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8.1 | 1 | === Some basic stuff: === |
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1.1 | 2 | |
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8.1 | 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 ... | ||
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1.1 | 8 | |
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8.1 | 9 | === Data structure === |
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1.1 | 10 | |
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9.1 | 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"]]** |
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1.1 | 12 | |
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5.1 | 15 | = General information for the data analysis of pump-probe experiments = |
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1.1 | 16 | |
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5.1 | 19 | please have a close look to the publication: |
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1.1 | 20 | |
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5.1 | 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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1.1 | 26 | \\ |
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5.1 | 28 | Here is a summary of the ideas: |
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1.1 | 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 ! | ||
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5.1 | 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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4.1 | 35 | |
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6.1 | 38 | \\ |
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4.1 | 39 | |
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7.1 | 40 | {{info title="Correction of pump-probe delay"}} |
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4.1 | 41 | * BAM measurement: difference between electrons and timing system |
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5.1 | 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 | ||
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4.1 | 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 | ||
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6.1 | 49 | {{/info}} |