Info collection for the BAM

* the relevant data is the Arrivaltime FLASH.SDIAG/BAM/4DBC3/LOW_CHARGE_ARRIVAL_TIME

* 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}}))

3

4

\\

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

\\

* if DBC3 is not working then also 3DBC2 can be used. there is a linear correlation between BC2 and BC3

19

20

=== more Info to the BAM: ===

21

22

* [[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"]]

23

* [[talk by Marie (2011)>>attach:FLASH-seminar-2011_BAM_study_results.pdf]]

24

* contact: Marie Kristin Czwalinna

\\

= General information for the data analysis of pump-probe experiments =

\\

please have a close look to the publication:

33

34

Evgeny Savelyev, et al, //Jitter-Correction for IR/UV-XUV Pump-Probe Experiments at the FLASH Free-Electron Laser//,

35

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

37

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.

\\

Here is a summary of the ideas:

42

43

== Streak camera info ==

44

45

* the streak camera measures the delay between optical (amplified) laser and FEL (dipole radiation). - not in respect to the master clock !

46

* streak camera ONLY delivers data which is averaged over several 10 seconds. There is NO shot to shot info.

47

* 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 ...)

\\

\\

* BAM measurement: difference between electrons and timing system

55

** usually the BAM signal has to be added to the delay ...

56

** 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

57

* Streak camera: difference between electrons and optical laser

58

** it is a slow signal and should only be used as a rolling average over multiple minutes

59

** if you see a drift in the streak camera which you do not see in the BAM it is resulting from the optical laser

60

** 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

61

** addition/subtraction is dependent on the setup and have to be checked

62

Wiki source code of Info collection for the BAM

Applications

Navigation