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Changes for page Filter-Units

Last modified by sndueste on 2025-04-23 17:45
From version 23.1
edited by sndueste
on 2021-08-17 16:55
Change comment: There is no comment for this version
To version 24.1
edited by sndueste
on 2021-08-19 14:11
Change comment: There is no comment for this version

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21 21  The shown transmission values for the filters are based on the [[CXRO webpage>>url:http://henke.lbl.gov/optical_constants/filter2.html||shape="rect"]] AND on measurements performed at the PTB (data see below).
22 22  
23 23  {{info}}
24 -The measured transmissions may differ from calculated ones in certain wavelength ranges significantly. Since we do not have measured values for all filters / thicknesses there may be situations where the shown transmission may be e.g. smaller for a thinner filter of the same material (since it was measured) in comparison to a thicker (not measured) one ...
24 +We tried to use the measured transmission where ever we have measured data. The measurement in the end includes e.g. oxide layers that may alter the transmission significantly ( see example for Al below).
25 +
26 +Thus the displayed transmission may be different from the CXRO calculations using the pure filter material (with out oxide layers).
27 +
28 +Since we do not have measured values for all filters / thicknesses  and wavelength ranges there may be situations where the shown transmission may be e.g. smaller for a thinner filter of the same material (since it was measured) in comparison to a thicker (not measured) one ...
25 25  {{/info}}
26 26  
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59 59  
60 60  == Filter transmission - expert info ==
61 61  
62 -* The transmission data for the transmission calculation in jddd uses combined data from CXRO and the measures transmission from BESSY. This is also the reason that for some values there is a deviation from expected scaling (e.g. same material but different thickness) or tabulated values. The calculated data for extrapolating the experimental values  was scaled to fit the experimental values at the crossover
63 -* [[image:attach:2020-09-16 14_51_08-combined filter transmission for server.opju _ - __win.desy.de_home_sndueste_My .png||height="250"]]
64 -* However comparing the transmission data for Al 100 nm and 200 nm for the measured (PTB) and calculated (CXRO) data shows a rather good agreement for 17 nm and shorter WL while at longer WL a systematic difference can be seen. future measurements with the FEL have to be done ... 
65 -* {{view-file att--filename="Al_filters.pdf" height="250"/}}The transmission data can be found at e.g. (depending on the filter wheel) /export/doocs/server/blfilters2_server/data/ as files generated from CXRO. We use the WL range 0.5 nm to 60 nm
66 +* The transmission data for the transmission calculation in jddd uses combined data from CXRO and the measures transmission from BESSY.
67 +* Thin oxide layers may alter the transmission significantly. As was found for the thin Al foils a transmission of 6 nm (2x3nm) Al,,2,,O,,3,, fits well with the measured data - at least much better as compared to only using Al without oxide layer.
68 +* [[image:attach:100 nm Al measured transmission_with Oxid.png||height="250"]][[image:attach:200 nm Al measured transmission_with Oxid.png||height="250"]]
69 +* The transmission data can be found at e.g. (depending on the filter wheel) /export/doocs/server/blfilters2_server/data/ or [[Laser operation Schedule 2021 - FS-LA Operations - DESY Confluence>>url:https://confluence.desy.de/display/FSLAOP/Laser+operation+Schedule+2021||shape="rect"]] as files generated from CXRO. We use the WL range 0.5 nm to 60 nm
66 66  * Transmission of filters calculated from CXRO  as pdf for [[FLASH1>>attach:TransmissionFilterwheel_FLASH1.pdf]] and [[FLASH2>>attach:TransmissionFilterwheel_FLASH2.pdf]] filter wheels
67 67  * [[attach:AllFiltersPTB.pdf]]: Transmission of filters as measured by PTB as pdf (and here are the [[actual data of the measurements>>attach:DESY_KW17_15_Filter.zip]])
68 68  * [[attach:Transmission_PTB_CXRO.pdf]]: Transmission of Nb, Zr, Al, Si Luxel filters measured between 2.5nm and 25nm by the PTB in comparison with CXRO data
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