• Filter control
  • General infos
  • Calculation of the transmission
• More (special) info
  • Mounted filters, replacement in N2 box
  • Filter transmission - expert info
  • Documentation of the filter protection in jddd
  • Data collection of FEL parameters and Filter damage

Filter control

General infos

The filter control panel can be used to move in filters AND to calculate the transmission of the fundamental wavelength of the FEL and its 3rd harmonic.

The moving procedure is supervised by a protection system. First of all the fast shutter is closed before moving the filter wheel (to protect the filters during moving) and blocked till the movement is over. Then the fast shutter has to be opened again with the Fast shutter control button. It does not open automatically! 

In addition the pulse energy and the number of bunches in the FEL is monitored. IF the radiation dose exceeds a certain limit the filters can not be moved into the beam. Then the beam has to be attenuated using the gas attenuator to a range where the filters can be used again. More info: JdddFilterProtection

Current limits are:    :

Calculation of the transmission

The shown transmission values for the filters are based on the CXRO webpage AND on measurements performed at the PTB (data see below).

The transmission is given for the fundamental Wavelength and in addition for the third harmonic of the FEL ( which is typically 1% of the fundamental). The bars below the shown transmission are just a guide to the eye to distinguish between large and weak transmission easier. The values are calculated for the current wavelength set in the FEL. 

Since for certain combinations of filters the transmission of the third harmonic can be significantly higher than for the fundamental it may happen that more third harmonic as fundamental passes ... thus there is a warning indicating that this may be a problem ...

By pressing on the transmission values of a certain filter one can open the window showing the transmission as function of the photon energy / Wavelength:

To help finding the right filter setting one can also have an overview of all filters available and look on the transmission for a certain wavelength / photon energy independent of the actual FEL wavelength. Using the tab "transmission" one can type in a photon energy or wavelength → press "calculate transmission" and then see transmission of the fundamental and the 3rd harmonic for this wavelength ... (this is a separate transmission calculator and playing with it does not alter anything on the filter wheels or in the FEL / undulator settings!)

More (special) info

Mounted filters, replacement in N2 box

• Filter History and mounted filters of FLASH1 and FLASH2: what filter was mounted at which motor position
• Replacement filters in N2 flow box

Filter transmission - expert info

• 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.  
• 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 
• Transmission of filters calculated from CXRO  as pdf for FLASH1 and FLASH2 filter wheels
• AllFiltersPTB.pdf: Transmission of filters as measured by PTB as pdf (and here are the actual data of the measurements)
• 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
• Experimental measurements for the transmission: Laurents transmissiont measurements for "Rohringer" Beamtime - shows deviations for Si !

Documentation of the filter protection in jddd

• JdddFilterProtection

Data collection of FEL parameters and Filter damage