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ID29 Attenuators

last modified 13-02-2008 08:55
ID29 Attenuators

 

There are two different sets of attenuators on ID29: white beam attenuators and monochromatic beam attentuators

 

The white beam attenuators are located just upstream of the monochromator in the optics hutch, while the monochromatic attenuators are located in the experimental hutch upstream of the slit box.

 

 

White Beam Attenuators (return to Quick Index)

 

There are 3 attenuator axes each with 4 different attenuating filters which can be inserted into the white (un-monochromated) X-ray beam. The beam "sees" axis 1 first (known for command purposes as "attf" standing for attenuator-front), axis 2 second ("attm", attenuator middle) and axis 3 third ("attb", attenuator back). Due to the power in the unattenuated white beam, it is necessary that attenuators be inserted in sequence i.e. if you wish to insert an attenuator from axis 2 (attm), then you must have previously inserted an attenuator from axis 1 (attf).

To move an attenuator into the beam you require to "send" it to one of its 5 different pre-set positions (4 different filters plus a position where the attenuator is completely removed from the beam). This is done from the filters tab within the Beamline ControlPanel GUI.

One of the most likely causes of "low or no" beam is when attenuators have been introduced and not removed.

The following white beam attenuators are available. The plots of the calculated transmission vs energy for each attenuator can be obtained by following its link.

 

Table of White Beam Attenuators (return to Quick Index)

 

position 1 2 3 4 5
attf (axis 1) empty 3mm pyro-carbon 5mm carbon ATJ 5mm pyro-carbon 10mm pyro-carbon
attm (axis 2) empty 0.93mm Al 1.84mm Al 2.43mm Al  2.9mm Al
attb (axis 3) empty 2.9mm Al  2mm pyro-carbon 1mm pyro-carbon 0.5 mm pyro-carbon

 

 

Monochromatic Beam Attenuators (return to Quick Index)

 

    The monochromatic attenuators are a series of independently controlled foils of varying thicknesses so that different foil combinations can give the desired beam intensity.


    The monochromatic attenuators are assigned values which follow a binary scale (1,2,4,8,etc..) with increasing attenuation factor. Different combinations of attenuators can be used by entering a mattset value between 0 (all out) - 255 (all in), e.g.,

     

      EXP> mattset 35 [inserts attenuators 32, 2 & 1]

      EXP> mattset 17 [inserts attenuators 16 & 1]

      EXP> mattset 2049 [inserts attenuators 1 & 2048]

       

     

     

    Table of Monochromatic Beam Attenuators (return to Quick Index)

     

    mattset 1 2 4 8 16 32 64 128 256 512 1024 2048
    thickness 0.1mm 0.25mm 0.5mm 1mm 2mm 4mm 0.1mm 0.25mm 0.5mm 1mm 2mm 4mm
    material pyro C pyro C pyro C pyro C pyro C pyro C Al foil Al foil Al foil Al foil Al foil Al foil

     

     

     

    Table of Monochromatic Beam Attenuator Transmissions (return to Quick Index)

     

    mattset 1 2 4 8 16 32 64 128 256 512 1024 2048
    Fe K-edge
    transmission    		 ? 71.4% 50.6% 27.3% 11.4% ? ? 1.39% 0.712% 0.538% 0.260% ?
    Cu K-edge
    transmission    		 ? 84.6% 71.2% 50.4% 26.9% ? ? 8.46% 0.711% 0.055% 0.039% ?
    Se K-edge
    transmission    		 ? ? ? ? 59.0% ? ? 35.0% 13.4% 5.20% 1.61% ?

     
 
European Synchrotron Radiation Facility