Attenuation

Monochromatic beam attenuation                     White beam attenuation        

BM16 is equipped with both white beam & monochromatic beam attenuators; under normal circumstances you should only need to use the monochromatic attenuators. Monochromatic beam attenuation is carried out using 4 aluminium foils of varying thicknesses (0.2, 0.5, 0.9 & 1.5 mm). These can be used in different combinations to sensitively tune the attenuation level.

For normal data collections at BM16 attenuation is usually not needed unless your crystals are very small/thin or are otherwise radiation sensitive. However, attenuation is required for manual energy-scans so that the MCA coupled to the fluorecence detector does not become saturated. Remember: start with a high attenuation factor and work towards a smaller attenuation factor..

Monochromatic beam attenuators

The attenuators are controlled in MxCube by selecting an attenuation level between 0 and 15 from the Monochromatiic Attenuators brick.

Or with the commands matt_set and matt_status within the PX window:

PX> matt_status (gives current status of attenuation)

PX> matt_set (followed by a 'numeric value 0-15' inserts attenuator filters as detailed in the table below).

matt_set 0 removes all filters. Note: The attenuators are removed automatically by the fluorescence scan macro.

White beam attenuators

If in special cases you need to use the white beam attenuators (please consult your LC before doing this) - go to the SPEC PX session and type:

PX> mv att2 2 (This corresponds to a 0.5 mm Al foil)

or

PX> mv att2 3 (Al 1 mm)

or

PX> mv att2 4 (Al 2 mm)

PX> mv att2 1 removes all the white beam attenuators.