Index:

ID01 - Experimental Hutch Reference Energy Filters

For calibrating the X-ray energy 9 reference filters with absorption edges from 5 keV to 39 keV can be inserted into the monochromatic beam (motor att21). These filters are mounted after the multilayer monochromator at the end of the optics hutch (OH1). The filter foils are rotated around the vertical axis by about 45 degrees with respect to the monochromatic beam for observing under 90 degrees the X-ray fluorescence with a PIN diode (counter att2).
 

Position     Mnemonics     Element     Thickness/um Edge/eV
0 Out - - -
1 Ti_7um Ti 7 4996
2 Cr_5um Cr 5 5989
3 Fe_8um Fe 8 7112
4 Cu_7um8 Cu 7.8 8979
5 Au_6um Au 6 14353
6 Mo_15um Mo 15 20000
7 Ag_25um Ag 25 25514
8 Sn_84um Sn 84 29200
9 La_100um La 100 38925

Dynamical absorbers system

The dynamic range of any of the detectors is much more limited than the intensity of the beam. In order to increase the linear dynamic range of the scintillator counter and other detectors, a system of dynamical absorbers has been installed. The linearity of the detector is especially important when making comparisons of the absolute intensity, as it is often the case when using the anomalous scattering effect. Furthermore, when measuring both Bragg diffraction and diffuse scattering in the same scan, the dynamical range of the interesting signal can be many orders of magnitude.

A special card calculates the detector dead time, and depending of the experimental value and a range of acceptable values set by the user, the system change the absorber to increase or decrease the intensity arriving to the detector. The whole operation is automatic, and the controlling program calculates the corrected intensity in real time. There are absorbers of different materials and thickness, in order to cover the whole range of energies used (2.1 – 35 keV).

The following table helps to choose the appropriate absorber material and thickness. The results are also reported in the following graph.

Material Energy (keV) Thickness of the base foil (microns)
Al 7.5-9.5
9-12		 100
200
Mo 17-19.5 100

 

Secondary slits III (Secondary Source)

A pair of uncooled slits clean the beam or act as a secondary source to remove any wavefront modulation caused by the upstream optics. They are step motor driven, equipped with limit switches and an incremental encoder. They are pumped with a 220l/s ion pump. The power supply of the pump is in the Electronics Rack 01. Typical pressure 10-6 mbar.

I0 monitor

The beam traverses a thin kapton foil and the diffused radiation is collected by a photodiode. The kapton foil position is controlled by a pneumatic acturator driver (names kap3).

The current is amplified with a Novelec amplifier operated at variable gain from 107 to 109 and it is injected in a voltage/frequency converter. Then the VME counter card communicates to the work station the counting rate which is read as a counter (Mon2/Mon1).