BL4-2 Biological Small Angle Scattering/Diffraction

Monochromator

The monochromator at the beamline has two interchangeable pairs of liquid nitrogen cooled diffractive elements (a pair of Si(111) crystals and a pair of Mo/B4C multilayers) to select the appropriate energy band for the experiment. They are mounted in the same vacuum chamber and can be interchenged fully remotely

  • the Si(111) crystal is typically used for standard solution and diffraction experiments at the beamline and provides a total flux of approximately 3x1012 ph/s in the full beam (at 500mA SPEAR3 current) with an high energy resolution of ΔE/E ~10-4
  • the Mo/B4C multilayer is used for fast time resolved experiments and provides a total flux of approximately 1x1014 ph/s in the full beam (at 500mA SPEAR3 current) with a energy resolution of  ΔE/E ~2 x

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Monochromotor Schematic  
 
Monochromoter Picture 1		  
 
Monochromoter Picture 2

Schematic of the BL4-2 monochromator. The location of the pairs of diffractive elements inside the vacuum chamber is indicated.

 Picture of the chamber housing the monochromator pairs. The beampath in the Si(111) position is indicated with the red arrow, beam coming from the left. Picture of the inside of the chamber housing the monochromators. The beampath in the Mo/B4C multilayer position is indicated with the green arrow, beam coming from the left.

Reference for the multilayer monochromator: "A wide-bandpass multilayer monochromator for biological small-angle scattering and fiber diffraction studies." H. Tsuruta, S. Brennan, Z.U. Rek, T.C. Irving, W.H. Tompkins, K.O. Hodgson, J. Appl. Cryst. 31, 672-682 (1998).