The Advanced Photon Source
a U.S. Department of Energy Office of Science User Facility

Low Energy Diffraction

Diffraction at low energies requires in-vacuum beam path and reduction of absorbing windows as much as possible. The beam path at 4-ID-D is optimized for this kind of experiments by using an in-vacuum chamber for the closed cycle cryostat which connects to both, the beam path upstream and the one on detector arm. In case polarization analysis is desired, an in-vacuum polarization analyzer is available with full flexibility to move between  ' and  ' geometry. In vacuum sample chamber has limited range in chi movement (+/- 10 degrees). In case higher flexibility is needed, Beryllium domes have to be used at the expense of significant intensity due to higher photon absorption.

Parameters

  • Energy range: 2.7 - 5 keV
  • Temperature range: 8 - 300 K
  • Incident polarization:
    • variable linear (sigma, pi) (E > 3.2 keV)
    • linear sigma (E < 3.2 keV)
    • circular left and right
  • Detector: APD or Cyberstar
  • Polarization analysis: flexible (sigma to pi), in-vacuum

Polarization analysis

Available Analyzers Energy (keV) Absorption edges
Graphite (002) 2.61 Mo (L2)
Si (111) 2.80 Ru (L3)
GdMnO3 (020) 2.98 Ru (L2)
Au (111) 3.75 U (M4,M5)
Graphite (004) 5.22 V (K)

 

 

 

 

 

Diffractometer with cryostat, full in-vacuum shroud1 and polarization analyzer. Inserts: Sample holder for in-vacuum setup and Be heat shield.

1On loan from DESY, Hamburg, Germany