journal menu
![[Figure 1]](ge5108fig1mag.jpg)
|
|
Figure 1
Experimental setup. (a)–(c) MAGIK reflectometer operation. (a) A λ = 5 Å beam is selected from a polychromatic source in the neutron guide with a triple-blade monochromator (Δλ/λ ≃ 0.9%). With the sample rotated to an angle θ relative to the incident beam, specular reflection occurs at a detector rotation angle Δ. The collimation determines the width of the beam, shown as dashed lines. In this diagram, which is not to scale, the asymmetry in the beam is exaggerated by the oversized sample and large reflection angles. Background subtraction is performed by interpolation between intensities measured with the detector rotated to either side of the specular ridge. (b), (c) Implementation of energy analysis on MAGIK using an HOPG analyzer crystal. (b) When the analyzer is `in', the HOPG analyzer is rotated to θanalyzer and the helium tube to 2θanalyzer, selecting a wavelength λf = 2dHOPGsin(θanalyzer). (c) When the analyzer is `out', θanalyzer = 90° and the helium tube is at 0°, i.e. in the path of scattered neutrons of all wavelengths. (d) The CANDOR reflectometer operates similarly to MAGIK but effectively acts as 54 independent energy-analyzed reflectometers. The physical length of the CANDOR reflectometer is also approximately 2.5 times that of MAGIK. (e) A schematic diagram of the CANDOR detector. Individual HOPG blades diffract neutrons of the appropriate wavelength into scintillation detectors and are colored according to the `temperature' of the selected neutrons. (f) The geometry of the flow cell. A thin liquid reservoir is created in the space between two silicon wafers separated by a thin Teflon gasket. The presample slit openings are proportional to sin(θ) so the beam footprint on the sample remains constant. (g) The thickness D of the liquid reservoir is determined by measuring the angle-dependent transmission of neutrons through an H2O-filled reservoir. Error bars represent a 68% confidence interval derived from the Poisson-distributed uncertainty in the neutron counts. (h) The nominal crystal orientation of the silicon wafer. The flat denotes the [220] direction and is rotated at an angle γ relative to the beam direction. |
![[Figure 1]](ge5108fig1.jpg)
 | JOURNAL OF APPLIED CRYSTALLOGRAPHY |
ISSN: 1600-5767
