7.8  The Pol_guide_mirror McStas Component

Polarising guide with a supermirror along its diagonal.

Identification

• Author: Erik B Knudsen

• Origin: DTU Physics

• Date: July 2018

Description

Based on Pol_guide_vmirror by P. Christiansen. Models a rectangular guide with entrance centered on the Z axis and with one supermirror sitting on the diagonal inside. The entrance lies in the X-Y plane. Draws a true depiction of the guide with mirror and trajectories. The polarisation is handled similar to in Monochromator_pol. The reflec functions are handled similar to Pol_mirror. The up direction is hardcoded to be along the y-axis (0, 1, 0)

Note that this component can also be used as a frame overlap-mirror if the up and down reflectivities are set equal. In this case the wall reflectivity (rPar) should probably be set to 0.

Reflectivity values can either come from datafiles or from sets of parameters to the standard analytic reflectivity function commonly used for neutron guides: R=R0; q<qc, R=(1-tanh((q-m qc)/W))(1-alpha(q-qc)). If a filename is specified for e.g. rData the datafile table overrides the analytic function.

GRAVITY: YES

%BUGS No absorption by mirror. The reflectivity parameters must be given as literal constants. Using variables will result in undefined behaviour.

Input parameters

Parameters in boldface are required; the others are optional.

Links

• Component source code found in file Pol_guide_mirror.comp.