7.6  The Pol_mirror McStas Component

Polarising mirror.

Identification

• Author: Peter Christiansen

• Origin: RISOE

• Date: July 2006

Description

This component models a rectangular infinitely thin mirror. For an unrotated component, the mirror surface lies in the Y-Z plane (ie. parallel to the beam). It relies on similar physics as the Monochromator_pol. The reflectivity function (see e.g. share/ref-lib for examples) and parameters are passed to this component to give a bigger freedom. The up direction is hardcoded to be along the y-axis (0, 1, 0) IMPORTANT: At present the component only works correctly for polarization along the up/down direction and for completely unpolarized beams, i.e. sx=sy=sz=0 for all rays.

For now we assume: P(Transmit|Q) = 1 - P(Reflect|Q) i.e. NO ABSORPTION!

The component can both reflect and transmit neutrons with a respective proportion depending on the p_reflect parameter: p_reflect=-1 Reflect and transmit (proportions given from reflectivity) [default] p_reflect=1 Only handle reflected events p_reflect=0 Only handle transmitted events (reduce weight) p_reflect=0-1 Both transmit and reflect with fixed statistics proportions

The parameters can either be double pointer initializations (e.g. {R0, Qc, alpha, m, W}) or table names (e.g."supermirror_m2.rfl" AND useTables=1). NB! This might cause warnings by the compiler that can be ignored.

Examples: Reflection function parametrization Pol_mirror(zwidth = 0.40, yheight = 0.40, rUpFunc=StdReflecFunc, rUpPar={1.0, 0.0219, 6.07, 2.0, 0.003})

Table function Pol_mirror(zwidth = 0.40, yheight = 0.40, rUpFunc=TableReflecFunc, rUpPar="supermirror_m2.rfl", rDownFunc=TableReflecFunc, rDownPar="supermirror_m3.rfl", useTables=1)

See also the example instrument Test_Pol_Mirror (under tests).

GRAVITY: YES

%BUGS NO ABSORPTION

Input parameters

Parameters in boldface are required; the others are optional.

Links

• Component source code found in file Pol_mirror.comp.