Component Manual for the Neutron Ray-Tracing Package McStas, version 3.8.6

14.23  The Conics_PP McStas Component

Release: McStas 2.7 Date: September 2021

Parabolid-Parabolid shells for Wolter optic

Identification

Description

Implements a set of nshells Wolter I Paraboloid/Parabolid pairs using conics.h from ConicTracer.

The component has two distinct modes of specifying the geometry: a) Via the radii vector, parametrized from largest to smallest radius with a length of ’nshells’

b) By specifying radii rmax and rmin, between which a quadratic law distributes ’nshells’ surfaces.

The mirrors are assumed to be touching at the mid-optic plane, i.e. there is no gap between primary and secondary mirror. By definition the ratio between primary and secondary mirror glancing angles is 1/3. At present a single m-value is used for all mirrors.

Input parameters

Parameters in boldface are required; the others are optional.

Name

Unit

Description

Default

rmin

m

Midoptic plane radius of innermost mirror pair.

0.0031416

rmax

m

Midoptic plane radius of outermost mirror pair.

0.05236

focal_length_u

m

Focal length of upstream mirror.

10.070

focal_length_d

m

Focal length of downstream mirror.

10.070

lp1

m

Upstream paraboloid mirror length.

0.84

lp2

m

Downstream paraboloid mirror length.

0.84

nshells

1

Number of nested shells to expect

4

m

1

Critical angle of mirrors as multiples of Ni.

1

mirr_thick

m

Thickness of mirror shell surfaces - NOT YET IMPLEMENTED

0

disk

Flag. If nonzero, insert a disk to block the central area within the innermost mirror.

1

radii

m

Optional vector of radii (length should match nshells)

NULL

R0

1

Reflectivity at Low angles for reflectivity curve approximation

0.99

Qc

Å\(^{-1}\)

Critical scattering vector

0.021

W

Å\(^{-1}\)

Width of supermirror cut-off

0.003

alpha

Å

Slope of reflectivity for reflectivity curve approximation

6.07

transmit

1

Fraction of statistics to assign to transmitted beam - NOT YET IMPLEMENTED

0

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