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

7.9  The Pol_guide_vmirror McStas Component

Polarising guide with nvs x 2 supermirrors sitting in v-shapes inside, upgraded from original single V-cavity.

Identification

Description

Models a rectangular guide with entrance centered on the Z axis and with nvs x two supermirrors sitting in v-shapes inside. The entrance lies in the X-Y plane. Draws a true depiction of the guide with mirrors, 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)

The reflectivity parameters can be 1. double pointer initializations with 5 parameters (e.g. {R0, Qc, alpha, m, W} AND inputType=0), or 2. double pointer initializations with 6 parameters (e.g. {R0, Qc, alpha, m, W, beta} AND inputType=0), or 3. table names (e.g."supermirror_m2.rfl" AND inputType=1), or 4. individually assigned values (e.g. rR0=1.0, rQc=0.0217, ... etc AND inputType=2). NB! This might cause warnings by the compiler that can be ignored. Note that the reflectivity functions that use with values and those that use tables are different.

GRAVITY: YES

%BUGS No absorption by mirror.

Input parameters

Parameters in boldface are required; the others are optional.

Name

Unit

Description

Default

nvs

1

Number of V-cavities across width of guide

1

xwidth

m

Width at the guide entry

0.1

yheight

m

Height at the guide entry

0.1

length

m

length of guide

0.5

rR0

1

Cavity wall reflectivity below critical scattering vector, use with inputType = 2

1.0

rQc

Å\(^{-1}\)

Cavity wall reflectivity critical scattering vector, use natural Ni (m=1 definition) value of 0.0217, use with inputType = 2

0.0217

ralpha

Å

Cavity wall slope of reflectivity, use with inputType = 2

6.5

rmSM

1

Cavity wall m-value of material. Zero means completely absorbing. Use with inputType = 2

2

rW

Å\(^{-1}\)

Cavity wall width of reflectivity cut-off, use with inputType = 2

0.00157

rbeta

Å\(^{2}\)

Cavity wall curvature of reflectivity, use with inputType = 2

80

rUpR0

1

Mirror spin up reflectivity below critical scattering vector, use with inputType = 2

1.0

rUpQc

Å\(^{-1}\)

Mirror spin up reflectivity critical scattering vector, use natural Ni (m=1 definition) value of 0.0217, use with inputType = 2

0.0217

rUpalpha

Å

Mirror spin up slope of reflectivity, use with inputType = 2

2.47

rUpmSM

1

Mirror spin up m-value of material. Zero means completely absorbing. Use with inputType = 2

4

rUpW

Å\(^{-1}\)

Mirror spin up width of reflectivity cut-off, use with inputType = 2

0.0014

rUpbeta

Å\(^{2}\)

Mirror spin up curvature of reflectivity, use with inputType = 2

0

rDownR0

1

Mirror spin down reflectivity below critical scattering vector, use with inputType = 2

1.0

rDownQc

Å\(^{-1}\)

Mirror spin down reflectivity critical scattering vector, use natural Ni (m=1 definition) value of 0.0217, use with inputType = 2

0.0217

rDownalpha

Å

Mirror spin down slope of reflectivity, use with inputType = 2

1

rDownmSM

1

Mirror spin down m-value of material. Zero means completely absorbing. Use with inputType = 2

0.65

rDownW

Å\(^{-1}\)

Mirror spin down width of reflectivity cut-off, use with inputType = 2

0.003

rDownbeta

Å\(^{2}\)

Mirror spin down curvature of reflectivity, use with inputType = 2

0

debug

1

if debug > 0 print out some internal runtime parameters

0

allow_inside_start

1

Allow neutron to start inside cavity (no propagation to entry plane)

0

rPar

1

Cavity wall parameters array for rFunc, use with inputType = 0

{1.0, 0.0217, 6.5, 2, 0.00157, 80}

rUpPar

1

Mirror Parameters array for rUpFunc, use with inputType = 0

{1.0, 0.0217, 2.47, 4, 0.0014}

rDownPar

1

Mirror Parameters for rDownFunc, use with inputType = 0

{1.0, 0.0217, 1, 0.65, 0.003}

rParFile

Cavity wall parameters filename for rFunc, use with inputType = 1

""

rUpParFile

Mirror Parameters filename for rUpFunc, use with inputType = 1

""

rDownParFile

Mirror Parameters filename for rDownFunc, use with inputType = 1

""

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