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/*******************************************************************************
*
* McStas, neutron ray-tracing package
* Copyright 1997-2002, All rights reserved
* Risoe National Laboratory, Roskilde, Denmark
* Institut Laue Langevin, Grenoble, France
*
* Component: SiC
*
* %I
* Written by: <a href="mailto:S.RYCROFT@IRI.TUDELFT.NL">S. Rycroft</a>
* Date: Jan 2000
* Origin: IRI.
*
* SiC layer sample
*
* %D
* SiC layer sample
*
* Example: SiC()
*
* %P
* INPUT PARAMETERS:
*
* xlength: [m] length of SiC plate
* yheight: [m] height of SiC plate
*
* %E
*******************************************************************************/
DEFINE COMPONENT SiC
SETTING PARAMETERS (xlength, yheight)
/* Neutron parameters: (x,y,z,vx,vy,vz,t,sx,sy,sz,p) */
DECLARE
%{
double ScatGrad[85];
double xlength;
double yheight;
%}
INITIALIZE
%{
int i;
for (i = 0; i < 85; ++i)
ScatGrad[i] = 0;
ScatGrad[1]=7.3106e-6;
ScatGrad[81]=2.073e-6-7.3106e-6;
%}
TRACE
%{
double dt, q;
/* Variables added for Rayleigh Appproximation. */
double realZ,imagZ;
double csZ,snZ,Qc,R0;
int i,Z,q_count;
Qc=0.010208;
R0=1.0;
/* First check if neutron has the right direction. */
if(vz != 0.0 && (dt = -z/vz) >= 0)
{
double old_x = x, old_y = y;
x += vx*dt;
y += vy*dt;
/* Now check if neutron intersects mirror. */
if(x >= 0 && x <= xlength && y >= 0 && y <= yheight)
{
z = 0;
t += dt;
q = fabs(2*vz*V2Q);
vz = -vz;
/* Reflectivity (see component Guide).
Changed to calculate from real sample. */
if(q > Qc)
{
realZ = 0;
imagZ = 0;
for (Z = 0; Z < 85; Z++)
{
csZ = cos(-1.*q*Z);
snZ = sin(-1.*q*Z);
realZ = realZ + ScatGrad[Z] * csZ;
imagZ = imagZ + ScatGrad[Z] * snZ;
}
p *=16.*PI*PI*((realZ*realZ)+(imagZ*imagZ))/(q*q*q*q);
}
p *= R0;
SCATTER;
}
else
{
x = old_x;
y = old_y;
}
}
%}
MCDISPLAY
%{
%}
END
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