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/*****************************************************************************
*
* McStas, neutron ray-tracing package
* Copyright 1997-2006, All rights reserved
* Risoe National Laboratory, Roskilde, Denmark
* Institut Laue Langevin, Grenoble, France
*
* Component: PolAnalyser_ideal
*
* %I
* Written by: Erik Knudsen
* Date: June 2010
* Origin: Risoe
*
* (Unphysical) ideal analyzer.
*
* %D
*
* This is an ideal model of a polarization analyser device. Given a polarization vector
* it "lets through" a scaled neutron weight. An imperfect analyzer could be modelled by an
* analysis vector M with |M|<1.
*
* Example: PolAnalyser_ideal(mx=0, my=1, mz=0)
*
* %P
* INPUT PARAMETERS:
*
* mx: [1] X-component of polarisation analysis vector -1<mx<1
* my: [1] Y-component of polarisation analysis vector -1<my<1
* mz: [1] Z-component of polarisation analysis vector -1<mz<1
*
* CALCULATED PARAMETERS:
*
* %E
*******************************************************************************/
DEFINE COMPONENT PolAnalyser_ideal
SETTING PARAMETERS (mx=0, my=0, mz=0)
DECLARE
%{
%}
INITIALIZE
%{
if (mx==0 && my==0 && mz==0) {
printf("PolAnalyser_ideal: %s: NULL vector defined!\n"
"ERROR (mx, my, mz)=(0,0,0). Exiting",
NAME_CURRENT_COMP);
exit(1);
}
if ((mx*mx + my*my + mz*mz) > 1) {
printf("PolAnalyser_ideal: %s: Polarisation analysis vector (mx, my, mz) is unphysical!\n"
"ERROR mx*mx + my*my + mz*mz > 1. Exiting....",
NAME_CURRENT_COMP);
exit(1);
}
NORM(mx,my,mz);
%}
TRACE
%{
double prob_up;
prob_up=(1+scalar_prod(sx,sy,sz,mx,my,mz))/2.0;
if (prob_up>0) {
/*adjust weight accordingly (i.e. monte carlo choice with prob. 1)*/
p*=prob_up;
sx=mx;sy=my;sz=mz;
SCATTER;
} else {
ABSORB;
}
%}
MCDISPLAY
%{
/* A bit ugly; hard-coded dimensions. */
line(0,0,0,0.2,0,0);
line(0,0,0,0,0.2,0);
line(0,0,0,0,0,0.2);
line(0,0,0,0.2*mx,0.2*my,0.2*mz);
/*draw the arrowhead*/
double cos2=cos(2*DEG2RAD);
double sin2=sin(2*DEG2RAD);
multiline(4,0.18*(mx*cos2+my*sin2),0.18*(-mx*sin2+my*cos2),0.18*mz,
0.18*(mx*cos2+mz*sin2),0.18*my,0.18*(-mx*sin2+mz*cos2),
0.18*mx,0.18*(my*cos2+mz*sin2),0.18*(-my*sin2+mz*cos2),
0.18*(mx*cos2+my*sin2),0.18*(-mx*sin2+my*cos2),0.18*mz);
line(0.2*mx,0.2*my,0.2*mz,0.18*(mx*cos2+my*sin2),0.18*(-mx*sin2+my*cos2),0.18*mx);
line(0.2*mx,0.2*my,0.2*mz,0.18*(mx*cos2+mz*sin2),0.18*my,0.18*(-mx*sin2+mz*cos2));
line(0.2*mx,0.2*my,0.2*mz,0.18*mx,0.18*(my*cos2+mz*sin2),0.18*(-my*sin2+mz*cos2));
%}
END
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