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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: Pol_Bfield_stop
*
* %I
* Written by: Erik B Knudsen, Peter Christiansen, and Peter Willendrup
* Date: August 2006
* Origin: RISOE
*
* Magnetic field component.
*
* %D
*
* End of magnetic field region defined by the latest preceeding Pol_Bfield component.
*
* The component is concentric. It means that it requires a
*
* // START MAGNETIC FIELD
* COMPONENT msf =
* Pol_Bfield(xw=0.08, yh=0.08, length=0.2, Bx=0, By=-0.678332e-4, Bz=0)
* AT (0, 0, 0) RELATIVE armMSF
*
* // HERE CAN BE OTHER COMPONENTS INSIDE THE MAGNETIC FIELD
*
* // STOP MAGNETIC FIELD
* COMPONENT msfCp = Pol_Bfield_stop()
* AT ("SOMEWHERE") RELATIVE armMSF
*
* In between the two components the propagation routine
* PROP_DT also handles the spin propagation.
* The current algorithm used for spin propagation is:
* SimpleNumMagnetPrecession
* in pol-lib.
* and does not handle gravity.
*
* GRAVITY: NO
* POLARISATION: YES
*
* Example: Pol_Bfield_stop()
*
* %P
* INPUT PARAMETERS:
* geometry: [str] Name of an Object File Format (OFF) or PLY file for complex field-geometry.
* xwidth: [m] Width of opening.
* yheight: [m] Height of opening.
* zdepth: [m] Length of field.
* radius: [m] Radius of field if it is cylindrical or spherical.
*
* %E
****************************************************************************/
DEFINE COMPONENT Pol_Bfield_stop
SETTING PARAMETERS (string geometry="", yheight=0, xwidth=0, zdepth=0, radius=0)
/* Neutron parameters: (x,y,z,vx,vy,vz,t,sx,sy,sz,p) */
SHARE
%{
%include "pol-lib"
%}
DECLARE
%{
int shape;
%}
INITIALIZE
%{
enum shapes {NONE=0, BOX, WINDOW, CYLINDER, SPHERE, ANY};
/*if a start component is given, and no geometry is set, inherent geometry from start comp.*/
if(geometry && strlen(geometry)){
shape=ANY;
}else if(xwidth && yheight && zdepth){
shape=BOX;
}else if (xwidth && yheight && !zdepth){
shape=WINDOW;
}else if(radius && yheight){
shape=CYLINDER;
}else if (radius) {
shape=SPHERE;
}else{
shape=NONE;
}
%}
TRACE
%{
double t0,t1;
int nofield=0;
enum shapes {NONE=0, BOX, WINDOW, CYLINDER, SPHERE, ANY};
/*enter through whatever object we are*/
switch (shape){
case BOX:
box_intersect(&t0,&t1,x,y,z,vx,vy,vz,xwidth,yheight,zdepth);
if (t0>FLT_EPSILON) PROP_DT(t0);/*this is to get a hollow inside the field.*/
else PROP_DT(t1);
break;
case CYLINDER:
cylinder_intersect(&t0,&t1,x,y,z,vx,vy,vz,radius,yheight);/*this is to get a hollow inside the field.*/
if (t0>FLT_EPSILON) PROP_DT(t0);
else PROP_DT(t1);
break;
case WINDOW:
PROP_Z0;
/*terminate neutrons which miss the exit window*/
if (2*x>xwidth || 2*x<-xwidth || 2*y>yheight || 2*y<-yheight){
ABSORB;
}
break;
default:
PROP_Z0;
}
mcmagnet_pop(_particle);
%}
END
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