/*******************************************************************************
*
* McStas, neutron ray-tracing package
*         Copyright 1997-2002, All rights reserved
*         Risoe National Laboratory, Roskilde, Denmark
*         Institut Laue Langevin, Grenoble, France
*
* Written by: Erik B Knudsen
* Date: May 2017
* Version: $Revision$
* Release: McStas 2.4
* Origin: DTU Physics
*
* Component: Pol_RFSF_ideal
*
*
* %I
*
* Ideal model of a spin flipper
*
* %D
* This component simply mirrors the polarization vector of the neutron
* ray in the plane through (0,0,0) with normal nx,ny,nz.
* The flipper is surrounded by a perfectly absorbing box. Neutron rays not hitting
* the box are left untouched.
*
* %P
* Input parameters:
* nx:    [ ] x-component of the normal vector of the flipping plane.
* ny:    [ ] y-component of the normal vector of the flipping plane.
* nz:    [ ] z-component of the normal vector of the flipping plane.
* xwidth: [m] width of the spin flipper.
* yheight: [m] height of the spin flipper.
* zdepth: [m] length of the spin flipper.
*
*
* %E
*******************************************************************************/

DEFINE COMPONENT Pol_SF_ideal

SETTING PARAMETERS (nx=0, ny=1, nz=0, xwidth=0.1, yheight=0.1, zdepth=0.1)

/* Neutron parameters: (x,y,z,vx,vy,vz,t,sx,sy,sz,p) */
TRACE
%{
    int hit;
    double t0,t1;
    hit=box_intersect(&t0,&t1, x,y,z,vx,vy,vz, xwidth,yheight,zdepth);
    if(hit){
        PROP_DT(t0);
        if(fabs(z- -zdepth*0.5)>DBL_EPSILON){
            /*neutron must have hit the side walls*/
            ABSORB;
        }
        /*move to center of box and flip*/
        PROP_Z0;
        SCATTER;
        double s=scalar_prod(sx,sy,sz,nx,ny,nz);
        if (s!=0){
            sx-=2*s*nx;
            sy-=2*s*ny;
            sz-=2*s*nz;
        }
        PROP_DT((t1-t0)/2);/*propagate the remaining distance to the box exit*/
        if(fabs(z-zdepth*0.5)>DBL_EPSILON){
            ABSORB;
        }
    }


%}

MCDISPLAY
%{
  double dx=xwidth/16;
  double dy=yheight/8;
  
  box(0,0,0,xwidth,yheight,zdepth,0, 0, 1, 0);
  
  line(dx,-dy,0,dx,-dy+yheight/2.0,0);
  line(-dx,dy,0,-dx,dy-yheight/2.0,0);
  line(dx,-dy+yheight/2.0,0, dx+xwidth/16,-dy+yheight-yheight/16,0);
  line(dx,-dy+yheight/2.0,0, dx-xwidth/16,-dy+yheight-yheight/16,0);
  
  line(-dx,dy-yheight/2.0,0, -dx+xwidth/16,dy-yheight+yheight/16,0);
  line(-dx,dy-yheight/2.0,0, -dx-xwidth/16,dy-yheight+yheight/16,0);

%}

END
