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/*******************************************************************************
*
* McXtrace, x-ray tracing package
* Copyright, All rights reserved
* DTU Physics, Kgs. Lyngby, Denmark
* Synchrotron SOLEIL, Saint-Aubin, France
*
* Component: Bragg_crystal_simple
*
* %Identification
*
* Written by: Jose I. Robledo
* Date: February 2016
* Version: $Revision$
* Release: McXtrace 1.2
* Origin: FaMAF - UNC, Argentina
*
* Perfect Bragg reflecting slab
*
* %Description
*
* Rectangle of matter perfectly reflecting the incident X-ray beam
* that fulfills Bragg's law for a set of scattering vectors in the
* vicinity of the theoretical Q given a d-spacing.
* The rectangle is in the x-y plane.
*
* Example: Bragg_crystal_simple( yheight=0.05, xwidth=0.02, DM=3.1356, err_Q= 0.000075, r0=1.0)
*
* %Parameters
* Input parameters:
* xwidth: [m] Width in the x direction
* yheight: [m] Height in the y direction
* r0: [ ] Maximum reflectivity
* DM: [AA⁻1] d-spacing of the crystal
* err_Q: [ ] dQ/Q relative error of the modulus of Q vector. Approximates the Darwin width of the crystal.
*
* %End
*******************************************************************************/
DEFINE COMPONENT Bragg_crystal_simple
SETTING PARAMETERS (xmin=1.0,xmax=1.0,ymin=1.0,ymax=1.0,xwidth=0.0,yheight=0.0,r0=1,DM=0,err_Q=0.0001)
/* X-ray parameters: (x,y,z,kx,ky,kz,phi,t,Ex,Ey,Ez,p) */
DECLARE %{
double Q;
double dQ;
%}
INITIALIZE %{
if (DM != 0) {
Q=2*PI/DM; dQ=Q*err_Q;
}else{
fprintf(stderr,"WARNING: Bragg_crystal_simple (%s) d-spacing==0, crystal will ABSORB all X-rays.\n",NAME_CURRENT_COMP);
}
if (xwidth>0) { xmax = xwidth/2; xmin=-xmax; }
if (yheight>0) { ymax = yheight/2; ymin=-ymax; }
if (xmin==xmax || ymin==ymax)
exit(fprintf(stderr, "Bragg_crystal_simple (%s) : Surface is null (xmin,xmax,ymin,ymax)\n", NAME_CURRENT_COMP));
%}
TRACE
%{
double k,e,theta_bragg;
k=sqrt(kx*kx+ky*ky+kz*kz);
e=K2E*k*1E-3;
theta_bragg=atan(kz/ky);
PROP_Z0; //MOVING TOWARDS THE CRYSTAL.
if (inside_rectangle(x, y, xwidth, yheight))
{if (Q>(2*k*sin(theta_bragg)-dQ) && Q<(2*k*sin(theta_bragg)+dQ))
{kz=-kz;
SCATTER;
}else{
ABSORB;
}
}
%}
MCDISPLAY
%{
/* A bit ugly; hard-coded dimensions. */
magnify("");
line(-xwidth/2,-yheight/2,0,xwidth/2,-yheight/2,0);
line(-xwidth/2,yheight/2,0,xwidth/2,yheight/2,0);
line(-xwidth/2,-yheight/2,0,-xwidth/2,yheight/2,0);
line(xwidth/2,-yheight/2,0,xwidth/2,yheight/2,0);
%}
END
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