/*******************************************************************************
*
* McStas, neutron ray-tracing package
*         Copyright (C) 1997-2011, All rights reserved
*         Risoe National Laboratory, Roskilde, Denmark
*         Institut Laue Langevin, Grenoble, Fance
*
* Component: SANS_Spheres_Abs
*
* %I
* Written by: Wim Bouwman, Delft University of Technology
* Date:       Aug 2012
* Origin:     
* Version:    $Revision: 1.0 $
* Release:    McStas 1.12c
* Original file: SANS_AnySamp
* Written by: Henrich Frielinghaus
* Date:       Sept 2004
* Origin:     FZ-Juelich/FRJ-2/IFF/KWS-2
* Version:    $Revision: 1.5 $
*
* Solid dilute monodisperse spheres sample with transmitted beam for Small Angle Neutron Scattering.
*
* %D
* Sample for Small Angle Neutron Scattering.
* Modified from the Any Sample model.
* Normalization of scattering is done in INITIALIZE.
* Some elements of Sans_spheres have been re-used
*
* Some remarks:
* Scattering function should be a defined the same way in INITIALIZE and TRACE sections
* There exist maybe better library functions for the integral.
*
* Transmitted paths set to 50% of all paths to be optimised for SESANS. In this simulation method paths are
* well distributed among transmission and scattering (equally in Q-space).
*
* Sample components leave the units of flux for the probability
* of the individual paths. That is more consitent than the
* Sans_spheres routine. Furthermore one can simulate the
* transmitted beam. This allows to determine the needed size of
* the beam stop. Absorption is included to
* these sample-components. 
*
* Example: SANS_Spheres_Abs(R=100, Phi=1e-3, Delta_rho=0.6, sigma_a = 50, qmax=0.03, xwidth=0.01, yheight=0.01, zthick=0.001)
*
* %P
*
* INPUT PARAMETERS
*
* R	     : Radius of scattering hard spheres (AA)
* Phi	     : Particle volume fraction (1)
* Delta_rho  : Excess scattering length density (fm/AA^3)
* sigma_a:   Absorption cross section density at 2200 m/s (m^-1)
* qmax (AA-1): Maximum scattering vector (typically 10/R to observe the 3rd ring)
* xwidth  (m): horiz. dimension of sample, as a width (m)
* yheight (m): vert.. dimension of sample, as a height (m)
* zthick  (m): thickness of sample (m)
*
* %Link
* Sans_spheres component
* SANS_AnySamp component
*
* %E
*******************************************************************************/

DEFINE COMPONENT SANS_Liposomes_Abs

SETTING PARAMETERS (R=100, dR=0.0,Phi=1e-3, Delta_rho=0.6, sigma_a=0.50, qmax=0.03, xwidth=0.01, yheight=0.01, zthick=0.001, dbilayer=35)

DECLARE
%{
  double my_a_v;
  double isq;
  double Ri;
  double fi;
%}

INITIALIZE
%{
    if (!xwidth || !yheight || !zthick) {
  exit(fprintf(stderr,"SANS_AnySamp: %s:   sample has no volume (zero dimensions)\n", NAME_CURRENT_COMP));
    }

  int    iqmax=30000,iq=iqmax;    // number of intervals
  double q,sq,f;

  isq = 0.0;           // integral = 0

  while (iq > 1)       // start integrating with low intensities at large q
  {                               // MODIFIY HERE
  q  = (iq-0.5)*qmax/iqmax;       // q always slightly larger than 0
  if(Ri<=0)
    fi = 0;
else
    fi = 3*(sin(q*Ri) - q*Ri*cos(q*Ri))/(q*Ri*q*Ri*q*Ri);
    
  sq = fi*fi;	                  // define this function in INITIALIZE and TRACE part
  sq*= q;
  isq+= sq;
  --iq;
  }

  isq*=qmax/iqmax;
  my_a_v = sigma_a*2200*100;           /* Is not yet divided by v. 100: Convert barns -> fm^2 */

%}

TRACE
%{
  double a,q,qm,sq,f;
  double Vi,Vo;
  double RiTrace,Ro;
  double fiTrace, fo;
  double transsim=0.5;                  // portion of paths for transmission, ~ 0.03 for SANS, 0.5 for SESANS
  double my_s_pre;
  double q_v;

  double transmr, t0, t1, v, l_full, l, dt, d_phi, theta;
  double axis_x, axis_y, axis_z;
  double arg, tmp_vx, tmp_vy, tmp_vz, vout_x, vout_y, vout_z;
  char   intersect=0;

  RiTrace=Ri;
  fiTrace=fi;
  
  Ro=R+randnorm()*dR;
  RiTrace = Ro-dbilayer; /*  Calculate inner radius of liposphere */
  if(dbilayer==R)
	  RiTrace=0; /*  Treat sample as solid spheres */
  Vi = 4/3*PI*RiTrace*RiTrace*RiTrace;
  Vo = 4/3*PI*Ro*Ro*Ro;
  my_s_pre = Phi * (Vo-Vi) * Delta_rho*Delta_rho;

  intersect = box_intersect(&t0, &t1, x, y, z, vx, vy, vz, xwidth, yheight, zthick);
  if(intersect)
  {
    if(t0 < 0) ABSORB;                   /* Neutron enters at t=t0. */

    v = sqrt(vx*vx + vy*vy + vz*vz);
    /* amount of scattering is described by \lambda^2 zthick Delta_rho^2 phi 3/2 R */
    /* for example J. Schelten, W. Schmatz: J. Appl. Crystallogr. 13, 385 (1980) */
    /* units perfectly cancel each other \AA^2 m fm^2 \AA^-6 \AA = 1 */
    transmr = 1.0 - 4.0*PI*PI/V2K/V2K/v/v*zthick*Delta_rho*Delta_rho*Phi*1.5*R;       /* transmission for single scattering */
/*  if (transmr<1e-10) transmr = 1e-10; */
/*  if (transmr>0.99 ) transmr = 0.99;  */

    l_full = v * (t1 - t0);              /* Length of full path through sample */
    transmr = exp(log(transmr)*l_full/zthick);  /* real transmission */

    dt = rand01()*(t1 - t0) + t0;        /* Time of scattering */
    PROP_DT(dt);                         /* Point of scattering */
    l = v*dt;                            /* Penetration in sample */

    qm = qmax;                           // adjust maximal q
    if (qm > 2.0*v/K2V) qm = 2.0*v/K2V;  // should not be totally wrong
    q = sqrt(rand01())*qm;               // otherwise normalization with isq is wrong

    q_v = q*K2V;                         /* scattering possible ??? */
    arg = q_v/(2.0*v);

    if(rand01()>transsim)
    {
      //  f = 3 * (sin(q*R) - q*R*cos(q*R))/(q*R*q*R*q*R);

    fo = 3*(sin(q*Ro) - q*Ro*cos(q*Ro))/(q*Ro*q*Ro*q*Ro);
    
if(RiTrace<=0)
    fiTrace = 0;
else
    fiTrace = 3*(sin(q*RiTrace) - q*RiTrace*cos(q*RiTrace))/(q*RiTrace*q*RiTrace*q*RiTrace);
    
    f= (Vo*fo-Vi*fiTrace)/(Vo-Vi);

    sq = f*f;	                  // define this function in INITIALIZE and TRACE part

    p*= sq*(qmax*qmax*0.5)*(1.0-transmr)/(1.0-transsim)/isq;

    theta = asin(arg);                   /* Bragg scattering law */
    d_phi = 2*PI*rand01();

    vec_prod(axis_x, axis_y, axis_z, vx, vy, vz, 0, 1, 0);
    rotate(tmp_vx, tmp_vy, tmp_vz, vx, vy, vz, 2*theta, axis_x, axis_y, axis_z);
    rotate(vout_x, vout_y, vout_z, tmp_vx, tmp_vy, tmp_vz, d_phi, vx, vy, vz);

    vx = vout_x;
    vy = vout_y;
    vz = vout_z;

    if(!box_intersect(&t0, &t1, x, y, z, vx, vy, vz, xwidth, yheight, zthick))    fprintf(stderr, "SANS_AnySamp: FATAL ERROR: Did not hit box from inside.\n");
    }
    else
    {
    p*= transmr / transsim;
    }
    p *= exp(-my_a_v*(l_full)/v);
    SCATTER;
  }
%}

MCDISPLAY
%{
  double radius = 0;
  double h = 0;
  magnify("xyz");
  {
    double xmin = -0.5*xwidth;
    double xmax =  0.5*xwidth;
    double ymin = -0.5*yheight;
    double ymax =  0.5*yheight;
    double zmin = -0.5*zthick;
    double zmax =  0.5*zthick;
    multiline(5, xmin, ymin, zmin,
                 xmax, ymin, zmin,
                 xmax, ymax, zmin,
                 xmin, ymax, zmin,
                 xmin, ymin, zmin);
    multiline(5, xmin, ymin, zmax,
                 xmax, ymin, zmax,
                 xmax, ymax, zmax,
                 xmin, ymax, zmax,
                 xmin, ymin, zmax);
    line(xmin, ymin, zmin, xmin, ymin, zmax);
    line(xmax, ymin, zmin, xmax, ymin, zmax);
    line(xmin, ymax, zmin, xmin, ymax, zmax);
    line(xmax, ymax, zmin, xmax, ymax, zmax);
  }

%}
END

