/*******************************************************************************
*
* McStas, neutron ray-tracing package
*         Copyright 1997-2002, All rights reserved
*         Risoe National Laboratory, Roskilde, Denmark
*         Institut Laue Langevin, Grenoble, France
*
* Component: Tunneling_sample
*
* %I
* Written by: Kim Lefmann
* Date: 10.05.07
* Origin: Risoe
*
* A Double-cylinder shaped all-incoherent scatterer
* with elastic, quasielastic (Lorentzian), and tunneling (sharp)
* components.
*
* %D
* A Double-cylinder shaped all-incoherent scatterer
* with both elastic, quasielastic (Lorentzian), and tunneling (sharp)
* components. No multiple scattering. Absorbtion included.
* The shape of the sample may be a box with dimensions xwidth, yheight, zdepth.
* The area to scatter to is a disk of radius 'focus_r' situated at the target.
* This target area may also be rectangular if specified focus_xw and focus_yh
* or focus_aw and focus_ah, respectively in meters and degrees.
* The target itself is either situated according to given coordinates (x,y,z),
* or defined with the relative target_index of the component to focus
* to (next is +1).
* This target position will be set to its AT position. When targeting to
* centered components, such as spheres or cylinders, define an Arm component
* where to focus to.
*
* The outgoing polarization is calculated as for nuclear spin incoherence:
*   P' = 1/3*P-2/3P = -1/3P
* As above multiple scattering is ignored .
*
* Example: Tunneling_sample(thickness=0.001,radius=0.01,yheight=0.02,focus_r=0.035,
*           target_index=1)
*
* %P
* INPUT PARAMETERS:
* radius: [m]        Outer radius of sample in (x,z) plane
* yheight: [m]       vert.  dimension of sample, as a height
* thickness: [m]     Thickness of cylindrical sample in (x,z) plane
* focus_r: [m]       Radius of disk containing target. Use 0 for full space
* target_index: [1]  relative index of component to focus at, e.g. next is +1
* xwidth:   horiz. dimension of sample, as a width [m]
* zdepth:   depth of sample [m]
* focus_xw: horiz. dimension of a rectangular area [m]
* focus_yh: vert.  dimension of a rectangular area [m]
* focus_aw: horiz. angular dimension of a rectangular area [deg]
* focus_ah: vert.  angular dimension of a rectangular area [deg]
* sigma_abs:Absorbtion cross section pr. unit cell [barns]
* sigma_inc:Total incoherent scattering cross section pr. unit cell [barns]
* Vc:       Unit cell volume [AA^3]
* p_interact: MC Probability for scattering the ray; otherwise transmit [1]
* f_QE:     Fraction of quasielastic scattering [1]
* f_tun:    Fraction of tunneling scattering (f_QE+f_tun < 1) [1]
* gamma:    Lorentzian width of quasielastic broadening (HWHM) [meV]
* E_tun:    Tunneling energy [meV]
* target_x: X-position of target to focus at [m]
* target_y: Y-position of target to focus at [m]
* target_z: Z-position of target to focus at [m]
*
* Variables calculated in the component
*
* V_my_s: Attenuation factor due to scattering [m^-1]
* V_my_a: Attenuation factor due to absorbtion [m^-1]
*
* %L
* <A HREF="http://neutron.risoe.dk/mcstas/components/tests/v_sample/">Test
* results</A> (not up-to-date).
*
* %E
*******************************************************************************/

DEFINE COMPONENT Tunneling_sample

SETTING PARAMETERS (thickness=0, radius=0.01, focus_r = 0,
p_interact = 1, f_QE=0, f_tun=0, gamma=0, E_tun=0,
target_x = 0, target_y = 0, target_z = 0.235, focus_xw=0, focus_yh=0,
focus_aw=0, focus_ah=0, xwidth=0, yheight=0.05, zdepth=0, sigma_abs=5.08, sigma_inc=4.935, Vc=13.827, int target_index=0)

/* Neutron parameters: (x,y,z,vx,vy,vz,t,sx,sy,sz,p) */

SHARE
%{
struct StructVarsV
{
double sigma_a; /* Absorption cross section per atom (barns) */
    double sigma_i; /* Incoherent scattering cross section per atom (barns) */
    double rho;     /* Density of atoms (AA-3) */
    double my_s;
    double my_a_v;
    char   isrect;      /* true when sample is a box */
    double distance;    /* when non zero, gives rect target distance */
    double aw,ah;       /* rectangular angular dimensions */
    double xw,yh;       /* rectangular metrical dimensions */
    double tx,ty,tz;    /* target coords */
  };
%}

DECLARE
%{
  struct StructVarsV VarsV;
  double ftun;
  double fQE;
%}

INITIALIZE
%{
  if (!xwidth || !yheight || !zdepth) /* Cannot define a rectangle */
    if (!radius || !yheight)              /* Cannot define a cylinder either */
      exit(fprintf(stderr,"V_sample: %s: sample has no volume (zero dimensions)\n", NAME_CURRENT_COMP));
    else                              /* It is a cylinder */
      VarsV.isrect=0;
  else                                /* It is a rectangle */
    VarsV.isrect=1;

  VarsV.sigma_a=sigma_abs;
  VarsV.sigma_i=sigma_inc;
  VarsV.rho = (1/Vc);
  VarsV.my_s=(VarsV.rho * 100 * VarsV.sigma_i);
  VarsV.my_a_v=(VarsV.rho * 100 * VarsV.sigma_a);

  /* now compute target coords if a component index is supplied */
  VarsV.tx= VarsV.ty=VarsV.tz=0;
  if (target_index)
  {
    Coords ToTarget;
    ToTarget = coords_sub(POS_A_COMP_INDEX(INDEX_CURRENT_COMP+target_index),POS_A_CURRENT_COMP);
    ToTarget = rot_apply(ROT_A_CURRENT_COMP, ToTarget);
    coords_get(ToTarget, &VarsV.tx, &VarsV.ty, &VarsV.tz);
  }
  else
  { VarsV.tx = target_x; VarsV.ty = target_y; VarsV.tz = target_z; }

  if (!(VarsV.tx || VarsV.ty || VarsV.tz))
    printf("Tunneling_sample: %s: The target is not defined. Using direct beam (Z-axis).\n",
      NAME_CURRENT_COMP);

  VarsV.distance=sqrt(VarsV.tx*VarsV.tx+VarsV.ty*VarsV.ty+VarsV.tz*VarsV.tz);

  /* different ways of setting rectangular area */
  VarsV.aw  = VarsV.ah = 0;
  if (focus_xw) {
  VarsV.xw = focus_xw;
  }
  if (focus_yh) {
    VarsV.yh = focus_yh;
  }
  if (focus_aw) {
    VarsV.aw = DEG2RAD*focus_aw;
  }
  if (focus_ah) {
    VarsV.ah = DEG2RAD*focus_ah;
  }

  /* Check that probabilities are positive and do not exceed unity */
  if (f_tun<0)
    ftun=0;
  else
    ftun=f_tun;
  if(f_QE<0)
    fQE=0;
  else
    fQE=f_QE;
  if ((ftun+fQE)>1) {
    ftun=0;
    printf("Tunneling_sample: Sum of inelastic probabilities > 1. Setting f_tun=0");
    if (fQE>1) {
      fQE=0;
      printf("Tunneling_sample: Probability fQE > 1. Setting fQE=0.");
    }
  }
%}

TRACE
%{
  double t0, t3;                /* Entry/exit time for outer cylinder */
  double t1, t2;                /* Entry/exit time for inner cylinder */
  double v;                     /* Neutron velocity */
  double dt0, dt1, dt2, dt;     /* Flight times through sample */
  double l_full;                /* Flight path length for non-scattered neutron */
  double l_i, l_o=0;            /* Flight path lenght in/out for scattered neutron */
  double my_a=0;                /* Velocity-dependent attenuation factor */
  double solid_angle=0;         /* Solid angle of target as seen from scattering point */
  double aim_x=0, aim_y=0, aim_z=1;   /* Position of target relative to scattering point */
  double v_i, v_f, E_i, E_f;    /* initial and final energies and velocities */
  double dE;                    /* Energy transfer */
  double scatt_choice;          /* Representing random choice of scattering type */
  int    intersect=0;

  if (VarsV.isrect)
    intersect = box_intersect(&t0, &t3, x, y, z, vx, vy, vz, xwidth, yheight, zdepth);
  else
    intersect = cylinder_intersect(&t0, &t3, x, y, z, vx, vy, vz, radius, yheight);
  if(intersect)
  {
    if(t0 < 0) ABSORB; /* we already passed the sample; this is illegal */
    /* Neutron enters at t=t0. */
    if(VarsV.isrect)
      t1 = t2 = t3;
    else
      if(!thickness || !cylinder_intersect(&t1, &t2, x, y, z, vx, vy, vz, radius-thickness, yheight))
        t1 = t2 = t3;

    dt0 = t1-t0;                /* Time in sample, ingoing */
    dt1 = t2-t1;                /* Time in hole */
    dt2 = t3-t2;                /* Time in sample, outgoing */
    v = sqrt(vx*vx + vy*vy + vz*vz);
    l_full = v * (dt0 + dt2);   /* Length of full path through sample */
    if (v) my_a = VarsV.my_a_v*(2200/v);

    if (p_interact >= 1 || rand01()<p_interact)          /* Scattering */
    {
      dt = rand01()*(dt0+dt2);    /* Time of scattering (relative to t0) */
      l_i = v*dt;                 /* Penetration in sample: scattering+abs */
      if (dt > dt0)
        dt += dt1;                /* jump to 2nd side of cylinder */

      PROP_DT(dt+t0);             /* Point of scattering */

      if ((VarsV.tx || VarsV.ty || VarsV.tz)) {
        aim_x = VarsV.tx-x;       /* Vector pointing at target (anal./det.) */
        aim_y = VarsV.ty-y;
        aim_z = VarsV.tz-z;
      }
      if(VarsV.aw && VarsV.ah) {
        randvec_target_rect_angular(&vx, &vy, &vz, &solid_angle,
          aim_x, aim_y, aim_z, VarsV.aw, VarsV.ah, ROT_A_CURRENT_COMP);
      } else if(VarsV.xw && VarsV.yh) {
        randvec_target_rect(&vx, &vy, &vz, &solid_angle,
          aim_x, aim_y, aim_z, VarsV.xw, VarsV.yh, ROT_A_CURRENT_COMP);
      } else {
        randvec_target_circle(&vx, &vy, &vz, &solid_angle, aim_x, aim_y, aim_z, focus_r);
      }
      NORM(vx, vy, vz);

      scatt_choice = rand01();  /* chooses type of scattering */
      v_i = v;                  /* Store initial velocity in case of inel. */
      E_i = VS2E*v_i*v_i;
      if (scatt_choice<(fQE+ftun))    /* Inelastic choices */
	{
          if (scatt_choice<fQE) /* Quasielastic */
          { dE = gamma*tan(PI/2*randpm1());
	  }
	  else
          { if (randpm1()>0)
	      dE = E_tun;
		else
              dE = -E_tun;
	  }
          E_f = E_i + dE;
          if (E_f <= 0)
            ABSORB;
	  v_f = SE2V*sqrt(E_f);
          v = v_f;
	}

      vx *= v;
      vy *= v;
      vz *= v;

      if(!VarsV.isrect) {
        if(!cylinder_intersect(&t0, &t3, x, y, z, vx, vy, vz, radius, yheight))
        {
          /* ??? did not hit cylinder */
          printf("FATAL ERROR: Did not hit cylinder from inside.\n");
          exit(1);
        }
        dt = t3; /* outgoing point */
        if(thickness && cylinder_intersect(&t1, &t2, x, y, z, vx, vy, vz, radius-thickness, yheight) &&
           t2 > 0)
          dt -= (t2-t1);            /* Subtract hollow part */
      }
      else
      {
      if(!box_intersect(&t0, &t3, x, y, z, vx, vy, vz, xwidth, yheight, zdepth))
        {
          /* ??? did not hit box */
          printf("FATAL ERROR: Did not hit box from inside.\n");
          exit(1);
        }
        dt = t3;
      }
      l_o = v*dt; /* trajectory after scattering point: absorption only */

      p *= v/v_i*l_full*VarsV.my_s*exp(-my_a*(l_i+v_i/v*l_o)-VarsV.my_s*l_i);
      /* We do not consider scattering from 2nd part (outgoing) */
      p /= 4*PI/solid_angle;
      p /= p_interact;

      /* Polarisation part (1/3 NSF, 2/3 SF) */
      sx *= -1.0/3.0;
      sy *= -1.0/3.0;
      sz *= -1.0/3.0;

      SCATTER;
    }
  else /* Transmitting; always elastic */
    {
      p *= exp(-(my_a+VarsV.my_s)*l_full);
      p /= (1-p_interact);
    }
  }
%}

MCDISPLAY
%{

  if (!VarsV.isrect)
  {
    circle("xz", 0,  yheight/2.0, 0, radius);
    circle("xz", 0, -yheight/2.0, 0, radius);
    line(-radius, -yheight/2.0, 0, -radius, +yheight/2.0, 0);
    line(+radius, -yheight/2.0, 0, +radius, +yheight/2.0, 0);
    line(0, -yheight/2.0, -radius, 0, +yheight/2.0, -radius);
    line(0, -yheight/2.0, +radius, 0, +yheight/2.0, +radius);
    if (thickness)
    {
      double radius_i=radius-thickness;
      circle("xz", 0,  yheight/2.0, 0, radius_i);
      circle("xz", 0, -yheight/2.0, 0, radius_i);
      line(-radius_i, -yheight/2.0, 0, -radius_i, +yheight/2.0, 0);
      line(+radius_i, -yheight/2.0, 0, +radius_i, +yheight/2.0, 0);
      line(0, -yheight/2.0, -radius_i, 0, +yheight/2.0, -radius_i);
      line(0, -yheight/2.0, +radius_i, 0, +yheight/2.0, +radius_i);
    }
  }
  else
  {
    double xmin = -0.5*xwidth;
    double xmax =  0.5*xwidth;
    double ymin = -0.5*yheight;
    double ymax =  0.5*yheight;
    double zmin = -0.5*zdepth;
    double zmax =  0.5*zdepth;
    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
