Soller_trans.comp

[Dr. Georg Artus]

Hello Kristian,

I just modified the component Soller to Soller_trans. The new component
has an additional parameter transmission, which is a general
multiplicator for the transmission probability. The true transmission of
a Soller is not 1 also with a non divergent beam. For calculations of
absolute fluxes this is important.
Because I am not experience with C (I just checked Soller.comp by
mathematical undterstanding) I don´t want to send the new component to
the mailing-list directly. I also didn´t add a check whether the given
parameter ´transmission´ lies between 0 and 1. 
Our tests indicate that the component works correctly. May be you can
have a look at the file.

Georg 
-- 
*********************************************

Dr. Georg Artus
Technische Universitaet Muenchen
Neue Forschungs-Neutronenquelle Garching
D-85747 Garching

Tel: +49 (0)89/289-14675
Fax: +49 (0)89/289-14666 or 12112
E-mail: gartus at ph.tum.de

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/*******************************************************************************
*
* McStas, version 1.0, released October 26, 1998
*         Maintained by Kristian Nielsen and Kim Lefmann,
*         Risoe National Laboratory, Roskilde, Denmark
*
* Component: Soller_trans
*
* Written by: KN, August 1998
* Modified by: GA, June 1999
*
* Soller collimator with rectangular opening and specified length. The
* transmission function is an average and does not utilize knowledge of the
* actual neutron trajectory.
* A zero divergence disables collimation (then the component works as a double slit).
* Added is an additional parameter ´transmission´ to take into account the
* transmission probability. 
*
* INPUT PARAMETERS:
*
* xmin:       (m)              Lower x bound on slits
* xmax:       (m)              Upper x bound on slits
* ymin:       (m)              Lower y bound on slits
* ymax:       (m)              Upper y bound on slits
* len:        (m)              Distance between slits
* divergence: (minutes of arc) Divergence angle (calculated as atan(d/len),
*                              where d is the blade spacing) 
* transmission: (1)            0<=transmission<=1)
*
*******************************************************************************/


DEFINE COMPONENT Soller_trans
DEFINITION PARAMETERS (xmin, xmax, ymin, ymax, len, divergence, transmission)
SETTING PARAMETERS ()
OUTPUT PARAMETERS (slope)
STATE PARAMETERS (x,y,z,vx,vy,vz,t,s1,s2,p)
DECLARE
%{
  double slope;
%}
INITIALIZE
%{
  slope = tan(MIN2RAD*divergence);
%}
TRACE
%{
    double phi, dt;
    
    PROP_Z0;
    if (x<xmin || x>xmax || y<ymin || y>ymax)
      ABSORB;
    dt = len/vz;
    PROP_DT(dt);
    if (x<xmin || x>xmax || y<ymin || y>ymax)
      ABSORB;

    if(slope > 0.0)
    {
      phi = fabs(vx/vz);  
      if (phi > slope)   
        ABSORB;
      else
        p *= transmission*(1.0 - phi/slope);
    }
%}

MCDISPLAY
%{
  double x;
  int i;

  magnify("xy");
  for(x = xmin, i = 0; i <= 3; i++, x += (xmax - xmin)/3.0)
    multiline(5, x, (double)ymin, 0.0, x, (double)ymax, 0.0,
              x, (double)ymax, (double)len, x, (double)ymin, (double)len,
              x, (double)ymin, 0.0);
  line(xmin, ymin, 0,   xmax, ymin, 0);
  line(xmin, ymax, 0,   xmax, ymax, 0);
  line(xmin, ymin, len, xmax, ymin, len);
  line(xmin, ymax, len, xmax, ymax, len);
%}

END