/** University College London Dept of Physics Course in OO 3C59 
| all rights reserved 2000
|
| Utility: The Rod class
|
|   This class simulates the combination of the radioactive sourse and the
|   scattering rod.
|
|   Its main function is to provide Photons on demand with an angular
|   distribution corresponding to that of the real scattered photons
|   in the experiment
|
| Author: P.Clarke 
*/

//package uk.ac.ucl.hep.ComptonMC ;

import java.lang.Math ;

public class Rod {

  private double m_sourceEnergy ;  // energy of photons from the radioactive source
  private double m_electronMass ;  // Electron mass in kev

  private RanCom m_angleGenerator; // Helper to generate random angle


  //-------------
  // Constructor.
  public Rod( double sourceEnergy, double electronMass ) 
  {
    m_sourceEnergy = sourceEnergy ;
    m_electronMass = electronMass ;
	m_angleGenerator = new RanCom( m_sourceEnergy, m_electronMass ) ;
  }


 
  //-------------
  // Private methods to help out
  // This one calculates the energy corresponding to the scattering angle
  private double calculateEnergy( double angle ) 
  {
    double angleInRadians = angle * Math.PI / 180.0 ;

		 double invE = (1.0/m_sourceEnergy) + 
                  (1.0/m_electronMass) - 
                  ( Math.cos( angleInRadians ) / m_electronMass ) ;

		 return 1.0/invE ;
  }


  // -------------------------
  // Main method to return a new photon to the client with an angle and energy
  // corresponding to the true compton scattering distribution
  public Photon generatePhoton() 
  {
      // Generate a new random angle
    double angle = m_angleGenerator.scatter( ) ;

    // Calculate the corresponding energy
    double energy = this.calculateEnergy( angle ) ;

    // Create and return a photon
    Photon p = new Photon( energy, angle ) ;

    return p ;
  }



}