package org.lcsim.geometry.field;
   
   import hep.physics.vec.BasicHep3Vector;
   import org.jdom.Element;
   import org.jdom.JDOMException;
   
   /**
    * Solenoidal magnetic field.
    * @author tonyj
   */
  
  public class Solenoid extends AbstractFieldMap
  {
     private double[] innerField;
     private double[] outerField;
     private double zmax;
     private double outerRadiusSquared;
  
     Solenoid(Element node) throws JDOMException
     {
        super(node);  
  
        double i  = node.getAttribute("inner_field").getDoubleValue();
        innerField = new double[] { 0, 0, i};
        double o = node.getAttribute("outer_field").getDoubleValue();
        outerField = new double[] { 0, 0, o};
        zmax = node.getAttribute("zmax").getDoubleValue();
        double r = node.getAttribute("outer_radius").getDoubleValue();
        outerRadiusSquared = r*r;
     }
  
     void getField(double x, double y, double z, BasicHep3Vector field)
     {
        if (Math.abs(z)>zmax) field.setV(0,0,0);
        else
        {
           double r2 = x*x + y*y;
           double bz = (r2 > outerRadiusSquared) ? outerField[2] : innerField[2];
           field.setV(0,0,bz);
        }
     }
  
     public double[] getInnerField()
     {
         return innerField;
     }
  
     public double[] getOuterField()
     {
         return outerField;
     }
  
     public double getZMax()
     {
         return zmax;
     }
  
     public double getOuterRadius2()
     {
         return outerRadiusSquared;
     }
  }