1 package org.lcsim.recon.tracking.magfield;
2
3 import org.lcsim.recon.tracking.spacegeom.SpacePoint;
4 import org.lcsim.recon.tracking.spacegeom.SpacePointTensor;
5 import org.lcsim.recon.tracking.spacegeom.SpacePointVector;
6
7 /**
8 * AbstractMagneticField is a general magnetic field class which returns values
9 * interesting for tracking code. A magnetic field will generally have an
10 * internal representation optimized for speed which will need to be updated
11 * whenever the field is moved or rescaled. Important methods are:
12 *
13 *
14 * SpacePointVector field( SpacePoint p); SpacePointVector field( SpacePoint p,
15 * SpacePointTensor g); return the field at p and calculates the gradient
16 * tensor. The returned field and the gradient are in the form of a value at the
17 * point p.
18 *
19 *
20 * Note regarding gradient tensor:
21 *
22 * The gradient tensor is a matrix of covariant derivates, which can be defined,
23 * or its components extracted, in any standard coordinate system (namely,
24 * Cartesian, cylindrical, spherical).
25 *
26 * In Cartesian coordinates, covariant derivatives is the same as ordinary
27 * partial derivatives:
28 *
29 * Bi;j = Bi,j (i,j = x,y,z)
30 *
31 * In Cylindrical coordinates, the physical components of the covariant gradient
32 * tensor are as follows:
33 *
34 * Br;r = Br,r
35 * Br;phi = (1/r)Br,phi - Bphi/r
36 * Br:z = Br,z
37 * Bphi;r = Bphi,r
38 * Bphi;phi = (1/r)Bphi,phi + Br/r
39 * Bphi;z = Bphi,z
40 * Bz;r = Bz,r
41 * Bz;phi = (1/r)Bz,phi
42 * Bz;z = Bz,phi
43 *
44 *
45 *
46 *
47 * @author Norman A Graf
48 *
49 * @version $Id:
50 */
51 public abstract class AbstractMagneticField
52 {
53 // given a space position, return a field object
54
55 public abstract SpacePointVector field(SpacePoint p);
56 // given a space position, return a field object and calculate
57 // the covariant gradient.
58
59 public abstract SpacePointVector field(SpacePoint p, SpacePointTensor g);
60 }