The Forward GEM Tracker consists of 6 disks, each composed of four quadrants. Each of the six disks is fixed at point (x',y',z') which may be offset from the nominal position at STAR (x,y,z). Tables xoff,yoff and zoff account for this offset.

Each of these 24 subsections (6 disks x 4 quads) has three degrees (phi, theta, psi) of freedom with respect to their nominal locations within the STAR framework. The nominal locations can be determined using the StFgtGeom class. Phi, theta and psi are the proper Euler Angles as defined by Eric Weisstein in Mathworld : http://mathworld.wolfram.com/EulerAngles.html.

These values should be uploaded each time the FGT is removed and then reinserted back to STAR.

**** fgtAlignment.idl ****

/* Allows for fixed rotation of each quadrant WRT STAR xyz
Index for phi, theta, phi = 4*n_disks + n_quads
Index for xoff, yoff, off = n_ndisks
n_disks runs from 0 - 5
n_quads runs form 0 - 3
*/

struct fgtAlignment
{
double phi[24];
double theta[24];
double psi[24];
double xoff[24];
double yoff[24];
double zoff[24];

}