I have archived three versions of the Nab detector
GEANT4 simulations - G4.6.2.p01 (no spin), G4.6.2.p01 
(tracking with spin) and the latest (Dec. 2005) G4.8.0.
They use CLHEP-1.8.0.0 and CLHEP-1.9.2.2, respectively.

The code is based on the G4 distribution example
geant4.*/examples/extended/electromagnetic/TestEm5/

The electromagnetic fields are defined using the
the Fermilab BeamTools BT-v1.50.tar.gz, in particular
the MuCool.cc example, as a template.  

The simulations use the full 3D electromagnetic
field read in from the text file with 1mm^3 grid,
and interpolate in 3D to find magnetic and
electric fields at the point. The sensitive detectors
are two 2mm thick Silicon disks with 16.2mm diameter.
Basic passive spectrometer elements are also defined 
in the geometry.

The input particles can be electrons, protons or
decaying neutrons. We have defined the special
type of theneutron "abBANeutron". The input parameters 
and output variables are read/saved in the text files 
for now.

Nab source code, GEANT.4.6.2.p01 version,
is the MC of the Nab spectrometer.

Nab source code, GEANT.4.6.2.p02 version,
has modification in G4Transportaion.cc 
that enables tracking of neutral particles
with spin, e.g. neutrons.
The equations of motions are specified in
src/G4Mag_Neutron_SpinEqRhs.cc

Nab with spin source code, GEANT4.6.2.p02 version,
is the MC of the Nab spectrometer with spin tracking.

Nab source code, GEANT4.8.0 version,
is again the MC of the Nab spectrometer.

			    Emil Frlez, Apr. 28, 2006