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4 SECTIONS FORMAT
96
4.15.2 Neutron
The definition of the magnetic field for neutron is almost the same as for charged particles. Here we describe
the detail of the magnetic field for neutron.
[ Magnetic Field ]
reg
typ
gap
1
60
0.00000
2
61
0.00000
3
106
5.00000
4
104
0.00000
5
102
0.00000
6
101
3.00000
7
103
0.00000
...
...
........
...
...
........
mgf
35000.0
35000.0
7130.0
3.5
0.20
7130.0
35000.0
........
........
trcl
3
1
0
0
0
2
0
...
...
polar
non
1
0
non
non
1
-1
...
...
time
non
non
non
5.0
non
non
non
...
...
We can not take into account of the gravity nor additional dipole magnet. For 60 case, it is assumed that the
spin always keeps parallel or anti-parallel to the magnet field. For 61 case, we solve the coupled equation of motion
between the spin and the magnetic field. Then the spin flip can be occurred in the region with weak magnetic field.
The strength of the magnetic field is specified in the unit of [T/m2 ] in mgf column.
For the types above 100, we consider the coupled equations of the spin and the magnetic field. In addition, the
effects of the gravity and additional dipole field can be taken into account. 106 is sextupole, 104 quadrupole, and
102 dipole, respectively. The strength of additional quadrupole magnet (z-direction) is give by the column of gap
in the unit of [T].
For 101 type, the magnetic field is defined by the user program file, usrmgf1.f. In this user program, the data
measured by the neutron optics group in JAERI are read from the file and used the calculation. The strength of this
field is renormalized by the value of mgf.
For 101 type, the magnetic field is also defined by the user program file, usrmgf3.f. In this user program, there
is a simple sextupole magnet field as same as in 106 type.
The neutron goes into the magnetic field with the initial spin if it is defined in the source section. If not, the
initial spin is defined at the moment when the neutron goes into the magnetic field. The ratio of the number of
parallel and anti-parallel spin to the magnetic field is determined by the polarization defined by the polar column.
non in polar column means 0 polarization. The polarization is defined as
P=
ϕ+ − ϕ−
,
ϕ+ + ϕ−
here, ϕ+ and ϕ− are the number of the parallel and anti-parallel particles.