Rectangular box with constant B field along y-axis (up). The
component can be rotated to make either a guide field or a spin
flipper. A neutron hitting outside the box opening or the box sides
Example: Pol_constBfield(xwidth=0.1, yheight=0.1, length=0.2, fliplambda=5.0)
Parameters in boldface are required;
the others are optional.
Width of opening (m).
Height of opening (m).
Length of field (m).
Magnetic field along y-direction
lambda for calculating B field
Angle flipped for lambda = fliplambda
fliplambda and flipangle overrides B so a neutron with s
= (1, 0, 0) and v = (0, 0, v(fliplambda)) will have s =
(cos(flipangle), sin(flipangle), 0) after the section.