&set_constant_fields
Ez = 1e3,
Bz = 1,
&end
This command specifies a constant longitudinal electric field
of 1 kV/m and a constant longitudinal magnetic field of 1 T.
Note that these are physically possible, at least in the absence
of metallic or magnetic materials.
&constant_fields
double Ez = 0;
double Er = 0;
double Ephi = 0;
double Bz = 0;
double Br = 0;
double Bphi = 0;
&end