We demonstrate that a relativistic electron beam is properly described in t
he moving frame by the electron-magnetohydrodynamic equations of plasma phy
sics. For large beam currents, the accelerator magnetic held is expected to
be unstable to the fast magnetic reconnection. We present a plausible satu
rated state of the fast reconnection, in the form of a complex vortex patte
rn. The nonlinear dispersion equations of the vortex are derived and the re
lationship between the vortex structure and the background magnetic field i
s discussed.