Misc,
Long Term Evolution of Plasma Wakefields
(May 16, 2014)
Abstract
We study the long-term evolution (LTE) of plasma wakefields over multiple
plasma-electron periods and few plasma-ion periods, much less than a
recombination time. The evolution and relaxation of such a wakefield-perturbed
plasma over these timescales has important implications for the upper limits of
repetition-rates in plasma colliders. Intense fields in relativistic lasers (or
intense beams) create plasma wakefields (modes around ømegape) by
transferring energy to the plasma electrons. Charged-particle beams in the
right phase may be accelerated with acceleration/focusing gradients of tens of
GeV/m. However, wakefields leave behind a plasma not in equilibrium, with a
relaxation time of multiple plasma-electron periods. Ion motion over ion
timescales, caused by energy transfer from the driven plasma-electrons to the
plasma-ions can create interesting plasma states. Eventually during LTE, the
dynamics of plasma de-coheres (multiple modes through instability driven
mixing), thermalizing into random motion (second law of thermodynamics),
dissipating energy away from the wakefields. Wakefield-drivers interacting with
such a relativistically hot-plasma lead to plasma wakefields that differ from
the wakefields in a cold-plasma.
