RITA - relativistic transparency of an UPHILL over-dense target for a compact proton and ions source of controllable energy

The Relativistically Induced Transparency Acceleration (RITA) scheme of proton and ion acceleration using laser-plasma interactions is introduced, modeled and compared to existing schemes.
Protons are accelerated with femtosecond relativistic pulses to produce bunches that are mono-energetic and have a controllable peak energy.
The RITA scheme works by creating a traveling acceleration structure, a snowplow of electrons, driven directly by the laser at the critical plasma density. The snowplow advances with a velocity determined by the rate of the rise of laser's intensity at the head of the pulse and the plasma density gradient scale length. The transparency is increased in a controlled way to ensure that the relativistic plasma electron frequency is resonant with the laser field. In the snowplow frame, protons reflect off the snowplow's electrostatic potential while the heavier background ions are relatively unperturbed. Mono-energetic bunches of velocity equal to twice the snowplow velocity can be obtained and tuned by controlling the snowplow velocity. An analytical model for the proton energy as a function of laser intensity, rise-time and plasma density-gradient is developed and compared to 1-D and 2-D PIC simulations.
GeV proton bunches can be obtained with laser pulses of length 25fs and peak power 2.5PW. The scaling of proton energy with laser power compares favorably to other mechanisms for ultra-short pulses.