The UCLA/NICADD plasma density transition trapping experiment

Plasma density transition trapping is a recently purposed self-injection scheme for plasma wake-field accelerators. This technique uses a sharp downward plasma density transition to trap and accelerate background plasma electrons in a plasma wake-field. Two and three dimensional Particle-In-Cell (PIC) simulations show that electron beams of substantial charge can be captured using this technique, and that the beam parameters such as emittance, energy spread, and brightness can be optimized by manipulating the plasma density profile. These simulations also predict that transition trapping can produce beams with brightness > 5 × 10¹⁴ Amp/(m-rad)² when scaled to high plasma density regimes. A proof-of-principle plasma density transition trapping experiment is planned for the near future. This experiment is a collaboration between UCLA and Northern Illinois University (MCADD). The goal of the experiment is to capture a ∼ 100 pC, 1.2 MeV beam with ∼ 4% rms energy spread out of a 2 × 10¹3 cm^-3 peak density plasma using a ∼ 6 nC, 14 MeV drive beam. Status and progress on the experiment are reported.