Efficiency and beam quality for positron acceleration in loaded plasma wakefields

Accelerating particles to high energies in plasma wakefields is considered be a promising technique with good energy efficiency and gradient. While important progress has been made plasma-based electron acceleration, positron acceleration scarcely studied fully self-consistent optimal scenario not yet identified. For physics applications where an electron-positron collider would desired, the ability accelerate positrons is, however, paramount. Here we show that preservation of beam quality can compromised wakefield loaded beam, tradeoff between needs found. beams driving linear wakefields, have found despite transversely nonlinear focusing force induced by loading, bunch quickly evolves toward equilibrium distribution limited emittance growth. Particle-in-cell simulations for $\ensuremath{\mu}\mathrm{m}$-scale normalized emittance, growth uncorrelated spread sets limit. Our results demonstrate or moderately regimes Gaussian drivers provide tradeoff, achieving simultaneously energy-transfer efficiencies exceeding 30% below 1%, while donut-shaped regime are more appropriate high-charge bunches at higher gradients, cost degraded quality.