Instability of a witness bunch in a plasma bubble
  The stability of a trailing witness bunch, accelerated by a plasma wake accelerator (PWA) in a blow-out regime, is discussed. The instability growth rate as well as the energy spread, required for BNS damping, are obtained. A relationship between the PWA power efficiency and the BNS energy spread is derived. 
A. Burov, V. Lebedev and S. Nagaitsev
physics.acc-ph