Wittig, G., Karger, O., Knetsch, A., Xi, Y., Deng, A., Rosenzweig, J.B., Bruhwiler, D.L., Smith, J., Manahan, G.G., Sheng, Z.M. and Jaroszynski, D.A., 2015. Optical plasma torch electron bunch generation in plasma wakefield accelerators. Physical Review Special Topics-Accelerators and Beams, 18(8), p.081304.