Parametric study of high-energy ring-shaped electron beams from a laser wakefield accelerator oleh A Maitrallain, E Brunetti, M J V Streeter, B Kettle, R Spesyvtsev, G Vieux, M Shahzad, B Ersfeld, S R Yoffe, A Kornaszewski, O Finlay, Y Ma, F Albert, N Bourgeois, S J D Dann, N Lemos, S Cipiccia, J M Cole, I G González, L Willingale, A Higginbotham, A E Hussein, M Šmid, K Falk, K Krushelnick, N C Lopes, E Gerstmayr, C Lumsdon, O Lundh, S P D Mangles, Z Najmudin, P P Rajeev, D R Symes, A G R Thomas, D A Jaroszynski