Evaluation of the cone-shaped pickup performance for low charge sub-10 fs arrival-time measurements at free electron laser facilities oleh Aleksandar Angelovski, Michael Kuntzsch, Marie Kristin Czwalinna, Andreas Penirschke, Matthias Hansli, Cezary Sydlo, Vladimir Arsov, Stephan Hunziker, Holger Schlarb, Michael Gensch, Volker Schlott, Thomas Weiland, Rolf Jakoby