1. Institute for Accelerator Science and Electromagnetic Fields, Technische Universitt Darmstadt, 26536 Darmstadt, Germany, 64289 (e-mail: spaeck@temf.tu-darmstadt.de)
2. Institute for Accelerator Science and Electromagnetic Fields, Technische Universitt Darmstadt, 26536 Darmstadt, Germany, (e-mail: maregreta.ruppert@stud.tu-darmstadt.de)
3. Institute for Accelerator Science and Electromagnetic Fields, Technische Universitt Darmstadt, Darmstadt, Germany, (e-mail: gjonaj@temf.tu-darmstadt.de)
4. Institute for Accelerator Science and Electromagnetic Fields, Technische Universitt Darmstadt, Darmstadt, Germany, (e-mail: degersem@temf.tu-darmstadt.de)
5. High Voltage Laboratories, Darmstadt University of Technology, Darmstadt, Germany, 64283 (e-mail: hinrichsen@hst.tu-darmstadt.de)