Measurement and Characterization of Cable Losses for High Voltage Coaxial Cables Used in Kicker Systems

In the framework of CERN's LHC Injector Upgrade, simulation models for kicker pulse generators have been improved. A key element in the conventional pulse generators, among many others, are the high voltage coaxial cables. Since they can have significant impact on the waveform characteristics, an accurate cable model for simulation is crucial for reliable results during development. For this purpose, precise measurements of scatter parameters have been carried out in order to improve existing simulation models. Specialized high voltage cables, sometimes SF6 gas filled, used in various CERN kicker systems are usually large, heavy, not very flexible and often only one end is easy accessible. In addition, the impedance of these cables is rarely of 50 Ohms, which presents an extra difficulty. This paper describes the methods that have been defined and used to measure any kind of coaxial structures relying on S11 parameters exclusively. Measurements for various specialized cable types are presented and compared with their improved models. The implications for overall kicker system performance are briefly discussed.