High power testing of a prototype clic structure: Td26cc r05 n3

Testing of high gradient accelerating structure prototypes for the Compact Linear Collider is ongoing at CERN. High power testing of the baseline structure CLIC-G, also known as TD26CC R05, from the most recent concept design review was conducted on CERN’s second X- band test stand, Xbox 2. Several months of conditioning resulted in an ultimate unloaded gradient of 110 MV/m, the highest achieved for a structure with higher-order mode damping, with a 170ns flat-top RF pulse and operating with a breakdown rate of 2 ×10−5 breakdowns/pulse/metre. Investigations of the breakdown distribution demonstrated homogenous breakdown behaviour throughout the structure when fields were below 110 MV/m. After high power testing, a measurement of the RF parameters of the structure illustrated a significant change in the S- parameters consequential of a detuning of the cells, equating to a 1 MHz shift in the frequency.