Measurements on Combined 12.5/17.5 Kv Prototype Inductive Adder for the Clic Dr Kickers

The CLIC study is investigating the technical feasibility of an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The pre-damping rings (PDR) and damping rings (DRs) will produce ultra-low emittance beam with high bunch charge. To avoid beam emittance increase, the DR kicker systems must provide extremely stable field pulses during injection and extraction of bunches. Each DR extraction kicker system consists of a stripline kicker and two pulse modulators. The present specification for the DR extraction modulators calls for pulses with 160 ns or 900 ns flattop duration of nominally +/-12.5 kV and 305 A, with ripple of not more than +/-0.02 % (+/-2.5 V). In addition, there is a proposal to use the same modulators and striplines for dumping the beam, with +/-17.5 kV stripline pulse voltage. An inductive adder is a very promising approach to meeting the CLIC DR extraction kicker specifications because analogue modulation methods can be applied to adjust the shape of the flattop of the output waveform. Two full-scale, 12.5 kV, 20-layer, prototype inductive adders have been designed, built and tested at CERN. These two adders have also been tested in series connection to facilitate two operation modes: 12.5 kV pulses for extraction kicker operation and 17.5 kV for dump kicker operation. The results of laboratory tests of full-scale prototypes are presented.