Design and initial measurements of a 12.5 kV prototype inductive adder for CLIC DR kickers

The CLIC study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC pre-damping rings and damping rings will produce, through synchrotron radiation, ultra-low emittance beam with high bunch charge, necessary for the luminosity performance of the collider. To limit the beam emittance blow-up due to oscillations, the pulse generators for the damping ring kickers must provide extremely flat, high-voltage pulses. The specifications for the damping ring extraction kickers call for 160 ns or 900 ns duration flat-top pulses of +/- 12.5 kV, 250 A, with a combined ripple and droop of not more than ±0.02 % (±2.5 V). An inductive adder is a very promising approach to meeting the specifications. The first 20-layer prototype inductive adder is being assembled at CERN and initial measurements, with the 5 first layers, have commenced. This paper presents the detailed design of the full-scale, 12.5 kV, 250 A, prototype inductive adder. The prototype adder has an active analogue modulation layer to compensate droop and ripple, in order to reach ultra-low flat-top stability. In this paper, the design of the full-scale 12.5 kV prototype inductive adder is explained in detail and the results of the initial measurements, carried out with the first five assembled layers, are presented.