The damping ring kickers for the SLAC Linear Collider must provide 7 mrad kicks to 1.2 GeV beams with 60 nsec rise and fall times and fit in a 50 cm length around a 21 mm diameter ceramic beam pipe. This requires that they operate at up to 40 KV. The construction and operation of two types of quasi-coaxial ferrite magnet potted with RTV silicone rubber is discussed. Production yield has been improved by changes in RTV degassing, transfer, and cure. Operation lifetime is dominated by voltage, radiation. and thermal cycling.
I. DESIGN CONSIDERATIONSThe SLAC Linear Collider (SLC) damping rings are small 1.2 GeV synchrotrons used to reduce the emittance of e+ and ebunches by radiation damping before they are accelerated in the main linac to 50 GeV and collided. The damping ring revolution time is only 120 nsec, and 2 bunches circulate in each ring. so the kicker rise and fall times must be less than 60 nsec. The injection and extraction straight sections'provide no damping so their length was minimized, thus a 7 mrad kick is required to clear the injection and extraction septa. The kickers are located where ring bends were omitted for dispersion suppression. The energy, angle, aperture, and length requirements imply a current of order 2000 A, and the energy, angle, aperture, and time requirements determine a voltage of order 30 KV.The kickers were intended to be terminated transmission lines with the beam in the gap of the ferrite flux return [ 1.21. Ferrite-free current strip kickers would require nearly twice the current of ferrite kickers. Transmission line structures give the optimum pulse response. The magnet pulse is provided by several RG-220 coaxial cables in parallel, and another set of cables carries the pulse to a matched terminating load. The kickers are in the air outside an alumina ceramic beam pipe with a Kovar inner coating (about 1 ohm/square) that prevents the ferrite from being heated by beam image currents, and keeps the ferrite from loading the beam. The ceramic is 50 cm long, 21 mm diameter with 3 mm walls, with a capacitive choke joint at one end to prevent the coating from forming a shorted turn in the magnet, while still allowing beam image *
