Kurennoy, S.S.

Paper	Title	Page
WEOBCH02	Design, Construction, and Initial Operation of the SNS MEBT Chopper System	150
	R.A. Hardekopf, S.S. Kurennoy, J. Power LANL, Los Alamos, New Mexico A.V. Aleksandrov, D.E. Anderson ORNL/SNS, Oak Ridge, Tennessee
	The chopper system for the Spallation Neutron Source (SNS) provides a gap in the beam for clean extraction from the accumulator ring. It consists of a pre-chopper in the low-energy beam transport (LEBT) and a faster chopper in the medium-energy beam transport (MEBT). We report here on the final design, fabrication, installation, and first beam tests of the MEBT chopper. The traveling-wave deflector is a meander-line design that matches the propagation of the deflecting pulse with the velocity of the beam at 2.5 MeV, after the radio-frequency quadrupole (RFQ) acceleration stage. The pulser uses a series of fast-risetime MOSFET transistors to generate the deflecting pulses of ± 2.5 kV with rise and fall times of 10 ns. We describe the design and fabrication of the meander line and pulsers and report on the first operation during initial beam tests at SNS.
	Video of talk
	Transparencies
TUPLT008	A Retrofit Technique for Kicker Beam-coupling Impedance Reduction	1144
	F. Caspers, E.H.R. Gaxiola, T. Kroyer, M. Timmins, J.A. Uythoven CERN, Geneva S.S. Kurennoy LANL/LANSCE, Los Alamos, New Mexico
	The reduction of the impedance of operational ferrite kicker structures may be desirable in order to avoid rebuilding such a device. Often resistively coated ceramic plates or tubes are installed for this purpose but at the expense of available aperture. Ceramic U-shaped profiles with a resistive coating fitting between the ellipse of the beam and the rectangular kicker aperture have been used to significantly reduce the impedance of the magnet, while having a limited effect on the available physical aperture Details of this method, constraints, measurements and simulation results as well as practical aspects are presented and discussed.