Design and development of a 6.25 kV/1 kA PFN to supply the new PS Booster distributor magnets

Abstract

Linac4 is an H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> ion linear accelerator at CERN, intended to replace Linac2 as injector to the PS Booster (PSB). In order to distribute the 160 MeV beam from Linac4 to the four rings of the PSB, new distributor magnets (BI.DIS) and magnetic septa (BI.SMV) need to be built. The proposed distribution scheme requires the construction of five new pulse generators of Pulse Forming Network (PFN) type, to double the magnitude of the BI.DIS field pulse and to increase the maximum duration of the pulse from 140 μs to 620 μs. A prototype PFN featuring 60 cells assembled in a Guillemin type E network was built. A PFN impedance of 6.25 Ω was chosen in order to achieve a magnetic field rise time of 1 μs (1 %-99 %) and a current amplitude of 1 kA in the lumped inductance magnet with a flat top ripple of ± 1%. The nominal operating voltage of 6.25 kV (maximum of 10 kV) and the repetition rate of 1.1 Hz allow operation in air. A switch comprising two commercial IGBTs connected in series will be used to initiate the transfer of the energy from the PFN to the magnet. This document presents the design of the new PFN and the measurements performed with switches from four different suppliers. IGBT rise time improvements, synchronization problems and ideas for timing drift stabilization are discussed. The general layout of the foreseen control system is shown.