The advanced photon source linac modulators PSpice simulation and upgrade

Abstract

The main elements are 30 kJ/s EMI power supply, 2×8-cell PFN, EEV thyratron switch, and 15.2:1 step-up pulse transformer (PT). In operation, the charging supply charges the PFN capacitors to up to 40 kV and then the thyratron switch discharges the PFN into the matched 4-Ω reflected load of the klystron cathode. The process then repeats at a 30 p.p.s. rate. The modulator has a fairly standard design and has been presented at various particle accelerator conferences [1,2].The APS linac modulators provide DC pulses to Thales 35/45-MW klystrons. The modulators are pulse forming network (PFN)-type pulsers with EMI 40-kV switch-mode charging supplies. The PFN consists of two 8-cell lines connected in parallel. EEV CX1836A thyratrons are used as discharge switches.The PSpice simulation of the modulators using OrCAD release 9.1 made it possible to find appropriate parameters of RC circuits that reduce high-frequency ringing of the pulse transformer primary voltage.