Resonant ramping scheme for CLS booster dipole magnets [Canadian Light Source]

The booster for the proposed Canadian Light Source is being designed to ramp the electron beam from 250 MeV to 2.9 GeV in approximately 180 ms, with a repetition frequency of 2.5 Hz. The booster dipole magnets will be connected in series with a capacitor bank and operated as a series resonant circuit. This approach reduces the peak power drawn from the supply and consequent load fluctuations on the incoming AC lines. The series connection ensures that the current through each magnet is identical. The circuit is simple and easy to control, especially when compared to other ramping power supply approaches. An SCR bank, configured as an H-Bridge, controls the orientation of the capacitor bank in the circuit. To initiate a ramp cycle two opposing legs of the bridge are switched on, thereby applying power to the magnets. The magnet current is a half sinusoid; when it drops to zero the SCRs turn off with the capacitors charged to the opposite polarity, ready for the next cycle. The system will apply a peak voltage of approximately 3500 V and a peak current of 1550 A to the magnet string.