Ripple Cancellation Supply

Synchrotron light sources, such as the Advanced Photon Source (APS) at Argonne National Laboratory, produce X-rays that are focused on users’ targets. The position of these X-rays, however, is not fixed but moves. The motion of the X-rays is caused by motion of the electron beam within the accelerator, this, in turn, is caused by variation in the accelerating RF. The RF variation is largely due to the power supplies that drive the RF tubes. These supplies, which operate at 60 Hz, have large power transformer-rectifiers controlled by SCRs on the primary side that phase back the output voltage. The output ripple of these supplies is significant – about 1 kV, 1% of the output voltage – at 360 Hz and other 60 Hz harmonics. APS already uses low-level RF feedback to reduce the RF variation, which is as low as it can be with the present hardware. To further reduce the RF variation we will add a small switching power supply in series with the main supply. The additional supply will produce an AC voltage opposite to the ripple voltage of the SCR supply, cancelling the ripple on the RF tubes. This ripple-cancellation supply will reduce the DC voltage variation at APS by more than two orders of magnitude to less than 10 V peak-to-peaks. Commercial Applications and Other Benefits: This technology has the ability to impact a number of high voltage system designs currently based on SCR power supplies, especially in industrial applications. Many of these systems, whether used to produce RF, operate into plasma, or in industrial applications such as semiconductor fabrication or crystal growth, would experience similar improvements in performance if their voltage control was improved.