The APS septum magnet power supplies upgrade

The higher requirements for beam injection stability at the APS storage ring (SR) demand improvement of pulsed power supplies for the septum magnets. The new specification for the current repeatibility is 1/2000. The upgrade will be performed in two stages. In the first stage we will implement a new voltage regulation circuit in the power supply with a new timing sequence that will provide better voltage regulation performance. A common design is made for all of the septum magnet power supplies (SMPSs) at the APS. The new regulation module has already been tested on both thin and thick SMPSs. The test shows that the achieved voltage regulation is much better than 1/2000. Combined with a current feedback loop, it can provide a shot-to-shot current repeatability better than 1/2000. The second phase of the upgrade will develop the current feedback loop and control algorithm. This paper will decribe the design and test results for the first phase only.