Fermilab Main Accelerator Quadrupole Transistorized Regulators for Improved Tune Stability

During early operation of the Fermilab Main Accelerator, tune flucutations, caused by the SCR-controlled power supplies in the quad bus, limited the beam aperature at low energies. To correct this problem, two transistorized power supplies were built in 1975 to regulate and filter the Main Ring quad magnet current during injection and beam acceleration through the rf transistion region. There is one power supply in series with each quad bus. Each supply uses 320 parallel power transistors and is rated at 300A, 120V. Since the voltage and current capabilities of the transistorized supplies are limited, the supplies are turned-off at about 25GeV. A real-time computer system initiates turn-on of the SCR-controlled power supplies and regulation takeover by the SCR-controlled supplies, at the appropriate times.