Jefferson Lab's electron beam is an exciting tool for physics research; however, if the hair's-width beam doesn't stay focused, centered during its travels or hit the target precisely, it is nothing more than wasted energy.

Electric magnets are vital for these jobs. "If just one magnet isn't functioning properly, we have steering and focusing problems," explains Simon Wood, senior electronics technologist in Accelerator Electronics Support (AES), who maintains the accelerator's magnet system. And the most vital part of the magnet system is its power supply.

Simon Wood calibrates the voltage and current output and frequency on one of the bulk power supply units.

The magnets' bulk DC power supply components are installed in several locations around the accelerator - housed in blue and gray boxes nestled together on banks of equipment racks. To the uninitiated, their most noticeable quality is the low-pitched hum they emit when their fans kick in. Their plain appearance belies their importance to accelerator operations.

A constant power supply is vital to running all 2,200 of the Continuous Electron Beam Accelerator's magnets, according to Wood. The electricity from Virginia Power fluctuates between 190 and 230 volts AC (alternating current); this power is transformed to DC (direct current) power and the output voltage is maintained at a constant 30 volts DC so it can be used to power the magnets. "The output voltage [from the power supplies] must be well regulated to provide constant current to the magnets," he points out. "If the output level drops by as little as .4 of a volt, it causes problems for the accelerator. The quadrupole magnets are very sensitive to power fluctuations."

"Last year the magnets weren't keeping the beam focused as precisely as needed in the accelerator. We were having problems with beam reproducibility, which is a high-interest item for the physicists," Wood explained. "Reproducibility is being able to turn the accelerator off and back on and put the beam in exactly the same place it was before we turned the machine off."

"We noticed that the beam was drifting - in a cyclical nature. We were having an awkward time putting the beam back into its original location and keeping it there."

The nature of the problem led Simon to the bulk power supplies. He analyzed the power supply components and identified the causes for the Lab's magnet problems. He discovered a secondary power supply circuit causing problems within the units; and a relaxation oscillator circuit inside the power supply units that provides output directly proportional to the AC power input entering the component - resulting in just enough power variance to disrupt the energy fields produced by the magnets.

Wood redesigned the relaxation oscillator to make sure the bulk power supply would provide a constant 30-volt DC output despite the AC power input variance of up to 40 volts. He also suggested modifications to the power supply to handle the magnets' needs during high-energy runs. He proposed replacing some internal components in each bulk power supply unit and calibrating components within each unit, increasing the power supply's potential output to 35 volts.

These changes approved, Simon set to work. All told, Wood and his team modified some 150 power supply units. The process included disassembly, cleaning, drying, modifying, rebuilding, and testing each unit. In an unconventional twist for electronic components, cleaning included hosing the power supply units down with water and using a household all-purpose cleaner on them. Wood and five contract employees handled most of the workload; however, they were assisted by a number of AES technicians during specific steps in the process - all completed during the June 1999 maintenance month. Wood is happy with the results. "The modifications turned out great. We don't see beam drift like we did before," he said. "Of all the projects I've worked on in my eight years here, this was the most challenging and demanding. I'm very pleased with the outcome."

SURA has applied for a patent for Wood's voltage regulator and bulk power supply design. Manufacturer EMI (Electronic Measurement, Inc.) now uses Wood's circuit modification in its new power supplies.

As if Wood's work doesn't keep him busy enough, he and his wife, Earnestine, have two adult children and have been foster parents for 19 additional children over the last seven years. Many of the youth, ranging in age from 12 to 17, have been beset with problems. Wood and his wife provide them with encouragement, religion and a safe home with rules and guidance. "Coming into our home is an adjustment for many of them. Most of them have never had a father around - just a mother trying to do both jobs - so they've never had to answer to a man," Wood said. "One of our foster children is in his second year in the Marines. He followed me around a lot at home - watching me work on TVs and VCRs. Now he's an electronics communication specialist; I'm very proud of him."

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