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David MacNair Keeps the Power On

(Photo - David MacNair)
Dave MacNair with his prototype of a next-generation redundant power supply. (Photo courtesy of Dave MacNair.)

When Dave MacNair reached out for a handshake the other day, he apologized for his stained palms and fingers.

"I was gluing wood together, and I got it all over my hands," explained MacNair, who has been a fixture in SLAC's Power Conversion Department for 20 years. The electrical engineer said he had been building a gazebo for his backyard over the weekend, one of many home improvement projects he's tackled, besides tiling his kitchen and landscaping his yard.

"I'm happier being hands-on," MacNair said, this time referring to his role as an electronics designer and engineer at SLAC. He bought his first electronics kit when he was twelve years old, and still has the voltmeter he built with it. Since then, he has been designing and building electronics.

"I like to have the ability to do a design on a blank sheet of paper, rather than building off of something that already exists," MacNair said. Although he said it's been a challenge keeping up with rapidly evolving circuit boards and programming languages, he has stayed at the forefront of accelerator engineering, from his initial work with the Stanford Linear Collider, or SLC, to his current project designing power supplies for future accelerators.

MacNair said he's proud of the progress that the Power Conversion Department has made in pushing power supplies to higher and higher standards of reliability. He recalled dreading the daily 8:15 a.m. meetings at the SLC, when physicists regularly complained of unstable magnet power.

"I judge our success by how little we get mentioned at meetings now," he said with a smile. Steadying the power supply to SLC magnets led to a vast improvement in stability for later projects like the Final Focus Test Beam, the PEP-II collider, and finally the Stanford Synchrotron Radiation Lightsource and the Linac Coherent Light Source. Equipped with the latest technology to precisely control the power flow, these two facilities run steady and strong, allowing MacNair to concentrate on even more advanced projects.

Having made huge gains in power stability, MacNair wants to push reliability, a key concern for accelerator power supplies that will grow more massive and complex alongside the machines they drive. To that end, MacNair is working on a power supply that always keeps the right amount of current coursing to an accelerator's steering and focusing magnets, even if one of the supply's own components fails.

"It's redundant, which means that if something requires n systems, you put in one extra," MacNair said. He completed a prototype of the supply last month. Now it powers a test apparatus in Building 15. So far it has handled simulated failures with panache. MacNair will fly to Vancouver late this week to present the work at the 2009 Particle Accelerator Conference, a showcase for the latest accelerator technology.

"People are always looking for new ideas," he said. "My goal is to get the information out, so that there's interest and demand to carry the project into production of systems."

The desire to learn about and share new technology has taken MacNair to accelerators and lightsources around the United States and the world, including Fermilab, England's Diamond lightsource and CERN. His work too has journeyed internationally; a first- generation model of his reliable power supply is currently powering the Accelerator Test Facility 2 at KEK, the Japanese high-energy physics lab.

Striving toward novel solutions for accelerator power keeps MacNair's handsóand brainóbusy. Maybe that's why he still finds his daily work as exciting as soldering together his first voltmeter.

"It's quite challenging," he said. "I need to draw on a lifetime of experience to solve the unique technical problems at SLAC."

óLauren Schenkman
SLAC Today, April 29, 2009