Wednesday - September 29, 2010
SLAC Today is
available online at:
http://today.slac.stanford.edu
In this issue:
People: The Light Machine Shop Does Some Heavy Lifting
A Flippy Way to Tell Which Way is North
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Wednesday - September 29, 2010 |
People: The Light Machine Shop Does Some Heavy Lifting Brian Duda consults with Craig Jordan about a Super Cryogenic Dark Matter Search part. (Photo
by Lori Ann White.)
It's pushing 3 p.m.—time to clock out in less than an hour—and design engineer Brian Duda appears in the machine shop office with two foil-wrapped parts that need tweaking. He bends over them in consultation with floor supervisor Craig Jordan, who's holding down the fort while the shop's manager, Denise Larsen, is out. The parts are needed for fabrication of the germanium crystals that form the heart of the Super Cryogenic Dark Matter Search detector. It's a rush job. They're always rush jobs. "He's a popular guy," Duda says of Jordan, who is studying CAD drawings of the parts. "A German guy on the [Linac Coherent Light Source] tried to tip me," Jordan adds. "I had to tell him, 'I can't take money!' But he did ask me out for a beer, later." The two finish their consultation and Duda turns to leave. "Really," he says, tone serious, "these are great guys to work with and very competent." Jordan shrugs off Duda's compliment. "This one will be pretty easy," he says, pointing to a thick, sturdy aluminum ring. "He just needs a little shaved off the top." How much is a little? ".025 of an inch," Jordan says. "About eight human hairs' worth." A Flippy Way to Tell Which Way is North (Photo by Brad Plummer.)
Forget pocket protectors: Flippy magnets are the low-tech tools that some high-tech engineers won't be caught without. The plastic hand-held stick topped with a rotating bar magnet the size of an Advil is a quick, easy way to find out if any of the magnets that steer particles through an accelerator is pointed in the wrong direction—a situation that can send particles flying off-course. At SLAC's Linac Coherent Light Source, for instance, a series of 210 electromagnets steer, compress, and focus a beam of electrons that is used to generate powerful pulses of X-ray laser light. The electron beam can't deviate more than 10 microns as it passes through the magnets, so it's important to get the magnetic fields aligned just right. Unlike the magnets you have on your fridge, an electromagnet works only when turned on. Its north and south poles are determined by the direction a current flows through a coil to create the magnetic field. Reverse the flow of current and the magnet's poles reverse. So in a special lab, engineers turned on each magnet, carefully measured its magnetic field and marked down how its two power cables should be hooked up to get current flowing in the right direction. But then the magnets are transported from the measurement lab to the LCLS tunnel; and once there, the power cables, which are hundreds of feet long, may get hooked up the wrong way. To double-check the connections, an engineer walks the tunnel with a flippy magnet. It flips blue for north or red for south. "It's a nice, quick way of checking the magnets are the right polarity," says Scott Anderson, a SLAC magnet measurements engineer. The magnets-on-sticks can often be found lying around common areas. But lucky are the engineers who get their own. "Not everyone has a flippy magnet," Anderson says. |
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