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Planned Downtime at B-factory Extended to Fix Magnet

(Photo - BaBar)The planned one-week shutdown of PEP-II and BaBar has been unexpectedly extended a week to repair and reinstall a damaged magnet.

The Accelerator Systems Division had planned the downtime to take care of a vacuum leak near the interaction region where particles collide. To prepare for the work, everything near the interaction region was powered off. However, one of the quadrupole magnets did not shut down properly. When the cooling water to the magnets was turned off on May 1, that magnet overheated, charring the coils inside. Crews turned the cooling water back on, but the magnet was already damaged, and the heat caused water to leak into the BaBar detector. All daily system checks so far show the detector is in good working order.

Technicians and accelerator physicists have been taking double shifts to resolve the problem. On May 7, they removed the magnet from the DIRC tunnel—inside the detector three to five meters before the collision point. Getting it out was tricky: crews removed the top half of the damaged magnet, the beam pipe through it, and the bottom half of the magnet, as well as the top half of the other magnet in the DIRC tunnel and its section of beam pipe.

The Mechanical Fabrication Department put spare coils into the magnet and the Magnetic Measurements Group started testing it yesterday. The coils conduct current to create the magnetic field that steers the beam. The Accelerator Systems Division hopes to reinstall the fixed magnet today, and return PEP-II and BaBar to regular operations early next week.

—Heather Rock Woods, May 9, 2007

Ramiro Reyna works in the DIRC tunnel inside the BaBar detector next to the spot where crews removed a damaged quadrapole magnet. (Photo courtesy Diana Rogers.)