By Anna Gosline
Researchers at SLAC work tirelessly to illuminate the mysteries of our
universe, but it takes the hard work of the SLAC Vacuum Group to keep
things crystal clear. Proper functioning of the linear accelerator and
PEP-II requires pressures a billion times lower than atmospheric pressure
and a spotlessly clean vacuum vessel. With over 20 miles of vacuum
chambers, there is a constant need for maintenance and improvement. Thanks
to the hard work of Vacuum Group technicians, physicists and supervisors,
particle beams can speed their way unhindered to new discoveries in high
The vacuum group is an integral part of SLAC.
(Photo by Kelley
Creating optimal pressures along the linac and PEP-II requires an
intimate knowledge of the entire system. Physicists in the Vacuum Group
are constantly looking for new technologies to improve and customize
vacuum conditions, a search that has contributed to the outstanding beam
luminosity achieved by PEP-II. "We make sure the vacuum system does not
limit the beam lifetime," says Daniel Wright (AMS), who has been working
with vacuums at SLAC for the past 26 years. From turbo-molecular pumps
that mechanically draw out air specialized ion pumps that charge and bind
unwanted molecules, the Vacuum Group has a device to eliminate pretty much
anything that comes their way.
Introducing new parts into the vacuum system to upgrade or service the
system is, however, a precarious job. Any molecule present in the vessel
can interact with the beam and ruin it. "A single fingerprint becomes a
huge contamination," comments Dave Bostic (MFD), Operations Engineer. All
vacuum parts must go through a rigorous cleaning process. After initial
chemical cleaning, parts are assembled in clean rooms and then ‘baked out’
under high temperature and low pressure to burn off any trace contaminants
and speed the release of absorbed air molecules.
Immaculately cleaned parts are then installed by field technicians, who
must climb down to the belly of the accelerator and expose the delicate
vacuum system to a host of contaminants. Portable clean rooms, or air
showers, keep the dust and grime out of the vessel while technicians
install parts. "The weight of all of our cleanliness effort is on the
technicians shoulders at that point. They do an amazing job," says Bostic.
In addition to the daily operations, many technicians and supervisors
have spent a sleepless night or two down in the linac or PEP-II, searching
for leaks or part failures and fixing them fast. Experiments at SLAC run
24 hours a day and a serious problem with the vacuum system means major
losses of data and money. "We’ve had people down there for three days,
round the clock. It gets hard just to find someone for the next shift,"
says Matt Hayes (MFD), Vacuum Group supervisor.
Despite the long hours and close spaces, the Vacuum Group’s commitment
to innovation, quality and efficiency has consistently provided excellent
vacuum conditions for particle physics research at SLAC. Their work is
challenging and rewarding. "This is a fun place to be," says Hayes. Must
be something in the air.
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