When the Stanford Linear Collider (SLC) was on the drawing board 20
years ago, it called for klystrons more than twice as powerful as the
existing ones, and needed hundreds of them reliably produced. The
Klystron/Microwave Department developed the new klystron, known as the
5045, and was soon producing them at a rate of 12 per month.
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A 5045 Klystron is shown here along with the people
who were responsible for its production and testing.
(Photo by Diana Rogers) |
"At the time there was real concern that the success of the SLC project
might be jeopardized if these new high power klystrons could not be
reliably manufactured," said Chris Pearson, who heads the department’s
manufacturing group. "Today it is clear that the 5045 design and
production is a real success story."
Stationed every 40 feet along the Klystron Gallery, the 5045 klystrons
supply radio frequency (RF) power to the accelerator beam
at regular intervals, increasing its energy from a few thousand electron
volts to about 50 million by the end of the linear accelerator (linac).
The department’s modern manufacturing facility currently makes one to
two klystron tubes a month to replace old or failing tubes among the
roughly 240 that power the linac. The average running time between
failures is now 70,000 hours, nearly double original lifetime predictions.
Several klystrons are operating with over 100,000 accumulated hours
(equivalent to more than 11 years of continuous running).
"Our production yield is also extraordinary," said Pearson. In the last
three years, 100 percent of klystrons produced met all requirements at
final testing; the figure is 96 percent over 10 years. It’s unparalleled
in this country’s klystron industry.
The 5045 klystrons are 6 .-high vacuum tubes, containing hundreds of
components fabricated from copper, stainless steel and ceramic. They
generate 3.5 microsecond, 67 megawatt. pulses of microwave energy, (more
than five times the power of any military or commercial tubes produced in
the US).
Inside the klystron, an electron gun emits a beam of electrons that
travels through six copper cavities. Each cavity resonates to support an
electric field that creates a series of tightly bunched electrons. The
last cavity transforms the electrons’ kinetic energy into microwave (RF)
energy. This power travels through a waveguide (a copper tube) to the
accelerator where it boosts the energy of the electron beam.
"Although the whole thing is one big electronic device—an RF amplifier
—there are no wires, chips or circuit boards inside. Manufacturing these
klystrons is essentially a mechanical problem, requiring careful attention
to materials, precision machining, and vacuum processing," said Pearson,
whose group uses rigorous quality control, which is necessary to create
and preserve the ultra-high vacuum inside each klystron that prevents
arcing damage to the tube.
