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ACCELERATING CAVITIES FOR BOOSTER SYNCHROTRON AND INDUS-1 STORAGE RING
RF Cavity for Booster
The booster synchrotron receives electrons from Microtron at
energy level of 20 MeV. These electrons are bunched and accelerated to 450 MeV,
for injection into Indus-1 storage ring, by this RF cavity. The resonant
frequency of this reentrant type cavity is 31.6 MHz and it operates at a vacuum
level of 1.0E-06 mbar.
This was the first large
sized RF cavity realized in RRCAT. Its diameter is 840 mm and length is 600 mm.
It is made of Aluminium Alloy. One of its end plates can be deflected with the
help of a
mechanism
for offline tuning of the cavity. There are three tuning plungers and each has a
tuning range of about 20 kHz, which is sufficient for the operational
requirements.
In the
picture you see the Aluminium cavity, a tuner on the horizontal port and the
power coupler on the vertical port, at the top. The cooling tubes attached to
the end plates are also visible.
RF Cavity for Indus-1
Indus-1
is a 450 MeV, 100 mA electron storage ring, constructed at Centre for Advanced
Technology, Indore, India. The Synchrotron Storage Ring Indus-1, requires one
radio frequency cavity operating at 31.613 MHz. The required RF cavity has been
indigenously designed and developed. The cavity is made of stainless steel and
it is internally electroplated with copper. The copper coating provides low
electrical resistivity for RF currents, which flow on the internal surfaces.
Considering the relatively low frequency of the cavity and the limits suggested
by mechanical design, a re-entrant type of structure was designed. The cavity
has an internal diameter of 840 mm and length of 600 mm. A length of 900 mm is
allotted for the cavity in the ring. The re-entrant cavity structure employs big
"capacitor disks" at 10 mm from the median plane which are attached to the end
plates through 290 mm long "drift tubes".
The
cavity is made in two halves having a large joint at the median plane (normal to
the axis) sealed by a Helicoflexâ seal.
IMA
Section carried out structural design & design of the cooling circuit, design
of coarse & fine tuning systems, FEM analysis of temperatures & thermal
deformations, design for manufacturing and assembly, vacuum testing and the problem solving required during manufacturing.
IMA
Section was deeply involved in the manufacturing, electroplating,
assembly, vacuum testing, RF testing and integration in the ring.
The
cavity is now working in the ring, with a vacuum level of 1.0E-8 mbar with beam.
The total thermal detuning is less that 50 kHz at 22 kV, which is well within
the on-line tuner range, and start-up time is 10 minutes.
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