A fast injection kicker system for the Tevatron Page: 1 of 3
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FERMILAB-Conf-01/150-E July 2001
A FAST INJECTION KICKER SYSTEM FOR THE TEVATRON
C. Jensen, R. Reilly, B. Hanna, Fermilab*, Batavia IL USA 60510
A new proton injection kicker system is required for
the Tevatron in the Run II era. The new system was
designed to supply 1.25 kG-m into a magnetic aperture of
48 mm vertical x 71 mm horizontal x 5 m long with a
396 ns bunch spacing. The system was designed to be
upgraded to 132 ns bunch spacing with additional pulse
supplies. The system design tradeoffs needed to meet these
goals will be discussed. These include the system
topology, the system impedance and the number of
magnets. This system has been installed in the Tevatron.
The Tevatron for Run II requires 36 proton x 36 pbar
bunch stores with a 396 ns bunch spacing. The protons
are injected as 4 bunches during a 1.25 us flattop, with a
375 ns rise time. This is done 9 times with a gap of 2.6
us left at the end for the abort kicker rise time. The pbar
injection kicker was successfully upgraded in 1995 to
perform the above injections for pbars. To allow for even
higher luminosity, it was decided to build the proton
injection kicker with the capability of 132 ns bunch
spacing (112 ns rise time). This was done by installing
five magnets in the lattice; fewer could have been used to
meet to initial rise time requirements. These shorter
magnets are now powered as two systems, with two in
series and three in series. When the shorter bunch spacing
is needed, additional power supplies will be added and all
the magnets will be individual powered.
2 SYSTEM DESIGN
Once the physics specifications had been set for kick
strength and aperture, several different power supply and
magnet configurations where investigated. The three
parameters that needed to be defined were the topology of
the system, the impedance of the system and the number
of magnets in the Tevatron lattice.
The most common way to operate a kicker system is
with a single pulse supply and an unbalanced magnet. In
that case, the magnetic material is C shaped and one of the
magnet conductors connects to the pulse supply common
and magnet case. In a balanced kicker system there are two
pulse supplies and a balanced magnet. Each conductor of
the magnet is connected to a pulse supply and the
commons of the pulse supplies are connected to the
magnet case. The magnetic material completes surrounds
both conductors; the air gap is between the conductors. In
this way each pulse supply provides energy to fill half of
the air gap with magnetic field. The magnet fill time can
be reduced by 50% over an unbalanced system of the same
impedance  if both supplies are connected at the same
end and two load resistors are connected at the other.
Fermilab is operated by University Research Association Inc. under
Contract No. DE-AC02-76CH03000
Essentially, twice the peak power is supplied to fill the air
gap with magnetic energy. This balanced system was also
used for the pbar injection kicker upgrade in 1995 .
There were constraints on the impedance of the system.
First, the impedance needed to be a sub-multiple of our
standard 50 92 high voltage cable, Times  #AA-5966.
This cable would be used in 182 m lengths for the pulse
forming line and 39 m lengths to connect the pulse
supply to the magnet. Second, for long lifetime, the
AA-5966 cable and the Isolation Design connectors have
a maximum voltage of -65 kV. Finally, the thyratron
enclosure parasitics and thyratron turn on characteristics
have an impact on performance through the choice of
impedance. In the simple approximation that the thyratron
has a practically instantaneous turn on and is simply an
equivalent series inductance, then clearly, a higher system
impedance gives a faster rise time. However, this
approximation is very poor with fast rise times.
Given these parameters and constraints, 16.7 2 and
12.5 92 systems were investigated further. While the
16.7 0 system assumed a single (unbalanced) pulsed
supply, the 12.5 92 system assumed two (balanced)
positive and negative pulse supplies because of the longer
magnet fill time. SPICE was used to model simplistic
systems to determine magnetic field rise time. In addition,
the length of individual magnets was varied from 1 m to
1.6 m; this varied the number of magnets from three to
five. A balanced system with an impedance of 12.5 Q and
a magnet length of 1 m was required to meet the rise time
specification of 113 ns. A peak current of 1600 A and a
charging voltage of 40 kV were required to get the kick
Although the system impedance and topology were
determined, there was considerable uncertainty in
achieving the power supply and magnet performance. The
thyratron and enclosure required a maximum rise time of
42 ns (1% - 99%). The magnet required a 70 ns fill time
with low dispersion. Significant money and effort were
spent to build prototypes starting three years before
operation was required. Since the magnet is covered in a
companion paper , the remainder of this paper will
focus on the power supply.
2.1 Thyratron Enclosure Design
The first decision was the kind of switch. The repetition
rate is 36 shots spaced approximately 4 seconds apart once
every 8 hours for 36 x 36 operation. Many more shots
will be used during tune up. So, this system was designed
for a 10 year lifetime of 10^5 shots. In the pbar kicker
system, spark gaps were used as switches. However, the
proton system requires 10 times the lifetime and only half
the current of the pbar system, so a thyratron was chosen.
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Chris C. Jensen, Robert E. Reilly and Bruce M. Hanna. A fast injection kicker system for the Tevatron, article, July 25, 2001; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc716795/m1/1/: accessed August 14, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.