New corrector system for the Fermilab booster Page: 1 of 3
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NEW CORRECTOR SYSTEM FOR THE FERMILAB BOOSTER*
E.J. Prebys#, C.C. Drennan, D.J. Harding, V. Kashikhin, J.R. Lackey, A. Makarov, W.A. Pellico
FNAL, Batavia, IL 6060510, U.S.A.
We present an ambitious ongoing project to build and
install a new corrector system in the Fermilab 8 GeV
Booster. The system consists of 48 corrector packages,
each containing horizontal and vertical dipoles, normal
and skew quadrupoles, and normal and skew sextupoles.
Space limitations in the machine have motivated a unique
design, which utilizes custom wound coils around a 12
pole laminated core. Each of the 288 discrete multipole
elements in the system will have a dedicated power
supply, the output current of which is controlled by an
individual programmable ramp. This paper describes the
physics considerations which drove the design, as well as
issues in the control of the system.
The Fermilab Booster  is rapid cycling synchrotron
which accelerates protons from the 400 MeV injection
energy to 8 GeV in 33 msec, at up to 15 Hz. It has a 24
fold periodicity, with each period consisting of four
combined function magnets and two straight sections, as
shown in Figure 1. The "long straight" sections
correspond to beta maxima in the vertical plane and beta
minima in the horizontal, and the "short straight" sections
are the complement.
"short straight" package
- Iiorzota l nimaxirimm
- vertical t minimum SFCTTni ,[ N
F-MAGPET D-MAGNET - . - . D-MAGNET F-MAGNET
long straght package:
-horzonmi f mm rjn
-vertical f m
Figure 1: One of the 24 periods of the Booster
The Fermilab neutrino program places unprecedented
demands Booster, which has not changed significantly
since it was built more than 35 years ago. In particular,
the corrector system is currently not adequate to control
beam position and tune throughout the acceleration cycle,
and provides limited compensation for higher order
EXISTING CORRECTION SYSTEM
The present corrector system dates back to the
construction of the Booster. It comprises 48 corrector
packages, each containing a horizontal and vertical dipole
magnet, as well as a normal and skew quadrupoles. In
general, the correctors are grouped according to the lattice
functions. The 24 at the long straight sections primarily
*Work supported under DOE contract DF-AC02-76CH03000
affect the vertical plane, while the 24 at the short straight
sections primarily affect the horizontal. There is a two
dimensional beam position monitor (BPM) at or near the
location of each corrector element.
There is individual time dependent control of the
dipoles corresponding to the local high beta plane (i.e.
vertical at the long straights and horizontal at the short
straights), while the other dipole at each section is
operated DC and primarily controls the position at
Beam position is controlled by adjusting currents in
corrector sets according to ratios calculated to localize the
beam displacement - generally "3-bumps". For the
correctors with time dependent current, we implement
these adjustments at discrete time breaks during the
acceleration cycle. For example, we can adjust the
position of the beam at a particular point at 10 ms into
acceleration. The currents linearly interpolate between
these discrete time breaks.
There is also a prototype version of a closed orbit
application, which can calculate the optimum set of
corrector currents to reproduce a desired orbit. The
efficacy of this program is currently limited by the
capabilities of the present corrector system, but it serves
as a prototype for control of the new corrector system.
The quadrupole elements have individual DC levels to
which common ramps are added. The ramps are
implemented in four groups: long normal, long skew,
short normal, and short skew. Generally speaking, the
ramped terms correct for tune and coupling through the
cycle, while the DC values compensate for harmonic
content. To this end, a harmonic application can calculate
and apply a DC offset the ith element of the form
Ani = An sin n 01 +9p) (1)
Where n is any integer, O is the normalized phase
advance of element i, and An and C,2 are "knob-able"
parameters. These offsets are additive for arbitrary
combinations of values of n.
In addition, there is a system of sextupoles at discrete
locations around the ring. Sextupoles at the odd numbered
short periods control horizontal chromaticity, while
groups at long periods 4, 10, and 18 control vertical
chromaticity. In addition, combinations of normal and
skew sextupoles at long straights 4, 5, 6, and 7 are
configured to cancel specific third order resonances.
Sextupoles are controlled in a manner similar to the
quadrupoles, although the options for harmonic correction
obviously more limited.
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Prebys, E.J.; Drennan, C.C.; Harding, D.J.; Kashikhin, V.; Lackey, J.R.; Makarov, A. et al. New corrector system for the Fermilab booster, article, June 1, 2007; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc884567/m1/1/: accessed November 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.