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RHIC PROGRESS AND FUTURE
Brookhaven National Laboratory, Upton, NY 11973, USA
The talk reviews RHC performance, including unprece-
dented manipulations of polarized beams and recent low
energy operations. Achievements and limiting factors of
RHIC operation are discussed, such as intrabeam scat-
tering, electron cloud, beam-beam effects, magnet vibra-
tions, and the efficiency of novel countermeasures such
as bunched beam stochastic cooling, beam scrubbing and
chamber coatings. future upgrade plans and the pertinent
R&D program will also be presented.
The Relativistic Heavy Ion Collider (RHIC) consists of
two independent storage rings, making it a highly flexi-
ble facility to study collisions of hadron beams ranging
from polarized protons to fully stripped gold ions. Colli-
sions of 100GeV/nucleon gold ions probe the conditions
of the early universe, where quarks and gluons form a new
state of matter. As a polarized proton collider, RHIC pro-
vices unique physics opportunities to study spin effects
in hadronic interactions in high-luminosity proton-proton
collisions at beam energies up to 250 GeV. To preserve
beam polarization on the energy ramp, pairs of full Siberian
snakes are installed on opposite sides of each ring (Fig. 2),
thus avoiding intrinsic and imperfection spin resonances
during acceleration. Two interaction regions around the ex-
periments STAR and PHENIX are equipped with pairs of
spin rotators, which allow manipulation of the polarization
direction at these interaction points.
During its first eight years of operation RHIC has ex-
ceeded its design parameters for gold-gold collisions, and
has successfully operated in an asymmetric, mode collid-
ing deuterons and gold ions. Additionally, record lumi-
nosities were reached in copper-copper collisions. Further-
more, RHC has performed very successfully as a polar-
ized proton collider at 100 GeV beam energy. Fig. I shows
achieved integrated nucleon-pair luminosities for various
modes of operation since 2000.
Polarized proton collisions at 250 Ge V
During Run-9, RHIC provided first polarized proton
collisions at 250 GeV . With spin resonances beyond
100 GeV being being more than twice as strong as those
below 100Gev (Fig. 3), a much more precise control of
machine parameters such as orbits and betatron tunes is
Figure 1: Integrated nucleon-pair luminosity for all RIHC
physics running modes since the start of operation in 2000.
Figure 2: Layout of the RIHIC accelerator complex. Two
Siberian snakes are installed on opposite sides of each ring
to preserve polarization. Spin rotators around the two ex-
periments PHENIX and STAR allow for manipulation of
the spin direction at the collision points.
required to preserve polarization during the acceleration
Achieved polarization levels were 42 percent at top en-
ergy in both rings (Fig. 4), while the average polarization at
injection energy was 55 percent. As polarization measure-
ments during the acceleration ramp indicate, polarization
is preserved up to a beam energy of 100 GeV, while losses
occured around the three strongest intrinsic spin resonances
at 136 GeV, 199 GeV, and 221 GeV. A peak luminosity of
122- 1030 em-2seC1 was achieved.
Low energy Au-Au collisions
Gold-gold collisions at energies of only a few GeV in
the center-of-mass are required to search for the QCD crit-
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Montag,C. RHIC progress and future, article, May 4, 2009; United States. (https://digital.library.unt.edu/ark:/67531/metadc934833/m1/3/: accessed April 22, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.