588
K. Hübner et al.
electron cooling to decrease the transverse emittance of the accumulated beam. The
CPS provides a total of 8 × 10 10 ions per pulse in four bunches.
The acceleration cycles for the different users are grouped in a supercycle
depending on the user requirements allowing for a quick, reproducible switching
from one to another mode of operation [11].
10.1.2 Brookhaven Alternating Gradient Synchrotron (AGS)
After successful completion of the 3 GeV Cosmotron in 1952 the design study for
a more powerful accelerator was launched coincident with the invention of the
alternating-gradient principle [12, 13]. Construction led by G.K. Green and J.P.
Blewett started in 1953 and commissioning was completed with the first proton
beam accelerated to 31 GeV in July 1960 [14]. In order to test experimentally
whether the beam would pass transition energy, an electron analogue had been
built in 1954 and operated until 1957. This model had a circumference of 43.1 m
accelerating electrons from 1 to 10 MeV with transition energy at 3.5 MeV. In
order to reduce cost, the alternating-gradient, strong-focusing was provided by
electrostatic lenses and bending by electrostatic fields [15]. The test showed that
transition can be crossed without problems but the price was a delay in the AGS
construction relative to the CERN PS, which however was at the end compensated
by better preparation of the experimental programme compared to CERN.
The first injector was a 50 MeV Alvarez-type proton linear accelerator. The
present 200 MeV linear accelerator began operation in 1970. In 1982 H − charge
exchange injection into the AGS was introduced [16] and in 1991 a 1.5 GeV booster
synchrotron was commissioned [17]. The Booster can provide 1.5 × 10 13 protons
per pulse at 1.9 GeV at the design repetition frequency of 7.5 Hz. The acceleration
harmonic schemes (Booster harmonic, AGS harmonic, transfers) evolved from (3,
4, 12) to (2, 4, 8) and finally to (1, 6) in pursuit of higher intensity [18] (Table 10.3).
Secondary beams from the AGS were initially provided from internal targets.
This also creates high beam loss and activation in the accelerator not compatible
with high-intensity operation. The first fast-extraction was installed in the mid-60s
followed by slow-extraction in 1967 which served up to six target stations and
spilling out protons with repetition periods from 1.8 s to 5.8 s. To cope with the
intensity increases, the AGS underwent a series of upgrades including a new main
magnet power supply, addition of transverse feed-back, special magnets to provide
fast crossing of the transition energy, and a high power RF system [20]. In the early
2000s the AGS provided a slow-extracted beam of 7 × 10 13 protons per pulse at
24 GeV [21].
With the appropriate source added to the 200 MeV linear accelerator, polarized
protons have been produced by the injector chains from 1985 onward for fixed target
experiments. To meet injector requirements for RHIC—intensity and polarization—
the polarized source underwent a major upgrade [22]. The polarization transmission
efficiency in the AGS has been substantially improved with the installation of two
K. Hübner et al.
electron cooling to decrease the transverse emittance of the accumulated beam. The
CPS provides a total of 8 × 10 10 ions per pulse in four bunches.
The acceleration cycles for the different users are grouped in a supercycle
depending on the user requirements allowing for a quick, reproducible switching
from one to another mode of operation [11].
10.1.2 Brookhaven Alternating Gradient Synchrotron (AGS)
After successful completion of the 3 GeV Cosmotron in 1952 the design study for
a more powerful accelerator was launched coincident with the invention of the
alternating-gradient principle [12, 13]. Construction led by G.K. Green and J.P.
Blewett started in 1953 and commissioning was completed with the first proton
beam accelerated to 31 GeV in July 1960 [14]. In order to test experimentally
whether the beam would pass transition energy, an electron analogue had been
built in 1954 and operated until 1957. This model had a circumference of 43.1 m
accelerating electrons from 1 to 10 MeV with transition energy at 3.5 MeV. In
order to reduce cost, the alternating-gradient, strong-focusing was provided by
electrostatic lenses and bending by electrostatic fields [15]. The test showed that
transition can be crossed without problems but the price was a delay in the AGS
construction relative to the CERN PS, which however was at the end compensated
by better preparation of the experimental programme compared to CERN.
The first injector was a 50 MeV Alvarez-type proton linear accelerator. The
present 200 MeV linear accelerator began operation in 1970. In 1982 H − charge
exchange injection into the AGS was introduced [16] and in 1991 a 1.5 GeV booster
synchrotron was commissioned [17]. The Booster can provide 1.5 × 10 13 protons
per pulse at 1.9 GeV at the design repetition frequency of 7.5 Hz. The acceleration
harmonic schemes (Booster harmonic, AGS harmonic, transfers) evolved from (3,
4, 12) to (2, 4, 8) and finally to (1, 6) in pursuit of higher intensity [18] (Table 10.3).
Secondary beams from the AGS were initially provided from internal targets.
This also creates high beam loss and activation in the accelerator not compatible
with high-intensity operation. The first fast-extraction was installed in the mid-60s
followed by slow-extraction in 1967 which served up to six target stations and
spilling out protons with repetition periods from 1.8 s to 5.8 s. To cope with the
intensity increases, the AGS underwent a series of upgrades including a new main
magnet power supply, addition of transverse feed-back, special magnets to provide
fast crossing of the transition energy, and a high power RF system [20]. In the early
2000s the AGS provided a slow-extracted beam of 7 × 10 13 protons per pulse at
24 GeV [21].
With the appropriate source added to the 200 MeV linear accelerator, polarized
protons have been produced by the injector chains from 1985 onward for fixed target
experiments. To meet injector requirements for RHIC—intensity and polarization—
the polarized source underwent a major upgrade [22]. The polarization transmission
efficiency in the AGS has been substantially improved with the installation of two