750
M. Dohlus et al.
linac proton beam, of 3 (π) mm mr, full un-normalised (y, x) emittances, F = 20,
two-plane painting, a 450 (π) mm mr, ring vertical acceptance, and 150 and 300
(π) mm mr, respective, full un-normalised (y, x) ring emittances. These allow 75
10 +12 protons to be injected in 172 μs over 250 turns, at a peak space charge tune
shift ≈0.23 and a 1.08 MW beam power. ISIS second harmonic cavities may be
used at a h = 2, frequency range of 2.91–3.45 MHz.
11.4.3.4 Direct Proton Injection from a Pulsed Proton Linac to a Pulsed
Compressor Ring
A compressor ring and a RCS may be compared for the case of direct proton
injection and equal beam powers. The compressor ring requires a higher energy,
longer, more costly proton linac injector, a little larger ring circumference, slightly
smaller ring acceptances, and a simpler, lower power radio frequency system. A
detailed cost estimate for both linacs and rings is needed in order to determine the
choice.
11.4.3.5 Direct Proton Injection from a Pulsed Proton Linac to a Fast
Cycling FFAG Ring
FFAG accelerators have non-linear fields and focusing, defined by B = Bo (1 +
x/r o ) K , with x and r the distances from the ring centre and K = ρ r (B /B ρ) =
ρ r Kv. They may be non-scaling or scaling (NSFFAG or SCFFAG) [134, 135],
with the former more common for higher beam energies. Two types have been
considered for a 26.0 m radius ISIS upgrade. One, proposed by S. Machida [136],
has a novel type of DF spiral lattice cell and construction of a model magnet cell is
under study.
The second, by G.H. Rees [134], has 12 [O f(+) o D(–) o F(+) o D(–) o f(+)
O] pumplet cells, where the non-linear magnets, d & D, give vertical focusing
(horizontal defocusing), the f & F provide opposite polarity focusing, straight
sections are O and o and bend directions are (+) or (–), with (–) the reverse
bends.
Ring closed orbits needed for direct, multi-turn, proton injection into the FFAG
are influenced by the non-linear main fields. Injection orbit bumps reduce the ring
periodicity below that set by the number of lattice cells, and the design must ensure
the beam dynamic aperture is not reduced during the injection.
FFAG-RCS differences include the former’s lower chromaticities and beam-size
dependent tune shifts and the latter’s lower injection dispersion. Errors in FFAG’s
non-linear magnets are harder to correct than those in RCS’s linear magnets. A
RCS has the advantage of no reverse bends so, in the case of equal outer radii,
room temperature magnets, it may have a higher energy and beam power than a
FFAG. It may also include trim quadrupoles, sextupoles and octupoles to adjust
M. Dohlus et al.
linac proton beam, of 3 (π) mm mr, full un-normalised (y, x) emittances, F = 20,
two-plane painting, a 450 (π) mm mr, ring vertical acceptance, and 150 and 300
(π) mm mr, respective, full un-normalised (y, x) ring emittances. These allow 75
10 +12 protons to be injected in 172 μs over 250 turns, at a peak space charge tune
shift ≈0.23 and a 1.08 MW beam power. ISIS second harmonic cavities may be
used at a h = 2, frequency range of 2.91–3.45 MHz.
11.4.3.4 Direct Proton Injection from a Pulsed Proton Linac to a Pulsed
Compressor Ring
A compressor ring and a RCS may be compared for the case of direct proton
injection and equal beam powers. The compressor ring requires a higher energy,
longer, more costly proton linac injector, a little larger ring circumference, slightly
smaller ring acceptances, and a simpler, lower power radio frequency system. A
detailed cost estimate for both linacs and rings is needed in order to determine the
choice.
11.4.3.5 Direct Proton Injection from a Pulsed Proton Linac to a Fast
Cycling FFAG Ring
FFAG accelerators have non-linear fields and focusing, defined by B = Bo (1 +
x/r o ) K , with x and r the distances from the ring centre and K = ρ r (B /B ρ) =
ρ r Kv. They may be non-scaling or scaling (NSFFAG or SCFFAG) [134, 135],
with the former more common for higher beam energies. Two types have been
considered for a 26.0 m radius ISIS upgrade. One, proposed by S. Machida [136],
has a novel type of DF spiral lattice cell and construction of a model magnet cell is
under study.
The second, by G.H. Rees [134], has 12 [O f(+) o D(–) o F(+) o D(–) o f(+)
O] pumplet cells, where the non-linear magnets, d & D, give vertical focusing
(horizontal defocusing), the f & F provide opposite polarity focusing, straight
sections are O and o and bend directions are (+) or (–), with (–) the reverse
bends.
Ring closed orbits needed for direct, multi-turn, proton injection into the FFAG
are influenced by the non-linear main fields. Injection orbit bumps reduce the ring
periodicity below that set by the number of lattice cells, and the design must ensure
the beam dynamic aperture is not reduced during the injection.
FFAG-RCS differences include the former’s lower chromaticities and beam-size
dependent tune shifts and the latter’s lower injection dispersion. Errors in FFAG’s
non-linear magnets are harder to correct than those in RCS’s linear magnets. A
RCS has the advantage of no reverse bends so, in the case of equal outer radii,
room temperature magnets, it may have a higher energy and beam power than a
FFAG. It may also include trim quadrupoles, sextupoles and octupoles to adjust