Transcript Proton FFAG Accelerator Work at Brookhaven

FFAG for next Light Source
Alessandro G. Ruggiero
Light Source Workshop
January 24-26, 2007
Components: 10 mA - 3 GeV
Brilliance -->
Source
3 GeV SC Linac
n

Source
Source + Lattice Properties
Storage Ring
FEL
= 1 π mm-mrad
~ 0.1 π nm
240 MeV Linac
3 GeV RCS
Storage Ring
FEL
Damping Time + Quantum Fluctuation
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
2/18
FFAG Rings for Acceleration and Storage
Source 240 MeV
Linac
0.24 - 0.56 GeV
0.56 - 1.3 GeV 1.3 - 3 GeV
SR
FEL
FFAG’s
Synchrotron Radiation is from Ring Bending.
Beam Brilliance is determined originally by the Source
Energy
Recovery
The Ring Lattice can only decrease the Brilliance
Quantum Fluctuation makes the Brilliance even smaller.
The goal is to minimize acceleration and storage time so that the Beam
spends in FFAG’s a period of time smaller than the Damping Time.
FFAG’s have large Momentum and Betatron Acceptance. And are DC!
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
3/18
An Example of FFAG SR Facility
The following is just an example! An actual project can be easily scaled
down from this either way.
The SR Facility is made of 3 Rings having the same circumference and
structure. They are all located in the same tunnel, either on top of each
other, or side-by-side in a concentric fashion.
FFAG-1
FFAG-2
FFAG-3
Linac
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
4/18
FFAG (1)
Fixed-Field Alternating-Gradient (FFAG) Accelerators have the good feature
that the magnets are not ramped as in a Synchrotron, but are kept at
constant field during the acceleration cycle (Cyclotrons). The beam is
injected on a inner orbit, it spirals to the outside as it is accelerated, and it
is extracted from an outer orbit.
Thus the beam can be accelerated very fast, the limitation being set not by
the magnets but by the RF system. In principle it may also be possible to
accelerate a continuous beam.
During the acceleration cycle the beam can be stopped at any intermediate
energy and the cycle switched into a storage mode.
Each one of the FFAG rings is a continuous SR source. SR can also be
extracted during the acceleration though the magnitude and the point of
source will vary radially with energy.
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
5/18
Considerations of FFAG
FFAG accelerators are an old technology proposed and demonstrated about a half a
century ago. They have often been proposed especially in connection of Spallation Neutron Sources.
But, despite a considerable amount of design and feasibility studies, they were never successfully
endorsed by the scientific community, because they were perceived with a too complex orbit
dynamics, a too large momentum aperture required for acceleration, and consequently too expensive
magnets. RF acceleration was also considered problematic over such a large momentum aperture.
Moreover, the FFAG accelerator was always coupled to the need of a relatively large injection energy
(of few hundred MeV) at one end, and the need of stacking/accumulating device at the other end of
the accelerating cycle.
Recently, there is a renewed interest in FFAG accelerators, first of all because of the
practical demonstration of a 150-MeV proton accelerator at KEK, Japan, and secondly because of a
more modern approach to beam dynamics and magnet lattice design, and of some important
innovative ideas concerning momentum compaction and magnet dimensions. Because of these more
recent development, FFAG accelerators are presently a very appealing and competitive technology
that can allow a beam performance at the same level of the other accelerator architectures.
FFAG Accelerators have also been extensively studied as possible storage and accelerators
of intense beams of Muons and Electrons in the several GeV energy range
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
6/18
FFAG Lattice Choices
Scaling Lattice (KEK)
Alternating Field Profile chosen so that all trajectories have same
optical parameters, independent of particle momentum (zero radial
chromaticity) achieved with
B = B0 (r/r0)–n
But very large Physical aperture to accommodate large momentum
range (±30-50%). Large bending field. Limited insertions. Energy
limitation. Expensive. It prefers DFD triplet.
Non-Scaling Lattice (Muon Collaboration)
Alternating Linear Field Profile. Large variation of optic parameters
over required momentum range (Large Chromaticity). But compact
Physical Aperture. Large Insertions. Lower magnetic fields. It prefers
FDF triplets. Large energies possible. Expected to be cheaper.
Scaling lattice has been demonstrated in Japan. Non-Scaling Lattice needs
practical demonstration. Electron Models. EMMA and SBIR.
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
7/18
FDF Triplet
The FFAG we propose here is a Radial-Sector FFAG with Non-Scaling Lattice,
made of an unbroken sequence of FDF triplet where magnets are separated
by short and long drifts. The field in the magnets has a linear profile, as the
magnets are asymmetric quadrupole laterally displaced from each other and
from the reference orbit to be the injection energy.
F
D
F
S/2
Injection
S/2
g
Extraction
g
Most of the bending is done in the central D-magnet. There is a minor
reverse bend in the F-Magnets. The magnet configuration and lattice are
identiacal in the 3 rings.
Each ring can accept an energy spread as large as ±40% measured
from the central energy.
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
8/18
Staging
Inj. Energy, MeV
Top Energy, MeV
E/E, ±%
FFAG-1
FFAG-2
FFAG-3
240
560
39.95
560
1300
39.76
1300
3000
39.53
The project can be easily staged
Phase
Phase
Phase
Phase
1
2
3
4
Jan. 24-26, 2007
No need for additional Storage Ring as
each ring can be operated as such at any
energy, for instance at the end
240 MeV Linac + FEL-1
add FFAG-1 to 0.56 GeV + FEL-2
add FFAG-2 to 1.3 GeV + FEL-3
add FFAG-3 to 3.0 GeV + FEL-4
A.G. Ruggiero -- Brookhaven National Laboratory
9/18
Geometry & Field Profiles
Same for all 3 Rings
Injection
Top
Circumference, m
No. of Periods
Period Length, m
Arc Length F-sector, m
Arc Length D-sector, m
Short Drift, g, m
Long Drift, S, m
807.091
807.717
136
5.9345
0.7
1.4
5.9392
0.697
1.409
0.3
2.5
FFAG-1
FFAG-2
FFAG-3
kG
cm
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
10/18
Radial Aperture - Lattice Functions
x, cm
s, m
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
11/18
Betatron Tunes - Compaction Factor
Circumference Diff. ΔC in cm
vs. Momentum Deviation δ
c
- 9.0x10-5
-
6.0x10-4
H-rad, m
8.24x10-3
-
4.95x10-2
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
12/18
Period Layout (136 Cells)
Diagnostic & Steering Boxes
Flanges & Bellows
D-Sector Magnet
20 cm
Top View
Vacuum
Pump
6.0 m
F-Sector Magnets
50-100 k$
Diagnostic & Steering Boxes
Flanges & Bellows
D-Sector Magnet
10 cm
Side View
Vacuum
Pump
F-Sector Magnets
300-600 k$
Diagnostic & Steering Boxes
D-Sector Magnet
RF Cavity
Vacuum
Pump
F-Sector Magnets
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
13/18
F and D Arrangement F
G > 0
D
F
G < 0
B > 0
B < 0
Inj.
Jan. 24-26, 2007
Ejec.
B < 4 kG
A.G. Ruggiero -- Brookhaven National Laboratory
14/18
Acceleration
Harmonic Number
Number of Bunches
Total Number of e
e / Bunch
Average Current
RF Frequency
Rev. Frequency
Rev. Period
RF Phase
Vpeak
Acceleration Period
Number of Revolutions
Jan. 24-26, 2007
1350
675
1013
1.5 x 1010 (2.4 nC)
0.65 Amp
501.454
-->
501.053 MHz
0.371 MHz
2.69 µs
60o
1.0
2.3
5.5 MVolt
1 ms
370
A.G. Ruggiero -- Brookhaven National Laboratory
15/18
Radiation Performance
FFAG-1
FFAG-2
FFAG-3
Energy, GeV
0.62
1.30
3.00
U0, keV/turn
1.56
30.1
853.7
E, ms
1007
117
9.5
E/E, 10-4
1.29
2.54
5.87
eq, nm
1.7
6.4
33.1
B, kG
0.46
1.0
2.5
, Ao
1054
110
8.3
dN/d
phot./sec/mrad
/mrad/0.1%BW
0.04 x 1014
0.17 x 1014
0.9 x 1014
Brill./Flux, mm-2
1200
310
61
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
16/18
FFAG-3 as Storage Ring at 3 GeV
Acceleration
Storage
1 ms
4 ms
(5 ms)
Rep Rate 200 Hz
Duty Cycle 80%
Energy Recovery
Or use SR for 100% d.c.
That requires deceleration maybe in
the same FFAG rings
The Storage Period 4 ms is smaller than Damping Time 9.5 ms
No Quantum Fluctuation Effects !!
Take advantage of the low emittance of a good e-source
source ~ 0.1 nm
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
17/18
eRHIC: 10-GeV e x 250-GeV p or 100-GeV/u Au
1-GeV e-SCL
10-GeV e-SCL
ER
Source
10-GeV ASR
Source
ER
RHIC
RHIC
1-GeV e-SCL
Source
10-GeV FFAG’s (+ SR)
ER
RHIC
Jan. 24-26, 2007
A.G. Ruggiero -- Brookhaven National Laboratory
18/18