FFAG for next Light Source

Alessandro G. RuggieroLight Source Workshop

January 24-26, 2007

Jan. 24-26, 2007 A.G. Ruggiero -- Brookhaven National Laboratory 2/18

Components: 10 mA - 3 GeV

Source 3 GeV SC Linac Storage Ring FEL

Brilliance --> Source + Lattice Properties

Source 240 MeV Linac 3 GeV RCS Storage Ring FEL

Damping Time + Quantum Fluctuation

n = 1 π mm-mrad ~ 0.1 π nm

Jan. 24-26, 2007 A.G. Ruggiero -- Brookhaven National Laboratory 3/18

FFAG Rings for Acceleration and Storage

Source 240 MeV 0.24 - 0.56 GeV 0.56 - 1.3 GeV 1.3 - 3 GeV SR FEL

Linac FFAG’s

Synchrotron Radiation is from Ring Bending.

Beam Brilliance is determined originally by the Source

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!

Energy

Recovery

Jan. 24-26, 2007 A.G. Ruggiero -- Brookhaven National Laboratory 4/18

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.

An Example of FFAG SR Facility

FFAG-1

FFAG-2

FFAG-3

Linac

Jan. 24-26, 2007 A.G. Ruggiero -- Brookhaven National Laboratory 5/18

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 6/18

Considerations of FFAG

FFAGFFAG accelerators are an old technology proposed and demonstrated about a half a century 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, 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 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 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 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 acceleration was also considered problematic over such a large momentum aperture. Moreover, the

FFAGFFAG accelerator was always coupled to the need of a relatively large injection energy (of few 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 hundred MeV) at one end, and the need of stacking/accumulating device at the other end of the

accelerating cycle.accelerating cycle.

Recently, there is a renewed interest in Recently, there is a renewed interest in FFAGFFAG accelerators, first of all because of the accelerators, first of all because of the

practical demonstration of a 150-MeV proton accelerator at KEK, Japan, and secondly because of a 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 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 innovative ideas concerning momentum compaction and magnet dimensions. Because of these more

recent development, recent development, FFAGFFAG accelerators are presently a very appealing and competitive technology accelerators are presently a very appealing and competitive technology

that can allow a beam performance at the same level of the other accelerator architectures.that can allow a beam performance at the same level of the other accelerator architectures.

FFAGFFAG Accelerators have also been extensively studied as possible storage and accelerators Accelerators have also been extensively studied as possible storage and accelerators

of intense beams of Muons and Electrons in the several GeV energy rangeof intense beams of Muons and Electrons in the several GeV energy range

Jan. 24-26, 2007 A.G. Ruggiero -- Brookhaven National Laboratory 7/18

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 withB = 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 8/18

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

g g

S/2 S/2

Injection

Extraction

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 9/18

Staging

FFAG-1 FFAG-2 FFAG-3

Inj. Energy, MeV 240 560 1300Top Energy, MeV 560 1300 3000E/E, ±% 39.95 39.76 39.53

The project can be easily staged

Phase 1 240 MeV Linac + FEL-1Phase 2 add FFAG-1 to 0.56 GeV + FEL-2Phase 3 add FFAG-2 to 1.3 GeV + FEL-3Phase 4 add FFAG-3 to 3.0 GeV + FEL-4

No need for additional Storage Ring as each ring can be operated as such at any energy, for instance at the end

Jan. 24-26, 2007 A.G. Ruggiero -- Brookhaven National Laboratory 10/18

Geometry & Field Profiles

Same for all 3 Rings Injection Top

Circumference, m 807.091807.717No. of Periods 136Period Length, m 5.9345

5.9392Arc Length F-sector, m 0.7 0.697Arc Length D-sector, m 1.4 1.409Short Drift, g, m 0.3Long Drift, S, m 2.5 FFAG-1 FFAG-2 FFAG-3kG

cm

Jan. 24-26, 2007 A.G. Ruggiero -- Brookhaven National Laboratory 11/18

Radial Aperture - Lattice Functions

x, cm

s, m

Jan. 24-26, 2007 A.G. Ruggiero -- Brookhaven National Laboratory 12/18

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 13/18

Period Layout (136 Cells)

Side View

Diagnostic & Steering Boxes

D-Sector Magnet

F-Sector Magnets

Flanges & Bellows

Vacuum Pump

10 cm

Top View

D-Sector Magnet

F-Sector Magnets

Flanges & Bellows

Vacuum Pump

20 cm

Diagnostic & Steering Boxes

RF Cavity

Diagnostic & Steering Boxes

D-Sector Magnet

F-Sector Magnets

Vacuum Pump

6.0 m

50-100 k$

300-600 k$

Jan. 24-26, 2007 A.G. Ruggiero -- Brookhaven National Laboratory 14/18

F and D Arrangement

G > 0 G < 0

B > 0

B < 0

Inj. Ejec. B < 4 kG

F D F

Jan. 24-26, 2007 A.G. Ruggiero -- Brookhaven National Laboratory 15/18

Acceleration

Harmonic Number 1350Number of Bunches 675Total Number of e 1013

e / Bunch 1.5 x 1010 (2.4 nC)Average Current 0.65 AmpRF Frequency 501.454 -->

501.053 MHzRev. Frequency 0.371 MHzRev. Period 2.69 µsRF Phase 60o

Vpeak 1.0 2.3 5.5 MVolt

Acceleration Period 1 msNumber of Revolutions 370

Jan. 24-26, 2007 A.G. Ruggiero -- Brookhaven National Laboratory 16/18

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/dphot./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 17/18

FFAG-3 as Storage Ring at 3 GeV

The Storage Period 4 ms is smaller than Damping Time 9.5 msNo Quantum Fluctuation Effects !!

Take advantage of the low emittance of a good e-sourcesource ~ 0.1 nm

Storage

4 ms

(5 ms)

Acceleration

1 ms

Energy Recovery

That requires deceleration maybe in the same FFAG rings

Rep Rate 200 Hz

Duty Cycle 80%

Or use SR for 100% d.c.

Jan. 24-26, 2007 A.G. Ruggiero -- Brookhaven National Laboratory 18/18

eRHIC: 10-GeV e x 250-GeV p or 100-GeV/u Au

RHIC

10-GeV e-SCLER

Source

RHIC

1-GeV e-SCL

ER

10-GeV ASRSource

RHIC

1-GeV e-SCL

ER

10-GeV FFAG’s (+ SR)Source