FFAG for next Light Source Alessandro G. Ruggiero Light Source Workshop January 24-26, 2007

Jan , 2007A.G. Ruggiero -- Brookhaven National Laboratory2/18 Components: 10 mA - 3 GeV Source 3 GeV SC LinacStorage 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 , 2007A.G. Ruggiero -- Brookhaven National Laboratory3/18 FFAG Rings for Acceleration and Storage Source 240 MeV GeV GeV GeV SR FEL LinacFFAG’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 , 2007A.G. Ruggiero -- Brookhaven National Laboratory4/18 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 , 2007A.G. Ruggiero -- Brookhaven National Laboratory5/18 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 , 2007A.G. Ruggiero -- Brookhaven National Laboratory6/18 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 , 2007A.G. Ruggiero -- Brookhaven National Laboratory7/18 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 = B 0 (r/r 0 ) –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 , 2007A.G. Ruggiero -- Brookhaven National Laboratory8/18 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/2S/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 , 2007A.G. Ruggiero -- Brookhaven National Laboratory9/18 Staging FFAG-1FFAG-2FFAG-3 Inj. Energy, MeV Top Energy, MeV  E/E, ±% The project can be easily staged Phase 1240 MeV Linac + FEL-1 Phase2add FFAG-1 to 0.56 GeV + FEL-2 Phase 3add FFAG-2 to 1.3 GeV + FEL-3 Phase 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 , 2007A.G. Ruggiero -- Brookhaven National Laboratory10/18 Geometry & Field Profiles Same for all 3 RingsInjectionTop Circumference, m No. of Periods 136 Period Length, m Arc Length F-sector, m Arc Length D-sector, m Short Drift, g, m 0.3 Long Drift, S, m 2.5 FFAG-1 FFAG-2 FFAG-3 kG cm

Jan , 2007A.G. Ruggiero -- Brookhaven National Laboratory11/18 Radial Aperture - Lattice Functions x, cm s, m

Jan , 2007A.G. Ruggiero -- Brookhaven National Laboratory12/18 Betatron Tunes - Compaction Factor Circumference Diff. ΔC in cm vs. Momentum Deviation δ  c - 9.0x x10 -4 H-rad, m 8.24x x10 -2

Jan , 2007A.G. Ruggiero -- Brookhaven National Laboratory13/18 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 k$ k$

Jan , 2007A.G. Ruggiero -- Brookhaven National Laboratory14/18 F and D Arrangement G > 0G < 0 B > 0 B < 0 Inj. Ejec. B < 4 kG F D F

Jan , 2007A.G. Ruggiero -- Brookhaven National Laboratory15/18 Acceleration Harmonic Number1350 Number of Bunches675 Total Number of e10 13 e / Bunch1.5 x (2.4 nC) Average Current0.65 Amp RF Frequency > MHz Rev. Frequency0.371 MHz Rev. Period2.69 µs RF Phase60 o V peak MVolt Acceleration Period1 ms Number of Revolutions370

Jan , 2007A.G. Ruggiero -- Brookhaven National Laboratory16/18 Radiation Performance FFAG-1FFAG-2FFAG-3 Energy, GeV U 0, keV/turn  E, ms  E /E,  eq, nm B, kG , A o dN/d  phot./sec/mrad  /mrad  /0.1%BW 0.04 x x x Brill./Flux, mm

Jan , 2007A.G. Ruggiero -- Brookhaven National Laboratory17/18 FFAG-3 as Storage Ring at 3 GeV 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 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 , 2007A.G. Ruggiero -- Brookhaven National Laboratory18/18 eRHIC: 10-GeV e x 250-GeV p or 100-GeV/u Au RHIC 10-GeV e-SCL ER Source RHIC 1-GeV e-SCL ER 10-GeV ASR Source RHIC 1-GeV e-SCL ER 10-GeV FFAG’s (+ SR) Source