FFAG for next Light Source

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

2. Components: 10 mA - 3 GeV Brilliance --> Source + Lattice Properties Source 3 GeV SC Linac Storage Ring FEL n = 1 π mm-mrad  ~ 0.1 π nm Source 240 MeV Linac 3 GeV RCS Storage Ring FEL Damping Time + Quantum Fluctuation A.G. Ruggiero -- Brookhaven National Laboratory

3. 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 A.G. Ruggiero -- Brookhaven National Laboratory

4. 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 A.G. Ruggiero -- Brookhaven National Laboratory

5. 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. A.G. Ruggiero -- Brookhaven National Laboratory

6. 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 A.G. Ruggiero -- Brookhaven National Laboratory

7. 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. A.G. Ruggiero -- Brookhaven National Laboratory

8. 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. FDF S/2 S/2 Extraction Injection g 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. A.G. Ruggiero -- Brookhaven National Laboratory

9. Staging • FFAG-1 FFAG-2 FFAG-3 • Inj. Energy, MeV 240 560 1300 • Top Energy, MeV 560 1300 3000 • E/E, ±% 39.95 39.76 39.53 • The project can be easily staged • Phase 1 240 MeV Linac + FEL-1 • Phase 2 add FFAG-1 to 0.56 GeV + FEL-2 • Phase 3 add 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 A.G. Ruggiero -- Brookhaven National Laboratory

10. Geometry & Field Profiles • Same for all 3 Rings Injection Top • Circumference, m 807.091 807.717 • No. of Periods 136 • Period Length, m 5.9345 5.9392 • Arc Length F-sector, m 0.7 0.697 • Arc Length D-sector, m 1.4 1.409 • Short Drift, g, m 0.3 • Long Drift, S, m 2.5 • FFAG-1 FFAG-2 FFAG-3 kG cm A.G. Ruggiero -- Brookhaven National Laboratory

11. Radial Aperture - Lattice Functions x, cm s, m A.G. Ruggiero -- Brookhaven National Laboratory

12. 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 A.G. Ruggiero -- Brookhaven National Laboratory

13. Diagnostic & Steering Boxes Flanges & Bellows D-Sector Magnet 20 cm Top View Vacuum Pump F-Sector Magnets Diagnostic & Steering Boxes Flanges & Bellows D-Sector Magnet 10 cm Side View Diagnostic & Steering Boxes Vacuum Pump F-Sector Magnets D-Sector Magnet RF Cavity Vacuum Pump F-Sector Magnets Period Layout (136 Cells) 6.0 m 50-100 k$ 300-600 k$ A.G. Ruggiero -- Brookhaven National Laboratory

14. F and D Arrangement FDF G > 0 G < 0 B > 0 B < 0 Inj. Ejec. B < 4 kG A.G. Ruggiero -- Brookhaven National Laboratory

15. Acceleration • Harmonic Number 1350 • Number of Bunches 675 • Total Number of e 1013 • e / Bunch 1.5 x 1010 (2.4 nC) • Average Current 0.65 Amp • RF Frequency 501.454 --> 501.053 MHz • Rev. Frequency 0.371 MHz • Rev. Period 2.69 µs • RF Phase 60o • Vpeak 1.0 2.3 5.5 MVolt • Acceleration Period 1 ms • Number of Revolutions 370 A.G. Ruggiero -- Brookhaven National Laboratory

16. Radiation Performance A.G. Ruggiero -- Brookhaven National Laboratory

17. 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 Acceleration 1 ms Storage 4 ms (5 ms) Rep Rate 200 Hz Duty Cycle 80% Or use SR for 100% d.c. Energy Recovery That requires deceleration maybe in the same FFAG rings A.G. Ruggiero -- Brookhaven National Laboratory

18. 1-GeV e-SCL 10-GeV e-SCL ER 10-GeV ASR Source Source ER RHIC RHIC eRHIC: 10-GeV e x 250-GeV p or 100-GeV/u Au 1-GeV e-SCL 10-GeV FFAG’s (+ SR) Source ER RHIC A.G. Ruggiero -- Brookhaven National Laboratory