Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Alex Bogacz Pros and Cons of the Acceleration Scheme Benefits Challenges

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Acceleration Scenario – IDS Baseline Linear Pre-accelerator (244 MeV to 900 MeV) RLA I  4.5 pass, 0.6 GeV/pass, (0.9 GeV to 3.6 GeV ) RLA II  4.5 pass, 2 GeV/pass (3.6 GeV to 12.6 GeV ) Non scaling FFAG (12.6 GeV to 25 GeV )

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, GeV/pass 3.6 GeV 0.9 GeV 244 MeV 146 m 79 m 2 GeV/pass 264 m 12.6 GeV Towards Engineering Design Foundation

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Benefits/Pros. Large Acceptance Transverse (norm): 30 mm rad Longitudinal (norm): 150 mm momentum spread:   p/p = 0.07 bunch length:  z = 176 mm Synchrotron oscillations induced  full synchrotron period along the linac Correction of energy gain across the bunch (initial bunch-length: 89 0 rf) Significant longitudinal compression   p/p : 0.07  0.03 Challenges/Cons. Reduced effective acceleration grad. (825MeV RF vs 665MeV energy gain) One 1-cell cavity cryo-moduls in front Far off-crest acceleration; initially 74 0 Three different styles of cryo-modules Magnetic shielding of the SRF cavities Individual rf phase control for each cavity Linear Pre-accelerator (244 MeV MeV)

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Linear Pre-accelerator – 244 MeV to 909 MeV 6 short cryos 15 MV/m 8 medium cryos 17 MV/m 11 long cryos 17 MV/m 1.1 Tesla solenoid 1.4 Tesla solenoid 2.4 Tesla solenoid

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Linear Pre-accelerator – 244 MeV to 909 MeV Transverse acceptance (normalized): (2.5) 2   = 30 mm rad Longitudinal acceptance: (2.5) 2   p  z /m  c  = 150 mm

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Two-step ‘Dogbone’ RLAs (0.9  3.6  12.6 GeV) Benefits/Pros. Effective usage of high gradient SRF RLA I: 4.5 pass through 0.6 GeV linac RLA II: 4.5 pass through 2 GeV linac Individual return Arcs for each pass Path-length adjustment after each pass through the linac Further longitudinal rf compression Adjustable gang phase for each pass Nonzero momentum compaction in the Arcs (M 56 = 5 m) Uniform periodicity FODO based optics Relatively low quadrupole gradients Modest chromatic corrections required Two pairs of sextupoles in Spreader and Recombiner regions Challenges/Cons. Large total length of the Arcs RLA I: =772 m RLA II: =1544 m Multiple (3) injection double chicanes Spreader/Recombiner switchyards required at both linac ends Multiple ‘crossings’ of the droplet Arcs (4 crossings in each RLA)

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Injection/Extraction double-chicane      

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Mirror-symmetric ‘Droplet’ Arc – Optics 10 cells in 2 cells out (  out =  in and  out = -  in, matched to the linacs) Arc dipoles $Lb=100 cm $B=10.5 kG Arc quadrupoles $Lb=50 cm $G= 0.4 kG/cm transition phase adv./cell  x,y = 90 0 E =1.2 GeV

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 ‘Droplet’ Arcs scaling – RLA I i = 1…4E i [GeV]p i /p 1 cell_outcell_inlength [m] Arc ×22× Arc21.83/2 2×32× Arc ×42× Arc43.05/22×52× Fixed dipole field: B i =10.5 kGauss Quadrupole strength scaled with momentum: G i = × 0.4 kGauss/cm Arc circumference increases by: (1+1+5) × 6 m = 42 m

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Linac ½-to-Arc1 – Beta Match E =1.2 GeV Already matched ‘by design’ 90 0 phase adv/cell maintained across the ‘junction’ No chromatic corrections needed

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Linac1-to-Arc2 – Beta Match E =1.8 GeV Noticeable mis-match at the end of Linac1 ‘Matching quads’ are invoked

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Linac1-to-Arc2 – Beta Match E =1.8 GeV No 90 0 phase adv/cell maintained across the ‘junction’ Chromatic corrections needed

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Linac1-to-Arc2 – Chromatic compensation E =1.8 GeV Chromatic corrections with two pairs of sextupoles

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Linac1-to-Arc2 - Chromatic Corrections initial uncorrected two families of sextupoles

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 ‘Droplet’ Arcs scaling – RLA II i = 1…4E i [GeV]p i /p 1 cell_outcell_inlength [m] Arc ×22× Arc26.63/2 2×32× Arc ×42× Arc410.65/22×52× Fixed dipole field: B i = 40.3 kGauss Quadrupole strength scaled with momentum: G i = × 1.5 kGauss/cm Arc circumference increases by: (1+1+5) × 12 m = 84 m

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Arcs ‘Crossing’ - Vertical Bypass  

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Non-Scaling FFAG Ring ( GeV) Benefits/Pros. Large chromatic acceptance (2 × inj. energy) Large number of passes through RF cavities At least 8, could be made as high as 15 RF systems expensive (cost benefit - RLA limited to 4-5 passes due to switchyard complexity) Acceleration using high-gradient SRF Compact ring: 463 m circumference Challenges/Cons. Injection and extraction kickers Relatively strong fields (a few kGauss) Large aperture (11 cm wide if open mid-plane, >20 cm wide if a ‘closed box’, what is are the limits ??) Moderately fast (10 -6 sec.) More efficient designs introduce stronger longitudinal distortions No synchrotron oscillations No correction of energy loss down the bunch train Small, probably tolerable effect Correctable with slight frequency offset No correction of time of flight dependence on transverse amplitude

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Injection and extraction kickers Scott Berg

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Time of flight dependence on transverse amplitude High transverse amplitude particles get out of synch with RF Synchrotron oscillations don't completely correct the problem - they turn an ever- increasing time offset into a relatively constant (and modest) energy offset Different phase space channels seen by different amplitudes: black - low amplitude, grey - high amplitude. Scott Berg

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008  Limits ring acceptance and ability to stage rings  High transverse amplitude particles get out of synch with RF  Possible solutions under investigation: reduce tune range during acceleration use higher average accelerating gradient (presently implemented for the IDS) add higher RF harmonics add some chromaticity corrections high amplitude low amplitude S. Machida TOF dependence on transverse amplitude

Operated by JSA for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Alex Bogacz NuFact’08, Valencia, Spain, July 4, 2008 Summary Acceleration Goals – Large acceptance acceleration to 25 GeV and beam ‘shaping’ Various fixed field accelerators at different stages Alternating solenoid SRF Linac Two SRF RLA’s Non-scaling FFAG IDS Acceleration scenario optimized to take maximum advantage of appropriate acceleration scheme at a given stage Laying out engineering design foundation Define beamlines/lattices for all components Design lattices for transfer lines between the components Resolve physical interferences, beamline crossings etc  Floor Coordinates Carry out end-to-end tracking study  Machine Acceptance