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Alex Bogacz

Linac and RLAs – Progress on NF-IDS. Alex Bogacz. 0.9 GeV. 244 MeV. 146 m. 79 m. 0.6 GeV/pass. 3.6 GeV. 264 m. 12.6 GeV. 2 GeV/pass. Linac and RLAs - Goals. IDS Goals: Define beamlines /lattices for all components Resolve physical interferences, beamline crossings etc

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Alex Bogacz

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  1. Linac and RLAs – Progress on NF-IDS Alex Bogacz

  2. 0.9 GeV 244 MeV 146 m 79 m 0.6 GeV/pass 3.6 GeV 264 m 12.6 GeV 2 GeV/pass Linac and RLAs - Goals • IDS Goals: • Define beamlines/lattices for all components • Resolve physical interferences, beamline crossings etc • Error sensitivity analysis • End-to-end simulation (machine acceptance) OptiMvs ELEGANT • Component count and costing NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  3. RLA Acceleration - Status • Presently completed lattices • Linear pre-accelerator – solenoid focusing • 4.5 pass Dogbone RLA × 2 (RLA I + RLA II) • Optimized multi-pass linac optics (bisected - quad profile along the linac) • Droplet return arcs (4) matched to the linacs • Transfer lines between the components – injection chicanes • Droplet arcs crossing – Double achromat Optics design • Chromatic corrections with sextupoles at Spr/Rec junctions • Error analysis for the Arc lattices (proof-or-principle) • Magnet misalignment tolerance – DIMAD Monte Carlo Simulation • Focusing errors tolerance – betatron mismatch sensitivity • Piece-wise end-to-end simulation with OptiM (pre-accelerator + RLA I) NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  4. Linear Pre-accelerator – 244 MeV to 909 MeV Transverse acceptance (normalized): (2.5)2eN = 30 mm rad Longitudinal acceptance: (2.5)2 sDpsz/mmc= 150 mm 8 medium cryos 17 MV/m 6 short cryos 15 MV/m 11 long cryos 17 MV/m 2.4 Tesla solenoid 1.4 Tesla solenoid 1.1 Tesla solenoid NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  5. ‘Soft-edge’ Solenoid • Non-zero aperture - correction due to the finite length of the edge : • It introduces axially symmetric edge focusing at each solenoid end: • Hard edge solenoid: NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  6. ‘Soft-edge’ Solenoid – Nonlinear Effects • Nonlinear focusing term DF ~ O(r2) follows from the scalar potential: • Solenoid B-fields • Nonlinear focusing included in particle tracking NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  7. Pre-accelerator Optics – soft vs hard solenoids a = 19.5 cm a = 0 cm NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  8. Linac Optics – OptiM vs ELEGANT a = 19.5 cm a = 19.5 cm Yves Roblin NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  9. Linac Optics – OptiM vs Elegant Transverse acceptance (normalized): (2.5)2eN = 30 mm rad Longitudinal acceptance: (2.5)2 sDpsz/mmc= 150 mm Yves Roblin NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  10. Linac-RLA Acceptance Initial phase-space after the cooling channel at 220 MeV/c bx,y = 2.74 m ax,y = -0.356 bg = 2.08 NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  11. Introduction of synchrotron motion in the linac Longitudinal acceptance: Dp/p=0.17 or Df =93 (200MHz) NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  12. Linear Pre-accelerator – Longitudinal phase-space Transverse acceptance (normalized): (2.5)2eN = 30 mm rad Longitudinal acceptance: (2.5)2 sDpsz/mmc= 150 mm Transport efficiency: 0.996333 NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  13. Longitudinal phase-space tracking OptiM tracking Initial distribution ELEGANT tracking Preliminary Yves Roblin NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  14. Multi-pass Linac Optics – Bisected Linac ‘half pass’ , 900-1200 MeV initial phase adv/cell 90 deg. scaling quads with energy quad gradient 1-pass, 1200-1800 MeV mirror symmetric quads in the linac quad gradient NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  15. Multi-pass linac Optics – bisected linac 2-pass, 1800-2400 MeV minimized beta beating due to under focus 3-pass, 2400-3000 MeV NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  16. m- m- m+ m+ Injection/Extraction Chicane m+ m- NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  17. Re-injection double-chicane 0.9 GeV m+ 1.5 GeV m+ m- m- NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  18. Pre-accelerator–Chicane–Linac Matching a = 2×10-5 NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  19. Pre-accelerator–Chicane–Linac Matching a = 2×10-5 NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  20. Injection-to–Linac – Chromatic Corrections Dfxy = 1800 Dfxy = 1800 Dfxy = 1800 Dfxy = 1800 two families of sextupoles one family of sextupoles uncorrected NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  21. Linac ½-to-Arc1 – Beta Match E =1.2 GeV • Already matched ‘by design’ • 900 phase adv/cell maintained across the ‘junction’ • No chromatic corrections needed NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  22. Linac1-to-Arc2 – Chromatic Compensation E =1.8 GeV • ‘Matching quads’ are invoked • No 900 phase adv/cell maintained across the ‘junction’ • Chromatic corrections needed – two pairs of sextupoles NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  23. Linac1-to-Arc2 - Chromatic Corrections initial uncorrected two families of sextupoles NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  24. Mirror-symmetric ‘Droplet’ Arc – Optics (bout = bin and aout = -ain , matched to the linacs) E =1.2 GeV 2 cells out transition 2 cells out transition 10 cells in NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  25. ‘Droplet’ Arcs scaling – RLA I • Fixed dipole field: Bi =10.5 kGauss • Quadrupole strength scaled with momentum: Gi = × 0.4 kGauss/cm • Arc circumference increases by: (1+1+5) × 6 m = 42 m NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  26. Mirror-symmetric ‘Droplet’ Arc – Optics Arc1 (E =1.2 GeV) 10 cells in 2 cells out 2 cells out Arc2 (E =1.8 GeV) 15 cells in 3 cells out 3 cells out NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  27. Longitudinal Compression in the RLA • Adiabatic compression in the RLA - off-crest acceleration in the linac + non zero momentum compaction in the arcs (M56~6 m) NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  28. ‘Droplet’ Arcs scaling – RLA II • Fixed dipole field: Bi = 40.3 kGauss • Quadrupole strength scaled with momentum: Gi = × 1.5 kGauss/cm • Arc circumference increases by: (1+1+5) × 12 m = 84 m NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  29. RLA II - Linac Optics mirror symmetric quads in the linac 1-pass, 4.6 -6.6 GeV Quad gradient length NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  30. Focusing Error Tolerances – Quadrupole Spec • By design, one can tolerate Arc-to-Arc mismatch at the level of 1% (to be compensated by the dedicated matching quads). • For any given Arc and the following Linac one can evaluate: Fmin ≈1 m and • Thanks to well balanced, tight focusing in the Arcs and compact Spr/Rec optics the last number, 50 m, is factor of 6 smaller than the corresponding quantity for a typical CEBAF Arc-Linac segment. • This yields the required design specification for quadrupoles of 0.2%: NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  31. quadrupole misalignment errors (Gaussian): F:sx = sy= 1 mm sx‘ = sy‘= 0.8 ×10-3 D:sx = sy= 1 mm sx‘ = sy‘= 1.47×10-3 (sx,y' = sx,y/L) Magnet Misalignment Errors • Lattice sensitivity to random misalignment errors via DIMAD Monte-Carlo assuming: Arc 2 RMS Orbit Displacement [m]: X: 0.9486e-02 y: 0.7003e-02 • Orbit drifts at the level of ~3 cm can easily be corrected by pairs of hor/vert correctors (2 kGauss cm ) placed at every quad girder • Similar level of dipole misalignment errors had virtually no effect on random steering NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  32. Summary • Presently completed Lattices: • Pre-accelerator (244 MeV-0.9) + injection double chicane • RLA I (0.9-3.6 GeV) and RLA II (3.6-12.6 GeV) • 4.5 pass linac • Droplet Arcs1-4 • Chromaticity correction with sextupoles validated via tracking • Magnet error lattice sensitivity of Arc lattices • Magnet misalignment error analysis shows quite manageable level of orbit distortion for ~1 mm level of magnet misalignment error. • Great focusing errors tolerance for the presented lattice - 1% of Arc-to-Arc betatron mismatch limit sets the quadrupole field spec at 0.2% NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

  33. Summary – cont. • Piece-wise end-to-end simulation with OptiM/ELEGANT (transport codes) • Solenoid linac • Injection chicane • RLA I • Still to do… • End-to-end simulation with fringe fields (sol. & rf cav.) • Engineer individual active elements (magnets and RF cryo modules) • Element count and costing NFMCC Collaboration Meeting, Oxford, MS, January 14, 2010

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