La#ce Design for the MAX IV 3 GeV Storage Ring. A Mul<bend Achromat with Higher- order Mul<poles

Transcription

1 La#ce Design for the MAX IV 3 GeV Storage Ring A Mul<bend Achromat with Higher- order Mul<poles

2 MAX IV Facility at a Glance MAX IV design premise: one size does not fit all Short pulses: 3.5 GeV linac & SPF (~30 fs, 100 Hz), FEL upgrade op;on High average brightness: 1.5 GeV storage ring DBA la^ce, 6 nm rad, IR & UV users 3 GeV storage ring MBA la^ce, ~300 pm rad, x- ray users Sep 10, 2012 Simon C. Leemann Workshop on Accelerator R&D for Ul;mate Storage Rings, Huairou, Beijing, China, Oct 30 - Nov 1, /25

3 Mul;bend Achromats Equilibrium emibance in a flat ring " 0 [nm rad] = 1470 E[GeV] 2 I 5, J x =1 J x I 2 I 2 = I ds 2, I 4 = I ( b 2)ds, I 5 = I H 3 ds I 4 I 2 H = x 2 +2 x 0 + x 02 TME: minimize I 5 /I 2 overstrained op;cs? MBA: many weak dipoles relax op;cs! " 0 [nm rad] = 7.8 J x E[GeV] 2 [ ] 3 F ( x, ) 12 p 15, [ ]3 / 1 N 3 bend 3/25

4 Mul;bend Achromats Concept already published in the 1990s NIM- A , Einfeld et al.: A modified QBA op/cs for low emi5ance rings EPAC 94, Joho et al.: Design of a Swiss Light Source PAC 95, Einfeld et al.: Design of a Diffrac/on Limited Light Source QBA 6x7BA 12x7BA PAC 95: Kaltchev et al.: La>ce Studies for a High- brightness Light Source QBA, 5BA, 6BA 4/25

5 Mul;bend Achromats Issues: space requirements, no. of user straights weak bends large circumference cost! need very compact op;cs strong focusing & weak bends low dispersion strong chroma;c sextupoles need to carefully op;mize nonlinear op;cs 5/25

6 Mul;bend Achromats Issues: space requirements, no. of user straights weak bends large circumference cost! need very compact op;cs strong focusing & weak bends low dispersion strong chroma;c sextupoles need to carefully op;mize nonlinear op;cs Early 2000s: MAX- lab convinced innova;ve technology allows for very compact op;cs MBA is robust & inexpensive path to very low emibance 6/25

7 MAX IV Mul;bend Achromat La^ce y [m] x [m] Aqer several itera;ons (~ ) arrived at 20- fold 3 GeV, 528 m circumference 19 user straights (4.6 m) 40 short straights (1.3 m, RF & diagnos;cs) 326 pm rad bare la^ce emibance NIM- A 508, 480 (2003) PAC 07, MOZAAB02, p.74 NIM- A 587, 221 (2008) PRST- AB 12, (2009) IPAC 11, THPC059, p.3029 ver;cal emibance adjusted to diffrac;on limit (~1 Å) 7/25

8 MAX IV Mul;bend Achromat La^ce y [m] x [m] 7BA: 5 unit cells (3 o ), 2 matching cells (1.5 o ) Compact op;cs combined- func;on magnets gradient dipoles (increases J x reduces ε 0 ) quadrupole- sextupole sandwich sextupole- dipole sandwich } instead of originally foreseen combined- func;on magnets tuning flexibility, beber DA 8/25

9 MAX IV Mul;bend Achromat La^ce y [m] x [m] Many distributed sextupoles correct chroma;city where it s created (limits chroma;c beta bea;ng) Dedicated octupoles nonlinear op;miza;on 9/25

10 MAX IV Mul;bend Achromat La^ce y [m] x [m] Extra windings on all sextupoles and octupoles skew quads betatron coupling, ver;cal dispersion adjust ver;cal beam size in IDs to diffrac;on limit auxiliary sextupoles (outside of families!) nonlinear op;cs correc;ons 10/25

11 MAX IV Mul;bend Achromat La^ce y [m] 2.0 Insertion Device Matching Cell Matching Cell x [m] Tuning & ID matching: quadrupole doublets in each matching cell pole- face strips in dipoles ideally ID gap movement should be transparent to rest of machine (linear and nonlinear op;cs!) PAC 11, TUP235, p /25

12 MAX IV MBA Op;cs β x β y η x ν x = ν y = Beta Functions [m] Dispersion [m] βx * = 9 m βy * = 2 m ηx * = 8 cm σx * = µm σy * = 2-5 µm s [m] 12/25

13 MAX IV MBA Op;cs β x β y η x Dipoles ~0.5 T ~9 T/m Beta Functions [m] Dispersion [m] Quadrupoles ~40 T/m Sextupoles ~2000 T/m Octupoles ~30000 T/m 3 s [m] 13/25

14 Nonlinear Op;cs β x β y η x ξ x = ξ y = Beta Functions [m] Dispersion [m] Cell phase advance: 2π (2;3/4) s [m] /25

15 Nonlinear Op;cs y [m] x [m] Large natural chroma;city Correct with strong chroma;c sextupoles (low dispersion) Adjust sextupoles correc;on (5 families) to minimize RDTs (SVD & weigh;ng, OPA, Tracy- 3) But... strong sextupoles give rise to large ADTS 15/25

16 Nonlinear Op;cs y [m] x [m] Dispersion- free octupoles PRST- AB 14, (2011) correct ADTS to first order (instead of 2nd- order correc;on with sextupoles and possible run- away issues) Efficient use of octupoles for ADTS correc;on frees up sextupoles for chroma;c correc;ons while minimizing 1st- order RDTs 16/25

17 Nonlinear Op;cs y [m] x [m] Op;miza;on objec;ves: PRST- AB 14, (2011) set 1st- order ADTS terms to minimize overall ADTS over as much of physical acceptance as possible adjust higher- order chroma;ci;es ( decapoles?) to wrap up chroma;c tune shiq around WP minimize tune footprint large DA on&off mom. 17/25

18 Nonlinear Op;cs 2.0 y [m] Dynamic Aperture, δ=0.0% Dynamic Aperture, δ=4.5% Dynamic Aperture, δ=-4.5% Vacuum Chamber Physical Aperture Required Aperture y [mm] x [m] Op;miza;on objec;ves: 3 set 1st- order 2 ADTS terms to minimize overall ADTS over as much of physical acceptance as possible 1 adjust higher- order chroma;ci;es ( decapoles?) to wrap up chroma;c tune shiq around WP x [mm] PRST- AB 14, (2011) minimize tune footprint large DA on&off mom. 18/25

19 Nonlinear Op;cs DA is stable under influence of IDs & errors y [mm] Ideal machine with 10 pmul, δ=0.0% Machine with errors, δ=0.0% Vacuum Chamber Physical Aperture Required Aperture IVU pmul : 3.7 m long, 1.1 T peak field, 18.5 mm period, 4.2 mm gap Misalignments: 50 µm rms H/V 0.2 mrad rms roll 25 µm rms H/V 0.2 mrad rms roll Field Errors: 0.05% rms within each family } for } for each magnet block all magnets within x [mm] Mul;pole Errors: Upright and skew mul;poles added 19/25

20 Extra Ingredients: Making the MBA La^ce Work Small magnet bores (~25 mm) in order to achieve required gradients compact op;cs but this limits vacuum aperture doesn t lead to MA problems because of low dispersion but pumping cross- sec;on limited & insufficient space for pumps, absorbers, antechambers, etc. 20/25

21 Extra Ingredients: Making the MBA La^ce Work Small magnet bores (~25 mm) in order to achieve required gradients compact op;cs but this limits vacuum aperture doesn t lead to MA problems because of low dispersion but pumping cross- sec;on limited & insufficient space for pumps, absorbers, antechambers, etc. Instead, linear pumping through slim NEG- coated Cu chamber with external cooling channel Eshraq Al- Dmour s presenta;on 21/25

22 Extra Ingredients: Making the MBA La^ce Work Many small magnets machined from a common solid iron block installed on massive concrete supports alignment & stability Mar;n Johansson s presenta;on Magnet Block Concrete Support 22/25

23 Extra Ingredients: Making the MBA La^ce Work 500 ma in 176 ~300 pm rad, narrow Cu chamber worry about Touschek life;me, instabili;es, collec;ve effects, IBS,... very long bunches thanks to 100 MHz main RF system Mikael Eriksson s presenta;on Landau cavi;es at the third harmonic stretch bunches by up to a factor 5 increases Touschek life;me 23/25

24 Extra Ingredients: Making the MBA La^ce Work 500 ma in 176 ~300 pm rad, narrow Cu chamber worry about Touschek life;me, instabili;es, collec;ve effects, IBS,... Touschek [h] very long bunches thanks to MHz main RF system Mikael Eriksson s presenta;on 30 low ε + large MA good Touschek life;me 4/10/LC 4/0/LC 28.5 Landau cavi;es at the bare/lc third harmonic stretch bunches by up to a factor 25 5 increases Touschek life;me x adding IDs (DWs?) reduce emibance increase τ x [nm rad] 24/25

25 Extra Ingredients: Making the MBA La^ce Work 500 ma in 176 ~300 pm rad, narrow Cu chamber worry about Touschek life;me, instabili;es, collec;ve effects, IBS,... very long bunches thanks to 100 MHz main RF system Mikael Eriksson s presenta;on Landau cavi;es at the third harmonic stretch bunches by up to a factor 5 increases Touschek life;me bunch lengthening also enables us to cope with strong IBS: emibance blowup due to 500 ma reduced from ~42% to ~11% with Landau cavi;es PRST- AB 12, (2009) 25/25