La#ce Design for the MAX IV 3 GeV Storage Ring A Mul<bend Achromat with Higher- order Mul<poles
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, 2012 2/25
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 ( 1 2 +2b 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
Mul;bend Achromats Concept already published in the 1990s NIM- A 335 1993, 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
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
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
MAX IV Mul;bend Achromat La^ce y [m] 2.0 5 10 15 20 25 x [m] Aqer several itera;ons (~2003-2011) arrived at 20- fold 7BA @ 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, 120701 (2009) IPAC 11, THPC059, p.3029 ver;cal emibance adjusted to diffrac;on limit (~1 Å) 7/25
MAX IV Mul;bend Achromat La^ce y [m] 2.0 5 10 15 20 25 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
MAX IV Mul;bend Achromat La^ce y [m] 2.0 5 10 15 20 25 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
MAX IV Mul;bend Achromat La^ce y [m] 2.0 5 10 15 20 25 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
MAX IV Mul;bend Achromat La^ce y [m] 2.0 Insertion Device Matching Cell Matching Cell 5 10 15 20 25 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.1262 11/25
MAX IV MBA Op;cs 18 16 β x β y η x 0.08 0.07 ν x = 42.20 ν y = 16.28 14 0.06 Beta Functions [m] 12 10 8 6 0.05 0.04 0.03 0.02 Dispersion [m] βx * = 9 m βy * = 2 m ηx * = 8 cm 4 0.01 σx * = 42-60 µm 2 0 0 0 5 10 15 20 25-0.01 σy * = 2-5 µm s [m] 12/25
MAX IV MBA Op;cs 18 16 β x β y η x 0.08 0.07 Dipoles ~0.5 T 14 0.06 ~9 T/m Beta Functions [m] 12 10 8 6 4 0.05 0.04 0.03 0.02 0.01 Dispersion [m] Quadrupoles ~40 T/m Sextupoles ~2000 T/m 2 2 0 0 5 10 15 20 25 0-0.01 Octupoles ~30000 T/m 3 s [m] 13/25
Nonlinear Op;cs 18 16 β x β y η x 0.08 0.07 ξ x = - 50.0 ξ y = - 50.2 14 0.06 Beta Functions [m] 12 10 8 6 0.05 0.04 0.03 0.02 Dispersion [m] Cell phase advance: 2π (2;3/4) 4 0.01 2 0 0 0 5 10 15 20 25 s [m] -0.01 14/25
Nonlinear Op;cs y [m] 2.0 5 10 15 20 25 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
Nonlinear Op;cs y [m] 2.0 5 10 15 20 25 x [m] Dispersion- free octupoles PRST- AB 14, 030701 (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
Nonlinear Op;cs y [m] 2.0 5 10 15 20 25 x [m] Op;miza;on objec;ves: PRST- AB 14, 030701 (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
Nonlinear Op;cs 2.0 y [m] 7 6 5 Dynamic Aperture, δ=0.0% Dynamic Aperture, δ=4.5% Dynamic Aperture, δ=-4.5% Vacuum Chamber Physical Aperture Required Aperture y [mm] 5 10 15 20 25 4 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 0-15 -10-5 0 5 10 15 wrap up chroma;c tune shiq around WP x [mm] PRST- AB 14, 030701 (2011) minimize tune footprint large DA on&off mom. 18/25
Nonlinear Op;cs DA is stable under influence of IDs & errors y [mm] 7 6 5 4 3 2 1 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 0-15 -10-5 0 5 10 15 x [mm] Mul;pole Errors: Upright and skew mul;poles added 19/25
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
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
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
Extra Ingredients: Making the MBA La^ce Work 500 ma in 176 bunches @ ~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
Extra Ingredients: Making the MBA La^ce Work 500 ma in 176 bunches @ ~300 pm rad, narrow Cu chamber worry about Touschek life;me, instabili;es, collec;ve effects, IBS,... Touschek [h] 55 50 45 40 very long bunches thanks to 35 100 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 29 28 + x adding IDs (DWs?) reduce emibance increase τ 0.32 0.36 + 0 0.5 1 1.5 2 2.5 3 x [nm rad] 24/25
Extra Ingredients: Making the MBA La^ce Work 500 ma in 176 bunches @ ~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 IBS @ 500 ma reduced from ~42% to ~11% with Landau cavi;es PRST- AB 12, 120701 (2009) 25/25