Andreas Streun Paul Scherrer Institut (PSI) Villigen, Switzerland

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1 Andreas Streun Paul Scherrer Institut (PSI) Villigen, Switzerland Future Research Infrastructures: Challenges and Opportunities Varenna, Italy, July 8-11, 2015

2 Outline Portrait of the SLS; history and achievements The new generation of light sources The challenge to upgrade the SLS A new type of lattice cell for lower emittance: longitudinal gradient bends and anti-bends SLS-2 design: performance, challenges, highlights A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

Paul Scherrer Institut (PSI) 1960 Eidgenössisches Institut für Reaktorforschung (EIR) 1968 Schweizer Institut für Nuklearphysik (SIN) 1988 EIR + SIN = PSI research with photons, neutrons, muons PSI

3 Paul Scherrer Institut (PSI) 1960 Eidgenössisches Institut für Reaktorforschung (EIR) 1968 Schweizer Institut für Nuklearphysik (SIN) 1988 EIR + SIN = PSI research with photons, neutrons, muons PSI Accelerators: 590 MeV proton cyloctron: 1.3 MW beam power spallation neutron source SINQ & muon source SmS 5.8 GeV / 1 Å free electron laser SwissFEL: operation GeV synchrotron light source SLS A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

The SLS 90 kev pulsed (3 Hz) thermionic electron gun transfer lines 100

.10 pm 400±1 ma beam current top-up operation Current vs.

4 The SLS 90 kev pulsed (3 Hz) thermionic electron gun transfer lines 100 MeV pulsed linac Electron beam cross section in comparison to human hair Synchrotron ( booster ) 100 MeV 2.4 [2.7] GeV within 146 ms (~ turns) 2.4 GeV storage ring e x = nm, e y = pm 400±1 ma beam current top-up operation Current vs. time 1 ma shielding walls 4 days A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

5 SLS: beam lines overview A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

2000 First Stored Beam June 2001 Design current 400 ma reached Top up operation started July 2001 First

6 SLS: history 1990 First ideas for a Swiss Light Source 1993 Conceptual Design Report June 1997 Approval by Swiss Government June 1999 Finalization of Building Dec First Stored Beam June 2001 Design current 400 ma reached Top up operation started July 2001 First experiments Jan Laser beam slicing FEMTO May Tesla super bends 2010 ~completion: 18 beamlines A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

7 SLS achievements Rich scientific output > 500 publications in refereed journals/year four spin-off companies (e.g. DECTRIS) Reliability 5000 hrs user beam time per year 97.3% availability ( average) Top-up operation since 2001 constant beam current ma over many days Photon beam stability < 1 mm rms (at frontends) fast orbit feedback system ( < 100 Hz ) undulator feed forward tables, beam based alignment, dynamic girder realignment, photon BPM integration etc... Ultra-low vertical emittance: 0.9 ± 0.4 pm model based and model independent optics correction high resolution beam size monitor developments 150 fs FWHM hard X-ray source FEMTO laser-modulator-radiator insertion and beam line A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

Horizontal emittance normalized to beam energy The storage ring generational change emittance 2 energy circumference 3 Riccardo Bartolini (Oxford University) 4 th low emittance rings workshop,

8 Horizontal emittance normalized to beam energy The storage ring generational change emittance 2 energy circumference 3 Riccardo Bartolini (Oxford University) 4 th low emittance rings workshop, Frascati, Sep , 2014 Storage rings in operation ( ) and planned ( ). The old ( ) and the new ( ) generation. A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

9 New storage rings and upgrade plans Name Energy [GeV] Circumf. [m] Emittance* [pm] Status PETRA-III operational (round beam) MAX-IV SIRIUS ESRF upgrade DIAMOND upgrade started APS upgrade study SPRING 8 upgrade study PEP-X study ALS upgrade study ELETTRA upgrade study SLS now ** operational SLS (?) ? 2024? *Emittance without with damping wigglers **without FEMTO insertion A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

10 The Multi-Bend Achromat (MBA) Miniaturization small vacuum chambers [NEG coated] high magnet gradients more cells in given circumference A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

11 SLS upgrade constraints and challenges Constraints get factor lower emittance ( pm) keep circumference & footprint: hall & tunnel. re-use injector: booster & linac. keep beam lines: avoid shift of source points. dark period for upgrade months Main challenge: small circumference (288 m) Multi bend achromat: e (number of bends) 3 ring ring + DW Damping wigglers (DW): e radiated power Low emittance from MBA and/or DW requires space! Scaling MAX IV to SLS size and energy gives e 1 nm New lattice concept e pm A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

12 Theoretical minium emittance (TME) cell dilemma Betafunctions [m] Dispersion [m] Conditions for minimum emittance (h = 1/r = eb/p curvature) b L = ho 2 15 min min o = 2 hl 24 periodic/symmetric cell: b = h = 0 at ends over-focusing of b x phase advance m min = nd focus, useless overstrained optics, huge chromaticity... long cell better have two relaxed cells of f/2 MBA concept... o 3 min ( f[ ]) xo [pm rad] ( E[GeV]) J x e = b x b y h f, L, h A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

Conventional cells = relaxed TME cells F = Deviations from TME conditions e e xo min xo b = b b o min o Ellipse equations for emittance o min o Cell phase advance m 6 b tan

13 Conventional cells = relaxed TME cells F = Deviations from TME conditions e e xo min xo b = b b o min o Ellipse equations for emittance o min o Cell phase advance m 6 b tan = 2 15 ( d 3) d h = h ( d 1) ( b F) = F 1 4 Real cells: m < 180 F ~ MBA: F > 10 A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

14 how to do better? 1. disentangle dispersion h and beta function b x release constraint: focusing is done with quads only. use anti-bend (AB) out of phase with main bend suppress dispersion (h o 0) in main bend center. allow modest b xo for low cell phase advance. 2. optimize bending field for minimum emittance release constraint: bend field is homogeneous. use longitudinal gradient bend (LGB) highest field at bend center (h o = (e/p) B o ) reduce field h(s) as dispersion h(s) grows sub-tme cell (F < 1) at moderate phase advance A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

15 step 1: the anti-bend (AB) General problem of dispersion matching: dispersion is a horizontal trajectory dispersion production in dipoles defocusing : h > 0 Quadrupoles in conventional cell: over-focusing of beta function b x insufficient focusing of dispersion h dispersion: anti-bend off / on disentangle h and b x use negative dipole: anti-bend kick Dh =, angle < 0 out of phase with main dipole b x b y negligible effect on b x, b y relaxed TME cell, 5, 2.4 GeV, J x 2 Emittance: 500 pm / 200 pm A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

I 4 2 = I bh( b 2k) ds I2 J x = 1 I AB emittance contribution AB emittance effects 2 3 AB 3 h e I5 = h H ds h L L b h is large and constant at AB low field, long magnet Cell emittance (2 AB +main

16 I 4 2 = I bh( b 2k) ds I2 J x = 1 I AB emittance contribution AB emittance effects 2 3 AB 3 h e I5 = h H ds h L L b h is large and constant at AB low field, long magnet Cell emittance (2 AB +main bend) main bend angle to be increased by 2 in total, still lower emittance AB as combined function magnet Increase of damping partition J x vertical focusing in normal bend horizontal focusing in anti-bend. horizontal focusing required anyway at AB AB = off-centered quadrupole half quadrupole 4 2 b x b y Disp. h 2 A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

I 4 2 = I bh( b 2k) ds I2 J x = 1 I AB impact on chromaticity 4 2 2 Anti-bend negative momentum compaction a small large 1 a = hh ds hh ds C LGB AB negative < 0 Head-tail stability for negative

17 I 4 2 = I bh( b 2k) ds I2 J x = 1 I AB impact on chromaticity Anti-bend negative momentum compaction a small large 1 a = hh ds hh ds C LGB AB negative < 0 Head-tail stability for negative chromaticity! side note: AB history 1980 s/90 s: proposed for isochronous rings and to increase damping - but PAC 1989 A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

18 step 2: the longitudinal gradient bend (LGB) e = 3 I 5 h( s) H ( s) ds L Dispersion s betatron amplitude H = Orbit curvature h(s) = B(s)/(p/e) ( ah bh') b Longitudinal field variation h(s) to compensate H (s) variation Beam dynamics in bending magnet A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10, h Curvature is source of dispersion: h' '( s) = h( s) h'( s) h( s) Horizontal optics ~ like drift space: b 1 a 0 2 ( s) = b 2a 0s b s 0 0 Assumptions: no transverse gradient (k = 0); rectangular geometry Variational problem: find extremal of h(s) for I = ( h h h h h h h numerical optimization 3 5 f s,, ', '') ds min with functional f = H ( s,, ', '') '' L 2 2

19 LGB numerical optimization Half bend in N slices: curvature h i, length Ds i Knobs for minimizer: {h i }, b 0, h 0 Objective: I 5 Constraints: length: SDs i = L/2 angle: Sh i Ds i = F/2 [ field: h i < h max ] [ optics: b 0, h 0 ] Results: hyperbolic field variation (for symmetric bend, dispersion suppressor bend is different) Trend: h 0, b 0 0, h 0 0 I Results for half symmetric bend ( L = 0.8 m, F = 8, 2.4 GeV ) optimized hyperbola fit homogeneous I 5 contributions A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

20 LGB optimization with optics constraints Numerical optimization of field profile for fixed b 0, h 0 Emittance (F) vs. b 0, h 0 normalized to data for TME of hom. bend F = 1 F 0.3 F = 1 small (~0) dispersion at centre required, but tolerant to large beta function A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

21 The LGB/AB cell Conventional cell vs. longitudinal-gradient bend/anti-bend cell both: angle 6.7, E = 2.4 GeV, L = 2.36 m, Dm x = 160, Dm y = 90, J x 1 conventional: e = 990 pm (F = 3.4) LGB/AB: e = 200 pm (F = 0.69) Disp. h Disp. h b x b y b x b y dipole field quad field total field } at R = 13 mm longitudinal gradient bend anti-bend A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

22 SLS-2 lattice layout TBA 7BA lattice: ½ ½ cells of LGB/AB type periodicy 3: 12 arcs and 3 different straight types: 6 4 m m 3 7 m m split long straights: m m beam pipe: 64 mm x 32 mm 20 mm magnet aperture 26 mm A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

Superbends in arcs 2/6/10 3 2.9 T 3 5.0 T A.

23 SLS-2 lattice db02l (one superperiod = 1/3 of ring) optics and magnetic field (field at poletips for R = 13 mm) Superbends in arcs 2/6/ T T A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

24 SLS-2 lattice parameters Name SLS* ) db02l fa01f status operating baseline fallback Emittance at 2.4 GeV [pm] Lattice type TBA 7BA 5BA Total absolute bending angle Working point Q x/y / / / Natural chromaticities C x/y 67.0 / / / 39.9 Optics strain 1) Momentum compaction factor [10 4 ] Dynamic acceptance [mm.mrad] 2) Radiated Power [kw] 3) rms energy spread [10 3 ] damping times x/y/e [ms] 9.0 / 9.0 / / 8.0 / / 6.8 / 4.1 1) product of horiz. and vert. normalized chromaticities C/Q 2) max. horizontal betatron amplitude at stability limit for ideal lattice 3) assuming 400 ma stored current, bare lattice without IDs *) SLS lattice d2r55, before FEMTO installation (<2005) A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

Non-linear optimization 13 sextupole & 10 octupole families step 1: perturbation theory: insufficient 1 st & 2 nd

optimizer objectives: dynamic aperture at Dp/p = 0, 3% contraints: tune fooprint within ½ integer box Lattice

from existing booster synchrotron Touschek lifetime 3.2 hrs 1 ma/bunch, 10 pm vertical emittance, 1.

25 Non-linear optimization 13 sextupole & 10 octupole families step 1: perturbation theory: insufficient 1 st & 2 nd order sextupole terms 1 st order octupole terms up to 3 rd order chromaticities step 2: multi-objective genetic optimizer objectives: dynamic aperture at Dp/p = 0, 3% contraints: tune fooprint within ½ integer box Lattice acceptance results (ideal lattice) horizontal acceptance 10 mm mrad sufficient for off-axis multipole injection from existing booster synchrotron Touschek lifetime 3.2 hrs 1 ma/bunch, 10 pm vertical emittance, 1.43 MV overvoltage further increase to 7-9 hrs by harmonic RF system. A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

26 More challenges... work just started Collective effects large resistive wall impedance ( aperture 3 ) low momentum compaction factor a, and a < 0 close thresholds for turbulent bunch lengthening head-tail stability for chromaticity 0 intrabeam scattering 15-30% emittance increase Alignment tolerances common magnet yoke = girder initial mechanical alignment will be insufficient extensive use of beam based alignment methods longer commissioning than 3 rd gen. light source A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

planes SLS SLS-2 SLS-2 RB A new on-axis injection scheme cope with reduced aperture (physical or dynamic) interplay of radiation damping and

27 Advanced options Figure taken from R. Hettel, JSR 21 (2014) p.843 Round beam scheme Wish from users (round samples...) Maximum brightness & coherence Mitigation of intrabeam scattering blow-up Möbius accelerator : beam rotation on each turn to exchange transverse planes SLS SLS-2 SLS-2 RB A new on-axis injection scheme cope with reduced aperture (physical or dynamic) interplay of radiation damping and synchrotron oscillation forms attractive channel in longitudinal phase space for off-energy off-phase on-axis injection. A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

28 Photon energy range Longitudinal gradient superbend Dipole Flux [ph/mr^2/sec/0.1%bw] 5.00E E E E E E T 2.95 T 5.7 T YBCO 1) HTS 2) tape in canted-cos-theta configuration on hyperbolic mandrel hyperbolic field profile open for radiation fan > 5T peak field Courtesy Ciro Calzolaio, PSI 1) Yttrium-Barium-Copper-Oxide 2) High Temperature Superconductor A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

29 Time schedule Jan Letter of Intent submitted to SERI (SERI = State secretariat for Education, Research and Innovation) schedule and budget studies & prototypes 2 MCHF new storage ring 63 MCHF beamline upgrades 20 MCHF Oct positive evaluation by SERI: SLS-2 is on the roadmap. Concept decisions fall Conceptual design report end A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

30 Summary The Swiss Light Source is successfully in operation since 15 years......but progress in storage ring design enforces an upgrade. Upgrade of the Swiss Light Source SLS has to cope with a rather compact lattice footprint but the new LGB/AB cell provides five times lower emittance than a conventional lattice cell: Anti bends (AB) disentangle horizontal beta and dispersion functions. Longitudinal gradient bends (LGB) provide minimum emittance by adjusting the field to the dispersion. The baseline design for SLS-2 is a 12 7BA lattice providing times lower emittance. The design is challenged by non-linear optics optimization, beam instabilities and correction of lattice imperfections. A conceptual design report is scheduled for end A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

31 Acknowledgements Beam Dynamics: Michael Ehrlichman, Ángela Saá Hernández, Masamitsu Aiba, Michael Böge Instabilities and impedances: Haisheng Xu, Eirini Koukovini-Platia (CERN), Lukas Stingelin, Micha Dehler, Paolo Craievich Magnets: Ciro Calzolaio, Stephane Sanphilippo, Vjeran Vrankovic, Alexander Anghel Vacuum system: Andreas Müller, Lothar Schulz General concept and project organisation: Albin Wrulich, Lenny Rivkin, Terry Garvey, Uwe Barth A. Streun, PSI Swiss Light Source: the next 20 years, Varenna, July 10,

SLS Status and Development of an SLS2 Upgrade

SLS Status and Development of an SLS2 Upgrade Michael Ehrlichman, Masamitsu Aiba, Michael Böge, Angela Saa-Hernandez, Andreas Streun Paul Scherrer Institut, Villigen, Switzerland ESLS XXII meeting, Grenoble,