WIR SCHAFFEN WISSEN HEUTE FR MORGEN Andreas Streun

WIR SCHAFFEN WISSEN – HEUTE FÜR MORGEN Andreas Streun : : Paul Scherrer Institut SLS 2. 0 machine Beamline Proposal Workshop, October 23 -24 , 2018, PSI

Outline 1. Project Status 2. How we upgrade SLS to a light source which is competitive > 2025 3. Why we need to modify the ring tunnel 4. Beam parameters and source properties A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 2/25

1. Project Status Funding procedure w Jan. 2014: letter of intent submitted to SERI w Jan. 2018: submission of proposal to SNF w Sep. 2018: ETH Board gives highest rating (A) for SLS 2. 0 proposal § Sep. 10 accelerator & science, Sep. 26/27 implementation & governance w Dec. 12/13. 2018: ETH board decision on inclusion in “roadmap” implementation in SERI message 2021 -24 Time schedule and resources w 2023 -24 “dark period” counting backwards procurement of magnets mid 2019, vacuum components < mid 2020 w 2018 -20: 78 FTE & 14 MCHF “pre-financing” w 2021 -24: 279 FTE & 90 MCHF “project” SLS renewal program: modifications which would be needed to keep SLS operational even in the event of no up-grade (maintenance, e. g. new BPM system ) w 2018 -24: 205 FTE & 25 MCHF “renewal” w groups getting engaged but conflicting activities (Swiss. FEL, ATHOS, HIPA, external) w resource loaded planning in progress A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 3/25

Accelerator Design w Start of new storage ring design 2012, objectives: § § > 30 x smaller emittance re-use of injector complex and building w Conceptual design completed in 2017 SLS-2 conceptual design report, Dec. 21, 2017 www. lib 4 ri. ch/archive/nebis/PSI_Berichte_000478272/PSI-Bericht_17 -03. pdf attachment to SNF application Jan. 2018 summary publication in Journal of Synchrotron Radiation SLS-2 – the upgrade of the Swiss Light Source , JSR 25, 631 (2018) https: //doi. org/10. 1107/S 1600577518002722 w Lattice “freeze” Sep. 2018 SLS 2. 0 baseline lattice, Tech. note SLS 2 -SA 81 -004 http: //ados. web. psi. ch/SLS 2/Notes/SLS 2 -SA 84 -002_sls 2 notes. pdf base for technical design A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 4/25

SLS 2. 0 features and challenges Basic features w 100 pm emittance (50 lower than SLS now) w 12 -fold lattice symmetry local tunnel modifications w magnet technology: permanent and superconducting w vacuum technology: NEG coating (Ti-V-Zr getter) w re-use of injector complex (booster and linac) Critical issues w High field permanent magnet design w Confidence in stability w. r. t. impedance w Acquisition of sufficient manpower in GFA and LOG w Acquisition of 4000 m 2 space for storage w limit shutdown (dark period) to max. 18 month A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 5/25

2. Compact low emittance lattice Light source figure of merit: horizontal emittance ex § § determines brightness, coherent fraction etc. vertical emittance is small (in a flat storage ring) SLS emittances ex = 5500 pm. rad, ey = 5. . . 10 pm. rad Upgrade design objective: factor > 30 lower emittance ex Approximate emittance scaling: ex (Energy)2 / (Circumference)3 Scaling of new ring designs to SLS: handikap: small circumference SLS E = 2. 4 Ge. V MAX IV E = 3. 0 Ge. V SIRIUS E = 3. 0 Ge. V ESRF-EBS E = 6. 0 Ge. V SLS 2. 0 C = 288 m C = 528 m C = 518 m C = 844 m ex = 328 pm ex = 240 pm ex = 147 pm 1290 pm 950 pm 590 pm E = 2. 4 Ge. V C = 290. 4 m ex = 99 pm ( 125 pm at 400 m. A) Novel design from first principles A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 6/25

Emittance suppression Quantum excitation = source of emittance keep off-momentum orbit close to reference orbit d =Dp/p minimize dispersion at locations of radiation (i. e. at bending magnets) focusing in bending magnets many small bends to limit dispersion growth multi-bend achromat still insufficient in our case. . . A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 7/25

The novel LGB-RB lattice cell Standard cell w quadrupoles to focus dispersion w dispersion at center > 0 LGB-RB cell orbit for Dp < 0 Step 1: decouple dispersion from horizontal focusing ! w displaced quadrupoles = reverse bending magnets (RB) dispersion at centre 0 Step 2: exploit small dispersion at centre ! w longitudinal field variation in dipole magnet: = longitudinal gradient bend (LGB) factor 4. . 5 lower emittance B(s) s A. Wrulich & AS, Compact low emittance light sources based on longitudinal gradient bending magnets, NIM A 770 (2015) 98– 112 AS, The anti-bend cell for ultralow emittance storage ring lattices, NIM A 737 (2014) 148– 154 B. Riemann & AS, Low emittance lattice design from firrst principles: reverse bending and longitudinal gradient bends, to be submitted A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 8/25

SLS 2. 0 and the new light sources generation Emittance normalized to energy vs. circumference ex (Energy)2 / (Circumference)3 “Bartolini plot” Theoretical Emittance scaling e 2 C -3 SLS K 2 -1 improvement 20 operational SLS 2. 0 commissioning or construction planned with damping wigglers A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 upgrade projects 9/25

SLS and SLS 2. 0 arcs SLS arc (from long to short straight) SLS 2. 0 arc RB LGB RB A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 10/25

Magnet and power supply inventory SLS 2. 0 290. 4 m circumference = 62. 4 m straights + 228 m arcs 60 long. /trans. grad. compound bends, [VB|BN|VB] 0 (PM) 24 end magnets BE 0 (PM) 144 reverse bends AN 0 (PM) 96 quadrupoles QP 96 288 compound SOQ [sext. |{oct. +quad+skewquad}] 2 ( 24)+2 288 120 twin correctors CHV [CH+CV] 2 120 upgrade: 3 superbends VBS+BS+VBS: +9/-3, +3 738 magnets, 963 power supplies SLS 288 m circumference = 80 m straights + 208 m arcs 36 bending magnets BX, BE 2 174 quadrupoles QA/B/C[W] 174 120 sextupoles SR[W] {sext. +{CH+CV}(72), skewquad(36), aux. sext. (12)} 9+2 72+36+12 upgrade: 3 superbends BXS: +3/-3 bends, +6 PS upgrade: Femto insertion: +3 bends, +4 quads, +1 corr. H/V, +9 338 magnets, 392 power supplies A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 11/25

3. Machine Layout SLS: three-fold symmetry, i. e. periodicity 3 w 1997: small but heterogeneous user community § IR to hard X-ray, various polarizations, time resolved etc. . . w one ring for all users § . . . later, e. g. MAX IV: X-ray ring + UV ring + short pulse linac need for 3 long straights: § § § UV: long wavelength at high beam energy long undulators: l ~ l. U/E 2 FEMTO laser slicing insertion Machine: injection scheme based on 4 -kicker bump w SLS lattice layout: 12 arcs, 3 types of straights § 3 [long|arc|short|arc|medium|arc|short|arc] = 288 m circumference A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 12/25

SLS beam lines A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 13/25

Initial SLS 2. 0 design SLS 2. 0: keep all undulator positions periodicity 3 w actually no need for long straights • 1 L, Injection compact injection scheme based on anti-septum • 5 L, FEMTO/m. XAS laser beam slicing replaced by Swiss. FEL • 9 L, SIS since 2006 canted undulators for SIS & XIL split long straights: 1 11. 5 m 2 5. 0 m • incovenient for beam lines (4 canted undulators. . . ? ) w Circumference 287. 25 m = 478¾ l. RF (RF wavelength) § large RF detuning, complicated injection timing: l. RF, Ring l. RF, Booster w Bad dynamic aperture for non-zero chromaticity § non-zero chromaticity required for suppression of coupled bunch instabilities § Period-3: too many systematic betatron resonances near working point risk of insufficient injection efficiency and beam lifetime reject period-3 lattice establish period-12 lattice A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 14/25

SLS 2. 0 design after June 2016 SLS 2. 0: periodicity 12 w Much better beam dynamics performance § § negative chromaticity and good dynamic aperture all new rings have large periodicity: MAX IV: 20, ESRF-EBS: 32, ALS-U: 12, . . . w Leeway for further emittance reduction 137 99 pm. rad w Standardization and simplicity: 12 identical arcs [instead of 3+3+6]: § § magnet families: 4 [instead of 8] dipole, 4 [11] quadrupole, 7 [13] sextupole same vacuum components, supports, etc. w 12 identical straights of 5. 2 m § capacity for canted undulators: hard & soft X-ray, 2 mrad separation w Circumference 290. 4 m = 484 l. RF Local modification of tunnel wall § § A. Streun The 3 former long straights move out by 1. 8 m radially 9 of 12 straights almost stay in place: < 10 cm radial shift SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 15/25

Source point shifts L-straight (straights: midpoints) SLS 2. 0 S-s tra igh t radial and longitudinal shifts [mm] relative to SLS-now (without Femto) 12 288. 00 m 290. 40 m Harmonic number 480 = 25 3 5 484 = 22 112 3 L-straight L DR DS 11760 5210 1749 0 3 M-straight L DR DS 7000 5210 -29 0 6 S-straight L DR DS 4000 5210 77 1778 3 Superbend DR arc 2, 6, 10 DS A. Streun SLS 2. 0 machine -167 -206 ght 3 Periodicity Circumference rai SLS 2. 0 st M- SLS now Superbend 2/6/10 S longer BL 4/8/12 S shorter BL Beamline Proposal Workshop, Oct. 23 -24, 2018 16/25

Allocation of SLS and SLS 2. 0 straights A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 17/25

4. Storage ring parameters Main parameters of SLS 2. 0 (compared to SLS) w w Beam energy and current: 2. 4 Ge. V, 400 m. A (2. 4 Ge. V, 400 m. A) Circumference: 290. 4 m (288 m) Periodicity 12 (periodicity 3 ) Straights [available]: 12 [9½] 5. 2 m (6 [4] 4; 3 [2½ ] 7; 3 [2] 11½ m) w Horizontal emittance (including superbends) 101 pm (I = 0) 125 pm (400 m. A) (5500 pm) w Vertical emittance: 10 pm (5. . . 10 pm) w rms rel. energy spread ( 10 -3 ): 1. 04 (I = 0) 1. 08 (400 m. A) (0. 86) w Bunch length (FWHM) without with 3 HC: 23 70 ps (30 65 [40. . . 100] ps) w Beam pipe aperture: 20 mm (65 32 mm 2) w 500 MHz (500 MHz) RF system 484 (480) buckets A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 18/25

Vertical emittance w Ideal storage ring: vertical emittance very small (<1 pm) by nature w Real storage ring: some 10 pm due to errors. w SLS vertical emittance § § § 2010 campaign (TIARA) 1 pm (world record). user operation: 5. . . 10 pm. horizontal emittance 5000 pm emittance ratio 1: 1000 w SLS-2 vertical emittance § § 10 pm required to reduce bunch density: limit intrabeam scattering ( 25% emittance increase, with 3 HC) provide sufficient beam lifetime ( 8 hours, with 3 HC) Horizontal emittance 100 pm emittance ratio 1: 10 New domain of operation: development of scheme for controlled excitation of relatively large vertical emittance without coupling in straights, i. e. no visible beam tilt without degradation of dynamic aperture (lifetime, injection efficiency) feasible, but requires all 288 skew quadrupoles A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 19/25

Beam size: arc with superbend Pole-tip fields for r = 13 mm sy 10 mm 60 mm Dipol, B Quadrupole, B’r Sextupole, B”r 2/2 sx hse rms beam size (incl. IBS at 400 m. A) A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 20/25

Phase space and beam cross section for SLS 2. 0 and SLS electron beam only including diffraction at 20 ke. V (superbend 2. 9 T / 6. 0 T , zero fan angle) {x, x’} A. Streun {y, y’} SLS 2. 0 machine {x, y} Beamline Proposal Workshop, Oct. 23 -24, 2018 21/25

Beam stay clear Two undulators in straight: length 2 m, distance 0. 5 m Minimum gap horizontal 15 mm, vertical 4 mm Horizontal acceptance required for injection Vertical acceptance required for residual gas beam lifetime vertical horizontal half straight Nominal optics: wide beam • required for injection • little gain from focused beam for canted undulators • best working point A. Streun SLS 2. 0 machine “Low beta” optics: focused beam • feasible for quadrupoles • one, centered undulator - even smaller gap - higher brightness • not [yet] established Beamline Proposal Workshop, Oct. 23 -24, 2018 22/25

Undulator brightness Brightness of U 19 at SLS and SLS-2 Brightness scales with photon beam emittance (= electrons diffraction) 12 20 A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 23/25

Superbend flux and brightness Fan opening angle 0. 5 mrad convoluted into effective emittance Cave w Gaussian approximation of non-Gaussian w only relevant for micro-focusing experiments, not for full field imaging A. Streun SLS 2. 0 machine Brightness increase superbend 2. 9 T at SLS 20 ke. V 17 50 ke. V 67 100 ke. V 640 Beamline Proposal Workshop, Oct. 23 -24, 2018 6. 0 T at SLS-2 24/25

Conclusions 1. Confidence in SLS 2. 0 baseline design § competitive emittance despite small circumference • novel type of lattice (LGB/RB cell) § development of strong, compact magnets • extensive use of permanent magnets § 2. so far, no show stoppers Tunnel modification inevitable § § Increase of symmetry required to ensure performance Modifications confined to 3 long straight regions • minor/moderate modifications for the other 9 straights 3. Performance increase for experiments § 40 x lower emittance (at 400 m. A) • significant reduction of undulator source size and divergence • reduction of superbend source size and extension of X-ray spectrum § beam line growth potential • canted undulators in all straights, and many bending magnets A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 25/25

backup slides A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 26/25

LGB-RB cell example RB LGB QD QD RB LGB-RB cell (SLS-2 alternative lattice) exo= 103 pm 5° net deflection, 2. 48 m length. nx; y = 0. 428 (=3/7); 0. 143 (=1/7) By at x = 13 mm: dip, quad, total QF QD Dipol QD QF Conventional cell exo= 427 pm same deflection, length and tunes Optical functions LGB-RB Conventional Gain in radiation integrals: 1. 61 4. 14 1. 76 1. 45 A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 27/25

Michael Ehrlichman SLS-2 meeting, June 15 th, 2016 A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 28/25

Michael Ehrlichman SLS-2 meeting, June 15 th, 2016 A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 29/25

Flux and Brightness DLSR = diffraction limited storage ring “diffraction limited” means source (=electron beam) phase space << diffraction phase space maximum brightness theoretically possible full spatial coherence (point-like source) Photon beam phase space = convolution of diffraction phase space and electron beam phase space 2 -d phase space x x A. Streun SLS 2. 0 machine Area: Aspect ratio: [rms] (no correlation, xx’ = 0) emittance e x = sx beta-function b x = sx / sx size sx 2 = e x b x divergence sx 2 = e x / b x Beamline Proposal Workshop, Oct. 23 -24, 2018 30/25

Diffraction and electron phase space parameters Diffraction phase space Electron beam phase space Emittance Horizontal emittance in SLS ex = 5500 pm UPGRADE Horizontal emittance in SLS-2 ex 125 pm Vertical emittance in SLS & SLS 2 ey = 1. . 10 pm 10 ke. V 1. 24 Å er = 10 pm 1 ke. V 12. 4 Å er = 100 pm Beta-function of undulator source bru = L / 4 p* L = 1. . 5 m bru = 0. 08. . . 0. 40 m Beta-functions in undulators bx by = 1. . . 7 m Beta-function of dipole source Beta-functions in dipoles: brd = 0. 00134 m / B [T] bx = 0. 2. . . 0. 8 m B = 1. . 5 T brd = 0. 0003. . . 0. 00134 m by = 3. . . 20 m * R. Coïsson, Effective phase space widths of undulator radiation, Optical Engineering 27(3), 250 -252 (1988) A. Streun SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 31/25

Photon beam emittance Convolution of electron and diffraction phase space Example vertical photon phase space at 1 Å (12. 4 ke. V) at SLS (ey = 5 pm) for 2 m long undulator in short straight and for 2. 9 T superbend Phase space: electrons diffraction photons e y = 21 pm A. Streun SLS 2. 0 machine e y = 1100 pm Beamline Proposal Workshop, Oct. 23 -24, 2018 32/25

Bending magnet: horizontal fan emittance x s F F F x z w Filament beam source (fan angle 2 F) w Full field imaging experiments e. g. SLS/TOMCAT isotropic irradiation of large area (some cm 2) from almost-point-like source § large fan angle required w Micro-focusing experiments, e. g. SLS/PX-III equivalent 1 -s ellipse x r. F 2/2 diffraction divergence electron beam size A. Streun § SLS 2. 0 machine § loss in brightness due to fan emittance (very rough Gaussian approximation) § SLS: F = 1 mrad, r = 2. 76 m (2. 9 T superbend) exfan = 356 pm – compare to electron beam: SLS: ex = 5500 pm, SLS-2: ex = 137 pm Beamline Proposal Workshop, Oct. 23 -24, 2018 33/25

Critical feasibility issues Challenges for a low emittance ring in a very limited space w Dynamic acceptance: sufficient lifetime and injection efficiency § ok for period-12 lattice with discrete correctors w Beam current: stability with regard to impedances § probably ok (? ) for 500 nm NEG coating and 20 mm i beam pipe w Magnets: field strength, compactness and field quality § challenging – permanent magnet designs in an early stage § ok for the resistive coil magnets. w Girder system: positioning accuracy and stability ok w Vacuum system: compactness, pressure and impedance ok w Injection: efficiency and reliability in off-axis top-up operation A. Streun § ok with modified 3 -bump using “anti-septum” SLS 2. 0 machine Beamline Proposal Workshop, Oct. 23 -24, 2018 34/25