Design, status and roadmap of next
generation low emittance ring
R. Bartolini
Diamond Light Source
and
John Adams Institute, University of Oxford
Thanks to B. Hettel and M. Borland
ESLS XXII Workshop
Grenoble, 25 November 2014
Outline
• Overview of machine upgrade programmes (2010 vs 2014)
• Short survey of new ring desing
• Challenges in design and technology of ultra low emittance rings
• Matching users requests and conclusions
ESLS XXII Workshop
Grenoble, 25 November 2014
New rings and upgrades R&D programmes (2014)
MAX-IV
Spring-8 II
PEP-X
APS
USR
330 pm
70 pm (48)
5 pm
100 pm (25)
3 pm
3 GeV
6 GeV
6 GeV
7 GeV
9 GeV
7BA
6BA
7BA
7BA
7BA
SIRIUS
ESRF II
Diamond II
ALS
BAPS
280 nm
140 pm (28)
140-270 pm (20-10)
100 pm (20)
50 pm
3 GeV
6 GeV
3 GeV
2 GeV
5 GeV
TBA
USR Beijing 12
7BA-hybrid
(270 pm DDBA - 140 pm 5BA)
9BA
10BA
SOLEIL
SLS
ELETTRA
ANKA
CLS
SPEAR III
430 pm (10)
250 pm (20)
250 pm (28)
5000 pm (18)
800 pm (22)
750 pm (13)
2.7 GeV
2.4 GeV
2 GeV
2.5 GeV
2 GeV
3 GeV
IPAC13-14
DB-split
Longitudinal gradient bend
6BA
split-TME
7BA
DQBA
ESLS XXII Workshop
Grenoble, 25 November 2014
IPAC 11-12
Upgrade programmes ~ 2010
Up until ~2010 upgrade of existing third generation light sources targeted
e.g .ESRF purple book
• Lower vertical emittance (lower coupling)
• Longer straight sections (longer IDs or canted Ids)
• Higher current (from 200 mA to 300 mA)
• Top Up for 16 and 4 bunches modes
• New technology: CPMU, RF NC HOM free cavities, SS amplifiers, BPMs.
e.g. APS studies
• ERL option
• other intermediate upgrades options (not precluding the ERL option):
• Longer straight sections (longer IDs, customized optics, canted Ids)
• Higher current (from 100 mA to 200 mA)
• Short pulses programme with crab cavities,
• Increase BW of orbit feedback system to achieve sub-m stability up to 200 Hz
ESLS XXII Workshop
Grenoble, 25 November 2014
Why now ?
• Science case is growing: NSLS-II, MAX-IV, APS, Spring-8, ESRF, …
science enabled by better photon properties
• Growing confidence in “aggressive” low emittance lattice designs
from DBA to MBA
injection in smaller apertures (…eventually on axis)
• Excellent control of the beam properties proven at many light sources
orbit, optics, stability, lifetime, losses, customised optics…
beam based tuning tools
• Key enabling technologies appear to be mature
no showstoppers in magnets, vacuum, diagnostics, RF, …
ESLS XXII Workshop
Grenoble, 25 November 2014
Science case
A number of workshop have discussed the science case for ultra low
emittance lattices
XDL 2011 Workshops for ERLs and DLSRs, Cornell, June 2011
Beijing USR Workshop, Huairou, October 2012
DLSR Workshop, SPring-8, December 2012
DOE BESAC Subcommittee on Future Light Sources, July 2013
SLAC DLSR Workshop, SLAC, December 2013
DLSR Workshop, Argonne, November 2014
A dedicated issue in Journal of Synchrotron Radiation is in publication
High brilliance and transversely coherent x-rays
- Uniform phase wavefronts: coherent imaging, holography, speckle, etc.
- Focusable to smallest spot size: nano-focus
- High flux (~1014-1015 photons/sec) in small spot: slits may not be required, etc.
- Round beams: H-V symmetric optics, circular zone plates, flexibility in optics
ESLS XXII Workshop
Grenoble, 25 November 2014
Lattice design
Growing confidence in “aggressive” low emittance lattice design
• Lattice design evolution from DBA, TBA to 4BA,…MBA:
• Lattice optimisation tools improved (linear and nonlinear dynamics)
Low emittance lattice require small angle bending
2
x 
 H  dipole
Jx 
H(s)  D 2  2DD'D' 2
Minimise  and D and be close to a waist in the dipole
 x  C q F 2 3 
1
N 3d
MBA lattices (large rings favoured)
ESLS XXII Workshop
Grenoble, 25 November 2014
Multiple bend achromats
DBA
7BA
Dispersion Function
1/2 Insertion Straight
1/2 Insertion Straight
Achromat
Simplified explanation
– Emittance is driven by randomness of photon emission in presence of dispersive
(energy-dependent) orbits – electron recoils randomly
– Breaking up dipoles and putting focusing (quadrupoles) between the parts allows
reducing the amplitude of dispersive orbits – smaller electron recoils
ESLS XXII Workshop
Grenoble, 25 November 2014
Design challenges
 Linear optics
– To reduce the amplitude of dispersive orbits, must bend more gently (small
bending angles) and focus more frequently and more strongly
– Finding good optics with existing layout constraints is non trivial
 Focusing (quadrupole) elements have chromatic aberrations
– Sextupole magnets added to correct these
– Introduces higher order aberrations that must be corrected
– Require magnets with small bore radia
 Stronger focusing leads to difficult non-linear dynamics
– Poor “momentum aperture”  reduced lifetime  frequent injection
– Poor “dynamic aperture”  greater difficulty injecting
– Some designs are considering on-axis injection
 Collective instabilities are amplified with short bunches
ESLS XXII Workshop
Grenoble, 25 November 2014
Optimisation of beam dynamics
ESLS XXII Workshop
Grenoble, 25 November 2014
Lattice designs
MAX–IV (Sweden) is taking the first pioneering
step with 7BA, under construction
3 GeV, 528 m, 0.25 nm
Sirius (Brazil) just started construction of
5BA with superbend
3 GeV, 518 m, 0.28 nm
L. Liu, LNLS.
Lattice designs
ESRF (France)
6 GeV, 844 m, 4 nm → 150 pm
now - ESRF DBA
• Dispersion bumps for efficient sextupoles
• Longitudinal gradient dipoles (D1, D2,
D6, D7) to further reduce emittance
• Combined dipole-quadrupoles D3-4-5
• 3-pole wiggler as hard X-ray source
APS (US - preliminary)
7 → 6 GeV, 1104 m, 3.1 nm → ~65 pm
• ESRF-style lattice, 3-pole wiggler
• Swap-out injection
• Superconducting undulators
SPring-8 (Japan)
8 → 6 GeV, 1436 m, 2.8 nm → <100 pm
•lattice under development
future - ESRF 7BA
Lattice designs
ALS-U (US - LBNL)
1.9 GeV, 200 m, 2 nm → 52x52 pm
• 9BA
• Swap-out injection from accumulator ring
• 3-T PM superbend insertions
Other rings:
•SLS (Switzerland - PSI)
2.4 GeV, 288 m, 5 nm → 0.25 nm
•Soleil (France)
ALS-II swap-out/accumulator
2.75 GeV, 354 m, 3.9 nm → 0.5 nm
…..
ALS-U 24-mm ID chamber
ESLS XXII Workshop
Grenoble, 25 November 2014
A modified 4BA lattice for Diamond-II
• Increase dispersion at chromatic sextupoles
• Optimize magnets positions and length leaving more distance between dipoles
(no coil clash)
• removed sextupoles in the new straight
• Longer mid-cell straight section from 3m to 3.4 m – longer is unmanageable
ESLS XXII Workshop
Grenoble, 25 November 2014
upgrade with Diamond-II (200pm):
300mA and 1%K
Brilliance plot using U27 – 72 periods 2 m long with Kmax = 2.02
Tuning curves computed with Spectra 8.0
ESLS XXII Workshop
Grenoble, 25 November 2014
Survey of low emittance lattices
ESLS XXII Workshop
Grenoble, 25 November 2014
Experimental control of the beam optics
Growing confidence in the experimental control of the electron optics
Proven correction strategies
beam based tuning techniques
(better instrumentation: diagnostics, power supplies, …)
e.g. Diamond operates with a very good control of the beam optics
• Optics deviation (beta-beating) redecue to 1% level
• Emittance [2.78 - 2.74] (2.75) nm
• Energy spread [1.1e-3 - 1.0-e3] (1.0e-3)
• Emittance coupling ~0.08% achieved → vertical emittance ~ 2.0 pm (2009 WR)
6 m rms vertical
Records for smallest vertical emittance (2011-2014)
SLS
0.9 pm
Courtesy L. Rivkin
PSI and EPFL
APS
0.35 pm
ESLS XXII Workshop
Grenoble, 25 November 2014
Comparison machine/model and
Lowest vertical emittance (back in 2011)
Model
emittance
Measured
emittance
-beating (rms)
Coupling*
(y/ x)
Vertical
emittance
ALS
6.7 nm
6.7 nm
0.5 %
0.1%
4-7 pm
ASP
10 nm
10 nm
1%
0.01%
1-2 pm
2.74 nm
2.7-2.8 nm
0.4 %
0.08%
2.0 pm
4 nm
4 nm
1%
0.1%
3.7 pm
SLS
5.6 nm
5.4-7 nm
4.5% H; 1.3% V
0.04%
2.0 pm
SOLEIL
3.73 nm
3.70-3.75 nm
0.3 %
0.1%
4 pm
SPEAR3
9.8 nm
9.8 nm
< 1%
0.05%
5 pm
SSRF
3.9 nm
3.8-4.0 nm
<1%
0.13%
5 pm
Diamond
ESRF
Since these early studies
* best achieved 2011
SLS reached 0.9 pm V emittance
Diamond is providing 8 pm V emittance in users’ operation
ESRF is providing 8 pm V (and lower) emittance in users’ operation
Enabling technology
Compact magnet and vacuum technology
• Precision magnet pole machining for small aperture magnets, combined
function magnets, tolerance for magnet crosstalk (e.g. MAX-Lab)
• NEG-coated vacuum chambers enable small apertures to enable high magnet
gradients
Pioneered at CERN, used extensively at Soleil, and adopted for MAX-IV and
Sirius MBA lattices
MAX-IV
Courtesy S. Leemans
heater tape for
in-situ NEG
Diamond,
11 July 2014
bake-out Sirius
SPring-8
concept
K. Soutome
Enabling technology
Other advances in accelerator and light source
technology:
• Fast kickers for on-axis injection
Fast kickers (KEK ATF)
• Sub-micron e- BPMs with micron resolution single
pass capability: non-linear lattice tuning
Higher order
resonances
detected by
turn-turn BPMs
• Accelerator and beam line component mechanical
positioning and stabilizing systems
(A. Franchi)
• “In-situ” and beam-based magnet measurement and
alignment methods
• Mode-damped RF cavities (fundamental and harmonic)
• Highly stable solid state RF power sources
• High performance IDs (superconducting,
Delta, RF, etc.)
• Advances in X-ray optics and detectors
start-to-end beam line system simulations, SC
detectors, cryo-cooled mirrors, etc.
SPring-8 concept based on NSLS-II
vibrating wire method - K. Soutome
Delta undulator
prototype - A. Temnykh
SC undulator development at
LBNL (S. Prestemon et al.), APS
(E. Gluskin et al.) and elsewhere
Conclusions
Many 3GLS operates since 2000’s with nominal parameters
•
few nm H emittance
•
300-500 mA
•
8pm V emittance
However:
– 2010 Petra-III was commissioned  1 nm H emittance
– 2011-12 SLS and ASP ~1 pm V emittance (best achieved)
– 2012 ESRF et al. operate with 8pm V emittance
– 2013 ALS upgraded to a 2 nm H emittance lattice
– 2014 NSLS-II started operation  0.5 nm H emittance
– 2014 Petra III has tested a 160 pm lattice at 3GeV
– 2016 MAX IV 300 pm H emittance lattice
– 2019 ESRF II 140 pm H emittance lattice
ESLS XXII Workshop
Grenoble, 25 November 2014
Conclusions
Man 3GLS are investigating a full ring upgrade (Diamond–II, SLS-II, SOLEIL,
…)
Various MBA options are under analysis.
Some of the designs have still lots of flexibility in the technical choices
Need input from PBSs and Users
what emittance?
are round beams needed?
alternate high beta – low beta ?
operating modes (e.g. low alpha, …)?
… open for any exotic ideas?
AP should explore tailoring the design to their specific beamlines
ESLS XXII Workshop
Grenoble, 25 November 2014
Low emittance ring community
The development of ultra low emittance rings is now seriously tackled by a
large community, including damping rings and HEP colliders meeting
regularly in workshop discussing general or dedicated topics (beam
dynamics, collective effects, technology for low emittance rings
• ICFA Low Emittance Rings Workshops (LowERing)
• XDL 2011 Workshops for ERLs and DLSRs, Cornell, June 2011
• Beijing USR Workshop, Huairou, October 2012
• DLSR Workshop, SPring-8, December 2012
• Low Emittance Ring Workshop, Oxford, July 2013
• SLAC DLSR Workshop, SLAC, December 2013
• Workshop on Low Emittance Rings Technology (ALERT 2014), Valencia, 2014
• Low Emittance Rings Workshop (LER2014), Frascati, September 2014
• DLSR Workshop, Argonne, November 2014
ESLS XXII Workshop
Grenoble, 25 November 2014