Emittance Gymnastic Studies P.Raimondi On behalf of the Accelerator and Source Division ESRF June 15,2012
Outline - Introduction to 4 th generation SR - ESRF toward a 4 th generation SR - ASD Short and Mid term path - Conclusions 2
The 4 th Generation SR The last few years have been characterize by a World-Wide R&D carried on by Accelerator Engineers to find solutions to improve the SR beam parameters. The Science in general benefits by any of this improvements: - Horizontal Emittance - Vertical Emittance => Diffraction Limit reached routinely everywhere - Bunch Length => Very costly solutions (e.g. SC Crab Cavities) - Energy Spread => No solutions exists for a significant decrease (< 0.05-0.1%) in SR - Beam Current => Close to the limits imposed by the BL 3
Low Horizontal Emittance SR The most immediate advantages of such machines are: - Brigthness Increase while maintaining the same flux - Spacial Resolution Increase - Transverse Coherence The first two points improve almost linearly for an emittance decrease from 2-4nm down to 50-100pm. For lower emittance the gain become less than linear due to: - the diffraction limit - mismatch of the electron beam with the X-Ray beam The coherence starts to be of significance for emittances below 5-10pm. For example: @10KeV 80% coherence needs about 1pm emittance. 4
Brilliance at lower horizontal emittance 6 m Undulators , min. gap=11 mm (U35, HU88) 23 10 4 m In-Vacuum undulators, min. gap=6 mm (IVU22, CPMU18) ~ x 5 Electron beam: 6.039 GeV 22 10 I=0.2 A 2 2 /mr Ph/s/0.1%bw/mm ~ x 25 21 10 20 10 4 5 6 7 8 9 2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 1 keV 10 keV 100 keV Photon Energy [eV] Hor. Emittance [nm] 4 0.15 0.01 Vert. Emittance [pm] 3 2 2 Energy spread [%] 0.1 0.09 0.09 Betax[m]/Betaz [m] 37/3 6/2 6/2 5 J.Chavanne
USRs – Coherent Fraction Coherent Fraction 1.E+00 7 3 1.E-01 6 4 2 coherent fraction 5 1 ALS upgrade: 2200 x 30 pm 1.E-02 1 2 NSLS-II: 600 x 8 pm 3 MAX-IV: 260 x 8 pm 1.E-03 4 SDLS: 40 x 40 pm 5 USR7: 15 x 15 pm 1.E-04 6 PEP-X: 11 x 11 pm 7 TevUSR: 1.3 x 1.3 pm 1.E-05 0.01 0.1 1 10 100 photon energy (keV )
Brilliance vs Hor. Emittance & Energy Spread Undulator: CPMU18, L=4m ESRF today =1 Betax=4.5m, betaz=2.5m No dispersion Vertical emittance= 3pm 1.0x10 -3 1.0x10 -3 100 80 10 2 30 5 0 0.8 2 0.8 40 Relative Energy Spread [] 60 Relative Energy Spread [] 0.6 1 0.6 5 0 10 5 2 20 30 2 0 0.4 0 0.4 3 0 0 40 60 80 100 0.2 120 0.2 500 2 3 4 5 6 7 2 3 4 5 6 7 2 3 4 2 3 4 5 6 7 2 3 4 5 6 7 2 3 4 0.01 0.1 1 0.01 0.1 1 Horizontal emittance [nm] Horizontal emittance [nm] Fundamental (n=1) Harmonic # 9 J.Chavanne 7
All solutions to Lower the SR Horizontal-Emittance are based on this formula! 8
PEP-X 40pm@4.5GeV Multibend Achromat Cells 7BA cell modified from MAX-4 cancelling all 3 rd and 4 th order resonances except 2 n x -2 n y optimizing dynap and lifetime Y.Cai et al., SLAC-PUB-14785, 2011 with ELEGANT M. Borland
ESRF toward a 4 th Generation SR The world wide effort in lattice design and technology developments has paved the road the possibility of studying options to upgrade the ESRF storage ring lattice in order to significantly lower (by a factor 20-40) the equilibrium horizontal, within the constraints underlined in the ESRF “purple book” (par. 3.1.8) , in particular: - Maintain as much as possible unchanged the existing Straight Sections and BeamLines - Maintain the present Injection Scheme and Injection Complex - Reuse as much as possible the existing ARCs hardware (Power Supplies, Vacuum System, Diagnostic etc…) - Reduce Operation Costs, specifically Wall-Plug Power. These constraints pose limits to the ultimate ring performances and raise technical and logistic challenges. On the other end they are consistent with the following crucial points: - Cost comparable with a “Phase II” budget expenditure - Upgrade to be completed by beginning of next decade (2020) - Less than 1 year ShutDown for installation and commissioning 10
Present ESRF lattice n x = 2.277 1 period Low emittance: n z = 0.837 C= 52.774 Careful tuning of 𝛾 x and 60 0.6 b x 𝜃 x in the dipoles (where b z the radiation occurs) h x 50 0.5 𝛾 x : envelope function 𝜃 x : dispersion 40 0.4 b [m] h [m] 30 0.3 20 0.2 10 0.1 0 0 0 5 10 15 20 25 s [m] 03/05/2012 L. Farvacque 11
Present ESRF lattice n x = 2.277 1 period Low emittance: n z = 0.837 C= 52.774 Careful tuning of 𝛾 x and 60 0.6 b x 𝜃 x in the dipoles (where b z the radiation occurs) h x 50 0.5 𝛾 x : envelope function 𝜃 x : dispersion 40 0.4 b [m] h [m] 30 0.3 e x = K g 2 q 3 20 0.2 10 0.1 K : lattice dependent 𝛿 : electron energy 𝜄 : bending angle 0 0 0 5 10 15 20 25 s [m] 03/05/2012 L. Farvacque 12
Present ESRF lattice n x = 2.277 1 period Low emittance: n z = 0.837 C= 52.774 Careful tuning of 𝛾 x and 60 0.6 b x 𝜃 x in the dipoles (where b z the radiation occurs) h x 50 0.5 𝛾 x : envelope function 𝜃 x : dispersion 40 0.4 b [m] h [m] 30 0.3 e x = K g 2 q 3 20 0.2 10 0.1 K : lattice dependent 𝛿 : electron energy 𝜄 : bending angle 0 0 0 5 10 15 20 25 s [m] • Increase the number of cells Emittance reduction ⇒ • Put more dipoles per cell 03/05/2012 L. Farvacque 13
New lattice e x = 4 nm n x = 2.277 1 period n z = 0.837 C= 52.774 60 0.6 b x b z DBA h x 50 0.5 40 0.4 h [m] b [m] 30 0.3 20 0.2 10 0.1 0 0 0 5 10 15 20 25 s [m] 03/05/2012 L. Farvacque 14
New lattice e x = 4 nm e x = 0.13 nm n x = 2.277 1 period n x = 4.729 2 periods n z = 0.837 C= 52.774 n z = 1.725 C= 52.801 60 0.6 60 0.6 b x b x b z b z DBA h x 7-bend achromat h x 50 0.5 50 0.5 40 0.4 40 0.4 h [m] h [m] b [m] b [m] 30 0.3 30 0.3 20 0.2 20 0.2 10 0.1 10 0.1 0 0 0 0 0 5 10 15 20 25 0 5 10 15 20 25 s [m] s [m] 03/05/2012 L. Farvacque 15
New lattice e x = 4 nm e x = 0.13 nm n x = 2.277 1 period n x = 4.729 2 periods n z = 0.837 C= 52.774 n z = 1.725 C= 52.801 60 0.6 60 0.6 b x b x b z b z DBA h x 7-bend achromat h x 50 0.5 50 0.5 40 0.4 40 0.4 h [m] h [m] b [m] b [m] 30 0.3 30 0.3 20 0.2 20 0.2 10 0.1 10 0.1 0 0 0 0 0 5 10 15 20 25 0 5 10 15 20 25 s [m] s [m] • Cell packed with magnets • Stronger focusing: tunes → 36.44/13.39 75.66/27.60 • → Chromaticity: -130/-58 -102/-75 } ⇒ { • Smaller 𝛾 functions Chromaticity correction needs • Smaller dispersion stronger sextupoles • Less radiated power (x2 less) 03/05/2012 L. Farvacque 16
New lattice n x = 2.364 1 period n z = 0.863 C= 26.400 Preliminary features: 20 0.1 b x b z 18 0.09 • 2 dipole families h x • 1 with gradient 16 0.08 • 14 0.07 7 quadrupole families 12 0.06 • 2 sextupole families b [m] h [m] 10 0.05 • ID straight: 8 0.04 5 m long instead of 6 0.03 7.84 m (in “6 m” section) 4 0.02 • No more alternating high- 2 0.01 and low- 𝛾 sections 0 0 0 5 10 15 20 25 s [m] Electron beam size [µm] Electron beam divergence [µrad] ESRF New ESRF New High- 𝛾 High- 𝛾 412 11 28 5 Low- 𝛾 Low- 𝛾 50 107 03/05/2012 L. Farvacque 17
New Lattice ESRF New lattice Dipole [T] 0.86 0.49 Quadrupole [T/m] 17 (25) 112 Sextupole [T/m2] 460 1650 • Weak bending magnet with strong gradient • Equivalent to a quadrupole of 33 T/m offset by 1.5 cm • Strong quadrupoles • Strong sextupoles • Dynamic aperture comparable (factor 1-3 smaller) with the present lattice - Chromatic correction made with “standard”sextupoles - Total bend length more than doubled => energy lost in synchrotron radiation halved 03/05/2012 L. Farvacque 18
Quadrupole Magnet Design G> 100T/m EM quadrupole PM quadrupole Solutions Compatible with a “Soleil - type Vacuum Chamber” 19
New Lattice Engineering The complexity of the problem is relatively contained, since it is limited only to the design of a 25m long Arc (*32). However the technical aspects are very challenging: - High gradients magnets (4 times more) - Tight tolerances (2 times more) - Small vacuum chamber (2 times less) - Very compact design It should be stressed that the 4 th Generation SRs take advantage of all the R&D and Know-How accumulated in the last 20 years at ESRF and the rest of the world: - Lattice design - Vacuum technologies (e.g. NEG coating that allows the use of smaller vacuum chambers) - Magnet technologies (better modeling and manufacturing) - Diagnostic (e.g. Libera BPMs) - Controls - Operations - … 20
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