Ultimate Storage Rings PEP-X and SPring-8 II R. Hettel for the PEP-X design team and T. Watanabe et al., SPring-8 FLS 2012 JNAL March 7, 2012

PEP-II SPEAR3 2 km warm linac (33 GeV) + damping rings: PEP injection FACET LCLS 2 LCLS injector LCLS 1 km warm linac (16 GeV): LCLS 1 LCLS 2 What is the Future of X-ray Sources at SLAC?

PEP-X Design Study

E = 4.5 GeV I = 1.5 A  x = 150 pm-rad (~0.06 nm-rad w/o IBS)  y = 8 pm-rad  s = 3/6 mm (without/with 3rd harm rf)  = ~1 h top-up injection every few seconds (~7 nC, multiple bunches) PEP-X Baseline Concept (consolidated experimental halls) 2 arcs of DBA cells with 32 ID beam lines (4.3-m straights) 4 arcs of TME cells ~90 m damping wigglers 6 ea 120-m straights for injection, RF, damping wigglers long IDs, etc. Same coherent flux as 11-pm USR: higher emittance and current

PEP-X: Diffraction-Limited Storage Ring at SLAC 7BA cell Energy4.5-5 GeV Current200 mA Emittance (x/y)11/11 pm Bunch size (x/y, ID)7.4/7.4  m rms† Bunch length4 mm rms* Lifetime>2 h* Damping wigglers~90 m ID length (arc)~4 m ID length (straight)<100 m Beta at ID center, (x/y)4.92/0.8-5 m Circumference m Harmonic number3492 † Vertical beam size can be reduced towards 1  m *Harmonic cavity system would increase bunch length to ~8 mm and double the lifetime sufficient dynap for off-axis injection

Multibend Achromat Cells optimizing dynap and lifetime with ELEGANT M. Borland 7BA cell modified from MAX-4 cancelling all 3 rd and 4 th order resonances except 2 x -2 y Y.Cai et al., SLAC-PUB-14785, 2011

USRs - Spectral Brightness

USRs – Coherent Fraction

PEP-X Soft X-ray FEL in switched bypass E e- = 4.5 GeV  x,y = ~11 pm-rad FEL = 1 nm  = 80 pm-rad I pk = 300 ApkL ID = m P pk = few hundred kW rep rate: kHz Can inject special short, high peak current bunch to lase for a few turns

Preliminary studies show that radiation from m undulator whose first harmonic is tuned to 3.3 nm) would be enhanced by one to two orders of magnitude by the SASE FEL process acting with the stored beam. 30 nm 42 eV 3.3 nm 379 eV Soft X-ray Partial Lasing with Stored Beam in PEP-X Z. Huang, C. Pellegrini et al.

Option: 2-pass with 2.5-GeV linac PEP-X ERL – some options SCRF = 1.3 GHz “bunch ~ 1 MHz could drive FELs

SPring-8 II

Goal: - Significant improvement in light source performance, especially brilliance - In 2019 with 1 year shutdown - Cost range: approx. 40 billion Japanese yen “Boundary conditions”: - To take full advantage of existing resources >> Reuse the existing tunnel - ID beamline hutches should not be moved. - Same X-ray spectral range : a few to 100 keV - Good stability SPring-8 upgrade plans (from T. Watanabe)

A high-quality injection beam is needed. At SPring-8 we have XFEL Linac, which will be used as a full-energy injector to the storage ring. Energy: 8 GeV (max.) Emittance: 40 pm.rad Energy Spread: 0.01 % Bunch Length: 30 fs (rms) Electron Charge: 300 pC – 1 nC XFEL(SACLA) SR Booster Linac Parameters: (typical) 14 SPring-8 II – at-energy linac injector

4 – 6 GeV is the best 6 GeV is presently assumed, but GeV under consideration Intra-beam scattering (IBS) 6 GeV is better than 8 GeV up to 100+ keV SPring-8 II – electron energy

Natural emittance = 67 pm.rad ＋ Damping by ID's Damping wiggler Damping partition control Coupling control etc... Emittance = K (Electron energy) 2 (# bends) 3 X D SPring-8 II – 6-bend achromat lattice

SPring-8 II – damping by IDs and wigglers

SPring-8SP-8 II (planned) Electron energy8 GeV6 GeV Current100 mA~300 mA Emitance3.4 nm.rad67→10 pm.rad Energy spread0.0011~0.001 Coupling0.2 %~2 % Bunch length (rms)13 ps>20 ps Circumference1436 m # beamlines62 max.62+ max. * Parameters for SP8-II may be changed.

X 1000 Energy : 6 GeV Emittance: 35 pm.rad Coupling: 2 % Energy spread: 0.1% Current: 300 mA Brilliance: SPring- 8 vs. SPring-8 II

40ps 1ps XFEL SP-8 II ~10 fs Rough image: 1) ~ 1 ps, using x3.5 harmonic cavity 2) Should not affect extremely small emittance bunch Now under discussion with users SPring-8 II – possibility of short bunch operation

※ DA ~ ±3 mm A single device that enables both on- and off-axis injections SPring-8 II – new injection scheme

A quarter of the unit cell Beam Critical magnets Need R&D New vacuum design necessary SPring-8 II – strong multipole magnets

SPring-8 II – new RF system

e-bunch needs to be lengthened for lifetime and less IBS effect New higher harmonic RF system enables it. SPring-8 II – harmonic RF system

Sextupole alignment error:  = 10  m, cutoff = +/-20  m Dynamic aperture with 20um SX errors SPring-8 II – dynamic aperture

- Goal: ~10pm.rad = ultimate storage ring - Planned for 2019 with one-year shutdown - Take full advantage of existing resources - Now under extensive studies for lattice design and technology developments - Challenging issues clarified - New components proposed and studied, but need more - A couple of design alternatives. Open to any change. - R&D will start in FY2012 SPring-8 II – Summary