Recent Developments at Diamond Ian Martin On behalf of the Diamond Team Particle Accelerators and Beams Group Meeting Daresbury Laboratory 10 th April 2013

 Diamond overview  ARPES beam line  Reduced coupling operation  Low alpha with top-up  Improved current stability  Improved CSR spectral stability  Possible future upgrades  Diamond II options  Modifying a single cell of existing ring  Conclusions Ian Martin IOP PAB Group meeting, DL, (April 2013) Talk Outline

 3 rd Generation Synchrotron Light Source  100 MeV Linac  3 GeV booster synchrotron (158.4m)  3 GeV storage ring (561.6m)  Mix of BM and ID beamlines (long and standard straight sections) Overview of Diamond Ian Martin IOP PAB Group meeting, DL, (April 2013)  Several modes of operation (all top-up):  Standard (900 bunches / 300mA)  Hybrid (686 bunches / 300mA + 1 bunch / 3mA)  Two low-alpha modes (Short x-ray pulse / THz users)

Overview of Diamond Ian Martin IOP PAB Group meeting, DL, (April 2013) Operational (15 ID, 4 Dipole) Optimisation (4 ID) Construction (4 ID, 2 Dipole) Design (3 ID, 1 Dipole) Anticipate all straights assigned and operational by 2017

Ian Martin IOP PAB Group meeting, DL, (April 2013) ARPES (I05) Undulator For the ARPES beamline, a 5m long APPLE-II device was installed in Nov 2012:  Long straight section, beta functions larger than standard  Large tune-shifts in both planes that need to be compensated  Significant impact on the machine (reduction in dynamic aperture, lifetime) Photon Energy eV Device Period140 mm Number of Periods34 Nominal Length4.995 m TechnologyAPPLE-II Minimum Gap23.5 mm Peak Field0.9T (H) / 0.53T (C) / 0.63T (V) Magnetic MaterialNdFeB

Ian Martin IOP PAB Group meeting, DL, (April 2013) ARPES (I05) Undulator Dynamic multipole fields compensated using active shim wires Active shim wires Insertion device Residual kick Tune Shift (ΔQ x / ΔQ y )Beta Beat (x / y) Vertical Polarisation Uncorrected / % / 32% Corrected0.003 / % / 3% Circular Polarisation Uncorrected / % / 23% Corrected0.005 / % / 2% Horizontal Polarization Uncorrected / % / 13% Corrected0.008 / % / 6%

Ian Martin IOP PAB Group meeting, DL, (April 2013) Reduced Vertical Emittance In response to request from Science Division, emittance coupling has been reduced from 1% to 0.3% for user operation (27 pm.rad to 8 pm.rad)  Initially confined to machine development periods  Two week period from 17 th October to 1 st November 2012  Standard operational mode since 6 th March 2013 Benefits include increased brightness / transverse coherence, smaller spot size 1% coupling 0.3% coupling

Ian Martin IOP PAB Group meeting, DL, (April 2013) Reduced Vertical Emittance couplinglifetimecurrent Coupling feedback started

Ian Martin IOP PAB Group meeting, DL, (April 2013) Reduced Vertical Emittance Reducing vertical emittance leads to small focus on sample Courtesy K. Sawhney

Ian Martin IOP PAB Group meeting, DL, (April 2013) Reducing vertical emittance leads to higher spatial coherence Reduced Vertical Emittance Courtesy K. Sawhney

Low Alpha Short Pulse ModeTHz Mode Momentum Compaction Factor-1× ×10 -6 Number of bunches Bunch current50 µA (93 pC) Emittance coupling ratio0.3%1% Lifetime~20h Injection efficiency (IDs open)30-40%15-20% V RF 3.4MV Micro-bunching instability threshold (SB)~30-35 µA~15 µA Bursting threshold (SB)~55-60 µA~25-30 µA The Diamond storage ring is run in a dedicated ‘low alpha’ mode 2-3 times per year Since Oct 2012, this has been in top-up with hourly injection cycles Short pulse mode (NANOSCIENCE beamline I06):  Single bunch for time-resolved science  Electron bunch length reduced to ~3.5 ps  Priority on increased single bunch charge over minimum pulse duration (stable!) THz mode (MIRIAM beamline B22):  Above bursting threshold to increase CSR gain in THz region  Priority to extend CSR spectrum towards 100cm -1 Ian Martin IOP PAB Group meeting, DL, (April 2013)

03/10/201204/10/201205/10/2012 Courtesy G. Cinque MIRIAM (B22) Spectrum Ian Martin IOP PAB Group meeting, DL, (April 2013)

Ian Martin IOP PAB Group meeting, DL, (April 2013) Diamond Upgrade Starting to take a look at possible options for a future upgrade of the Diamond lattice*  Initial criteria  Reuse tunnel and beamlines  Reuse as much hardware as possible  Phased installation (avoid long shutdown)  Different ‘flavours’ under consideration  Evolution of 4 Bend Achromat (BA), 5BA, 7BA,...  More beamlines vs. lower emittance *see poster by T. Pulampong

Ian Martin IOP PAB Group meeting, DL, (April 2013) 4 Bend Achromat  Magnet arrangement allows 24 additional short straight sections  Natural emittance 275 pm.rad (factor 10 reduction on present lattice)  Magnets and vacuum design challenging (high gradients / small apertures)  Design utilises gradient bending magnets  Harmonic number lowered by 1 to minimize transverse offset for existing beamlines (circumference reduced from 561.6m to 561.0m) 3.35m Original DBA 4BA Modified 4BA

 Length of existing straight sections reduced to accommodate additional magnets  Natural emittance 155 pm.rad (factor 17 reduction on present lattice)  Phase advance across two cells matched to odd integer to help cancel sextupole driving terms and increase dynamic aperture (~4mm): Ian Martin IOP PAB Group meeting, DL, (April 2013) 5 Bend Achromat Original DBA 5BA

emittance to be maintained Ian Martin IOP PAB Group meeting, DL, (April 2013) 7 Bend Achromat Original DBA 7BA  Natural emittance 45 pm.rad (factor 58 reduction on present lattice)  Basic design includes dispersion bump between dipoles 1-2 and 6-7 to ease correction of natural chromaticity  Maximum sextupole strength factor 2 lower as a result  Intra-beam scattering places upper limit on beam current that still allows low

Ian Martin IOP PAB Group meeting, DL, (April 2013) MBA Comparison Existing DBAModified 4BA5BA7BA Circumference (m) Natural Emittance (pm.rad) Tune Point (Q x / Q y )27.20 / / / /52.17 Natural Chromaticity (ξ x / ξ y )-80.4 / / / / -119 Momentum compaction1.66× × × ×10 -4 Max Quad. Strength (m -2 )<2 (1.99)< 7 < 10 Max Sext. Strength (m -3 )<35 (20.0)< 380< 700< 326 Emittance with IBS* (pm.rad) Length of straight sections # (m)11.3 / / 6.7 / / / 5.0 *Intra-Beam Scattering calculated using ELEGANT for 450mA / 900 bunches / 10% coup / 3.3MV # Quadrupole to quadrupole separation

Ian Martin IOP PAB Group meeting, DL, (April 2013) ‘DIAD’ Beamline Dual Imaging and Diffraction (DIAD) beamline requires high flux in the 4-40keV range Considering replacing existing cell with a modified 4BA cell  Introduces an additional straight section (bending magnet beamline upgraded to ID beamline)  Serves as a prototype for low emittance lattice upgrade  In line with phased upgrade  Lots of R&D required (magnet design challenging, vacuum with small apertures, engineering integration, etc) Still work in progress; need to find solution with adequate dynamic aperture and lifetime before it could be considered. Other options include modified DBA cell or replacing second bending magnet with a 3T normal conducting super-bend. modified 4BA cell Additional straight

Work at Diamond is continuing on different fronts, partly by increasing the capacity of the facility by adding new beamlines, but also by upgrading existing beamlines and improving the performance of the accelerator itself (e.g. improving MTBF, reducing coupling, increasing beam current, beam stability,...) Other current topics not mentioned so far:  Low emittance optics for existing lattice  Girder re-alignment program  ‘COLDDIAG’ – diagnostic device to study head load on cryogenic surfaces  Fast polarisation switching during user time (I10)  Increasing beam current (350mA tests soon, working towards 500mA)  4 th RF cavity Ian Martin IOP PAB Group meeting, DL, (April 2013) Conclusions

ARPES (I05) S. Mhaskar, E. Longhi, B. Singh, R. Fielder, R. Bartolini Reduced Coupling Studies D. Hicken, M. Abbott, C. Thomas, R. Bartolini, K. Sawhney Low Alpha R. Bartolini, G. Cinque, M. Frogley, P. Karataev, A. Morgun, G. Rehm, W. Shields, C. Thomas, R. Walker Diamond Upgrade R. Bartolini, C. Bailey, M. Cox, N. Hammond, R. Holdsworth, J. Jones, J. Kay, L. Malysheva, N. Marks, S. Mhaskar, T. Pulampong, R. Walker,... Ian Martin IOP PAB Group meeting, DL, (April 2013) Acknowledgements