Recent Developments at Diamond

Ian MartinOn behalf of the Diamond Team

Particle Accelerators and Beams Group MeetingDaresbury Laboratory

10th 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 MartinIOP PAB Group meeting, DL, (April 2013)

Talk Outline

3rd 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 MartinIOP 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 MartinIOP 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 MartinIOP 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 standardLarge tune-shifts in both planes that need to be compensatedSignificant impact on the machine (reduction in dynamic aperture, lifetime)

Photon Energy 18-240 eVDevice Period 140 mmNumber of Periods 34Nominal Length 4.995 mTechnology APPLE-IIMinimum Gap 23.5 mmPeak Field 0.9T (H) / 0.53T (C) / 0.63T (V)Magnetic Material NdFeB

Ian MartinIOP PAB Group meeting, DL, (April 2013)

ARPES (I05) Undulator

Dynamic multipole fields compensated using active shim wires

-40 -20 0 20 40

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Active shim wiresInsertion deviceResidual kick

Tune Shift (ΔQx / ΔQy) Beta Beat (x / y)

Vertical Polarisation

Uncorrected -0.043 / 0.032 33% / 32%Corrected 0.003 / 0.003 3% / 3%

Circular Polarisation

Uncorrected -0.030 / 0.026 22% / 23%Corrected 0.005 / 0.004 2% / 2%

Horizontal Polarization

Uncorrected -0.003 / 0.015 2% / 13%Corrected 0.008 / 0.008 5% / 6%

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Ian MartinIOP PAB Group meeting, DL, (April 2013)

Reduced Vertical Emittance

x (mm)

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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 17th October to 1st November 2012 Standard operational mode since 6th March 2013Benefits include increased brightness / transverse coherence, smaller spot size

1% coupling 0.3% coupling

Ian MartinIOP PAB Group meeting, DL, (April 2013)

Reduced Vertical Emittance

coupling lifetime current

Coupling feedback started

Ian MartinIOP PAB Group meeting, DL, (April 2013)

Reduced Vertical Emittance

Reducing vertical emittance leads to small focus on sampleCourtesy K. Sawhney

Ian MartinIOP PAB Group meeting, DL, (April 2013)

Reducing vertical emittance leads to higher spatial coherence

Reduced Vertical Emittance

Courtesy K. Sawhney

Low Alpha

Short Pulse Mode THz ModeMomentum Compaction Factor -1×10-5 -4.5×10-6

Number of bunches 400 + 1 200Bunch current 50 µA (93 pC) 50 µA (93 pC)Emittance coupling ratio 0.3% 1%Lifetime ~20h ~20hInjection efficiency (IDs open) 30-40% 15-20%VRF 3.4MV 3.4MVMicro-bunching instability threshold (SB) ~30-35 µA ~15 µABursting 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 scienceElectron bunch length reduced to ~3.5 psPriority on increased single bunch charge over minimum pulse duration (stable!)

THz mode (MIRIAM beamline B22):Above bursting threshold to increase CSR gain in THz regionPriority to extend CSR spectrum towards 100cm-1

Ian MartinIOP PAB Group meeting, DL, (April 2013)

03/10/2012 04/10/2012 05/10/2012

Courtesy G. Cinque

MIRIAM (B22) Spectrum

Ian MartinIOP PAB Group meeting, DL, (April 2013)

Ian MartinIOP 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 MartinIOP PAB Group meeting, DL, (April 2013)

4 Bend Achromat

Magnet arrangement allows 24 additional short straight sectionsNatural 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)

3.35m3.35m

Original DBA

4BA

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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 MartinIOP PAB Group meeting, DL, (April 2013)

5 Bend Achromat

Original DBA

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5BA

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emittance to be maintainedIan Martin

IOP PAB Group meeting, DL, (April 2013)

7 Bend Achromat

Original DBA

0 5 10 15 20X[m]

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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 MartinIOP PAB Group meeting, DL, (April 2013)

MBA Comparison

Existing DBA Modified 4BA 5BA 7BA

Circumference (m) 561.6 561 561.6 561.6

Natural Emittance (pm.rad) 2600 276 155 45.7

Tune Point (Qx / Qy) 27.20 / 13.37 50.76/18.36 53.66/28.87 75.42/52.17

Natural Chromaticity (ξx / ξy) -80.4 / -35.6 -128/ -94 -130/-50 -348 / -119

Momentum compaction 1.66×10-4 1.02×10-4 1.30×10-4 0.80×10-4

Max Quad. Strength (m-2) <2 (1.99) < 7 < 7 < 10

Max Sext. Strength (m-3) <35 (20.0) < 380 < 700 < 326

Emittance with IBS* (pm.rad) - 288 192 103

Length of straight sections# (m) 11.3 / 8.3 9.1 / 6.7 / 3.2 9.5/6.5 8.0 / 5.0

*Intra-Beam Scattering calculated using ELEGANT for 450mA / 900 bunches / 10% coup / 3.3MV#Quadrupole to quadrupole separation

Ian MartinIOP PAB Group meeting, DL, (April 2013)

‘DIAD’ Beamline

Dual Imaging and Diffraction (DIAD) beamline requires high flux in the 4-40keV rangeConsidering 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)

4th RF cavity

Ian MartinIOP 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 MartinIOP PAB Group meeting, DL, (April 2013)

Acknowledgements