• I.P.S. Martin
  Diamond, Oxfordshire
• R. Bartolini, I.P.S. Martin
  JAI, Oxford
• D.J. Dunning, N. Thompson
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

The New Light Source project aims to construct a suite of seeded free-electron lasers driven by a 2.25GeV cw super conducting linac. As part of the upgrade path, a number of options are being considered for generating ultra short (<1fs) soft x-ray pulses, with low-charge 'single-spike' operation and bunch slicing like approaches of particular interest, including as a possible extension to echo-enhanced harmonic generation. In this paper we present the status of this work, including recent results from fully start to end simulations.

• R. Bartolini, C. Christou, J.H. Han, I.P.S. Martin, J. Rowland
  Diamond, Oxfordshire
• D. Angal-Kalinin, D.J. Dunning, F. Jackson, B.D. Muratori, N. Thompson, P.H. Williams
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

We present the progress with the design of the 2.25 GeV superconducting linac for the NLS project. We discuss the performance achieved, the optimisation strategies, the relevance of microbunching instability and the analysis of the effect of various jitter sources

• C. Christou, J.A. Dobbing, R.T. Fielder, I.P.S. Martin, S.J. Singleton
  Diamond, Oxfordshire

Diamond Light Source has delivered beam for users exclusively in top-up mode since the end of October 2008. In this mode, a small number of single bunches are injected into specific buckets of the storage ring every ten minutes in order to maintain a constant beam current and fill pattern. During top-up the storage ring current is held within a window of approximately 1.5mA around the target current, generally 250mA, for a variety of fill patterns, including a two-thirds storage ring fill and a hybrid fill in which an intense single bunch is added to the normal fill pattern. Top-up has run continuously for several days on many occasions, with injection efficiency into the storage ring of typically 60%-95% even with 10 in-vacuum insertion device in operation with a permitted minimum gap of 5 mm. The effect of insertion devices, pulsed magnet stability and storage ring beam optics on top-up reliability and performance is examined, and the development of tools for the control of top-up and storage ring fill is detailed.

• I.P.S. Martin, G. Rehm, J. Rowland, C.A. Thomas
  Diamond, Oxfordshire
• R. Bartolini, I.P.S. Martin
  JAI, Oxford

The Diamond storage ring has been operated in low alpha mode providing short-pulse radiation for pump-probe experiments and coherent radiation for THz/IR measurements. Two lattices have been implemented, with both capable of providing a variable alpha in the range ±2x10^-5, down to minimum values well below 1x10^-6. The second lattice additionally provides a low emittance of 4nm.rad, compared to 35nm.rad for the first lattice. An overview of operation in low alpha mode is given, along with first measurements of coherent emission at long wavelengths under a variety of conditions.

• C.A. Thomas, G. Rehm
  Diamond, Oxfordshire
• I.P.S. Martin
  JAI, Oxford

Electron bunch profile and length measurement from large bandwidth synchrotron radiation with a streak camera can be strongly limited by the chirp introduced by the length of material present in the input refractive optics of streak cameras. Elimination of the chirp can be done either by filtering the bandwidth of the synchrotron radiation pulses, by measuring time resolved spectra with the streak camera, or by replacing the front optics lenses by focussing mirrors. The first solution reduces the power available, thus limiting measurements to minimum bunch current that can be too high to assess the 'zero' current bunch length. The second elegant solution allows measurement of the bunch length with the whole bandwidth and available power but with loss of the second sweep axis in the camera, so that no beam dynamics can be observed. In order to prevent any pulse chirp, keep all the available power and capability of beam dynamics observation, we designed a new input optics exclusively with mirrors. We present here our design and the results of the system with our streak camera, measuring 2ps bunch in the new Diamond low-alpha lattice.

• P.H. Williams, D.J. Dunning, N. Thompson
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• D. Angal-Kalinin, J.K. Jones, P.H. Williams
  Cockcroft Institute, Warrington, Cheshire
• R. Bartolini, I.P.S. Martin
  JAI, Oxford
• J. Rowland
  Diamond, Oxfordshire

We present progress in the design of the recirculating linac option for the UK New Light Source. Improvements in all accelerator sections have been made such that the output meets the required specifications to drive the seeded NLS FELs. Full start-to-end simulations and tolerance studies are presented together with a comparison to the baseline, single pass linac design.

• D. Angal-Kalinin, P.H. Williams
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• D. Angal-Kalinin, F. Jackson, S.P. Jamison, J.K. Jones, B.D. Muratori, N. Thompson
  Cockcroft Institute, Warrington, Cheshire
• R. Bartolini, I.P.S. Martin
  JAI, Oxford

The design of free electron laser (FEL) driver needs careful beam transport design to pass very short bunches through the switchyard/spreader to switch the beam to different FEL lines. The spreader design which allows flexibility in operation has been adapted following the LBNL design*. In order to measure the slice properties of the bunches two beam diagnostics lines are proposed, a straight one for beam commissioning purposes and a branch of the spreader similar to the FEL lines to measure the adverse effects that may arise due to passing the short bunches through the kicker and septum magnets. As a part of machine protection, post linac collimation system collimates the halo particles in transverse and energy planes. The design of the collimation, beam spreader and beam diagnostics lines is discussed.

* Zholents A.A. et al, CBP Tech Note 401, 2009

• I.P.S. Martin, G. Rehm, J. Rowland, C.A. Thomas
  Diamond, Oxfordshire
• R. Bartolini, I.P.S. Martin
  JAI, Oxford

The Diamond storage ring has been operated in low alpha mode providing short-pulse radiation for pump-probe experiments and coherent radiation for THz/IR measurements. Two lattices have been implemented, with both capable of providing a variable alpha in the range ±2x10^-5, down to minimum values well below 1x10^-6. The second lattice additionally provides a low emittance of 4nm.rad, compared to 35nm.rad for the first lattice. An overview of operation in low alpha mode is given, along with first measurements of coherent emission at long wavelengths under a variety of conditions.

• R. Bartolini, G. Rehm, J. Rowland
  Diamond, Oxfordshire
• P. Kuske
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
• I.P.S. Martin
  JAI, Oxford
• F. Schmidt
  CERN, Geneva

The correct implementation of the nonlinear ring model is crucial to achieve the top performance of a synchrotron light source. Several dynamics quantities can be used to compare the real machine with the model and eventually to correct the accelerator. Most of these methods are based on the analysis of turn-by-turn data of excited betatron oscillations. We present the experimental results of the campaign of measurements carried out at the Diamond. A combination of Frequency Map Analysis and resonant driving terms measurements has allowed a precise calibration of the nonlinear model capable of reproducing and then correcting the nonlinear beam dynamics in the storage ring.

• B. Singh, R.T. Fielder, J. Rowland
  Diamond, Oxfordshire
• R. Bartolini, I.P.S. Martin
  JAI, Oxford

Diamond operates with 10 in-vacuum insertion devices at 5 mm gap, two Apple-II, two superconducting and two normal conducting wigglers. We report here the correction of the linear optics of wigglers and measurements of nonlinear effects such as dynamic aperture and frequency maps and their impacts on injection efficiency, lifetime and loss distribution in operation of the storage ring.