• C.A. Thomas, G. Rehm
  Diamond, Oxfordshire
• S.I. Bajlekov
  University of Oxford, Clarendon Laboratory, Oxford
• R. Bartolini, N. Delerue
  JAI, Oxford

Single shot emittance measurement is essential to assess the performance of new generation light sources such as linac based X-ray FELs or laser plasma wakefield accelerators. To this aim, we have developed a single shot emittance measurement using at least 3 screens inserted in the beam at the same time, measuring the beam size at different positions in a drift space in one shot. We present here test measurements performed at Diamond in the transfer line from the Booster to the Storage Ring, using thin OTR and also YAG screens. We also compare these measurements with results from the more conventional quadrupole scan method and also measurements using an OTR screen and an assembly of two cameras imaging the beam size and the beam divergence at a point near the waist of the beam. The validity and limits of the new method are discussed in the paper.

• 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.

• C. Bloomer, G. Rehm, C.A. Thomas
  Diamond, Oxfordshire

We present our observations of the medium term and long term stability of the photon beams at Diamond Light Source. Drift of the Electron Beam Position Monitors results in real X-ray beam movements, observed by both Front End X-ray Beam Position Monitors and beamline scintillator screens on some beamlines. We discuss how we are using these diagnostics tools to measure and characterise the drift. Medium term movements related to top-up cycles are seen, believed to be caused by changes to single bunch charge, and the long term drift of the electron beam position over several days and weeks is examined. A slow feedback system using X-ray Beam Position Monitors has been shown to successfully correct this drift. The results of these trials are presented.

• 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.