• S. Lederer, S. Schreiber
  DESY, Hamburg
• J.H. Han
  Diamond, Oxfordshire
• M. Hänel, F. Stephan
  DESY Zeuthen, Zeuthen
• P.M. Michelato, L. Monaco, C. Pagani, D. Sertore
  INFN/LASA, Segrate (MI)

Caesium telluride photocathodes are used as laser driven electron sources at FLASH and PITZ. FLASH is operated as user facility as well as for accelerator related studies and therefore has a constant and moderate usage of the cathodes. In contrary, PITZ is an injector R&D facility with a stronger usage of cathodes including gradients in the RF-gun of up to 60 MV/m. In the past, one concern of operating RF-guns with Cs2Te cathodes was the degradation of the quantum efficiency in a few weeks at FLASH and a couple of days at PITZ. Improved vacuum conditions and removing contaminants in both accelerators yielded an increased life time of several months. In this contribution we report on routinely performed QE measurements, investigations on the homogeneity of the electron emission, and dark current issues for both facilities.

• J.H. Han
  Diamond, Oxfordshire

To investigate ultrafast dynamics of physical or chemical systems, ultrashort X-rays or electron beams may be used. Compared to X-rays, electron beams are less destructive to material and the scattering cross section is larger, however it is difficult to decrease the electron beam pulse length due to space charge forces. One way of overcoming this difficulty is by means of a photocathode RF gun, which allows the beam energy to be rapidly increased immediately after the electron emission from the photocathode, minimizing therefore the pulse lengthening due to space charge forces. For time-resolved observation of atomic processes electron beams shorter than 100 fs (fwhm) with small divergence are required. In this paper, a conceptual design of a gun system is proposed with beam parameters optimized for relativistic electron diffraction experiments.

• J.H. Han
  Diamond, Oxfordshire

For the successful operation of an X-ray free electron laser the injector must be robust and able to provide a high quality beam. In this paper we present the design of a normal conducting L-band photoinjector which is based on the successful DESY/PITZ gun, but with improved cavity geometry. The result of beam dynamics simulations predicts that a beam with a normalized transverse emittance of less than 0.7 mm mrad at 1 nC can be produced. With an expected repetition rate of at least 1 kHz this gun meets the requirements of the first stage injector for the UK's New Light Source project.

• J.H. Han, H.C. Huang
  Diamond, Oxfordshire

To precisely control the electron beam parameters from a photocathode RF gun, the RF field distribution during real RF operation must be known. During RF operation, the RF field induces local RF heating on the cavity surface. This non-uniform temperature distribution may deform the cavity and affect the output beam parameters. Here, we model a copper RF gun cavity and calculate the temperature distribution and the stress over the cavity surface. Then, the beam parameter change caused by the cavity deformation is simulated.

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

Several new light source projects aim at the production of X-ray photons with high repetition rate (1kHz or above). We present here the results of the start-to-end simulations of a 2.2 GeV superconducting LINAC based on L-band SC Tesla-type RF cavities and the corresponding optimisation of the FEL dynamics at 1 keV photon energy.

• R.P. Walker, R. Bartolini, C. Christou, J.H. Han, J. Kay, I.P.S. Martin, G. Rehm, J. Rowland
  Diamond, Oxfordshire
• D. Angal-Kalinin, M.A. Bowler, J.A. Clarke, D.J. Dunning, B.D. Fell, A.R. Goulden, F. Jackson, S.P. Jamison, J.K. Jones, K.B. Marinov, P.A. McIntosh, J.W. McKenzie, B.L. Militsyn, A.J. Moss, B.D. Muratori, S.M. Pattalwar, M.W. Poole, R.J. Smith, S.L. Smith, N. Thompson, P.H. Williams
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• N. Bliss, G.P. Diakun, M.D. Roper
  STFC/DL, Daresbury, Warrington, Cheshire
• J.L. Collier, C.A. Froud, G.J. Hirst, E. Springate
  STFC/RAL, Chilton, Didcot, Oxon
• J.P. Marangos, J.W.G. Tisch
  Imperial College of Science and Technology, Department of Physics, London
• B.W.J. McNeil
  USTRAT/SUPA, Glasgow
• H.L. Owen
  UMAN, Manchester

The New Light Source (NLS) project was launched in April 2008 by the UK Science and Technology Facilities Council (STFC) to consider the scientific case and develop a conceptual design for a possible next generation light source based on a combination of advanced conventional laser and free-electron laser sources. Following a series of workshops and a period of scientific consultation, the science case was approved in October 2008 and the go-ahead given to continue the project to the design stage. In November the decision was taken that the facility will be based on cw superconducting technology in order to provide the best match to the scientific objectives. In this paper we present the source requirements, both for baseline operation and with possible upgrades, and the current status of the design of the accelerator driver and free-electron laser sources to meet those requirements.