• K.J. Peach, J.H. Cobb, S.L. Sheehy, H. Witte, T. Yokoi
  JAI, Oxford
• M. Aslaninejad, M.J. Easton, J. Pasternak
  Imperial College of Science and Technology, Department of Physics, London
• R.J. Barlow, H.L. Owen, S.C. Tygier
  UMAN, Manchester
• C.D. Beard, P.A. McIntosh, S.M. Pattalwar, S.L. Smith, S.I. Tzenov
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• N. Bliss, T.J. Jones, J. Strachan
  STFC/DL, Daresbury, Warrington, Cheshire
• T.R. Edgecock, J.K. Pozimski
  STFC/RAL, Chilton, Didcot, Oxon
• R.J.L. Fenning, A. Khan
  Brunel University, Middlesex
• I.S.K. Gardner, D.J. Kelliher, S. Machida
  STFC/RAL/ASTeC, Chilton, Didcot, Oxon
• M.A. Hill
  GIROB, Oxford
• C. Johnstone
  Fermilab, Batavia
• B. Jones, B. Vojnovic
  Gray Institute for Radiation Oncology and Biology, Oxford
• R. Seviour
  Cockcroft Institute, Lancaster University, Lancaster

The status of PAMELA (Particle Accelerator for MEdicaL Applications) ' an accelerator for proton and light ion therapy using a non-scaling FFAG (ns-FFAG) accelerator ' is reviewed and discussed.

• A.E. Gustafsson, S. Calatroni, W. Vollenberg
  CERN, Geneva
• R. Seviour
  Cockcroft Institute, Lancaster University, Lancaster

Niobium thin film cavities have shown good and reliable performance for LEP and LHC, although there are limitations to overcome if this technique should be used for new accelerators such as the ILC. New coating techniques like High Power Impulse Magnetron Sputtering (HiPIMS) has shown very promising results and we will report on its possible improvements for Nb thin film cavity performance. Current materials used in accelerator SRF technologies operate at temperatures below 4 K, which require complex cryogenic systems. Researchers have investigated the use of High Temperature Superconductors (HTS) to form RF cavities, with limited success*. We propose a new approach to achieve a high-temperature SRF cavity based on the superconducting 'proximity effect'**. The superconducting proximity effect is the effect through which a superconducting material in close proximity to a non-superconducting material induces a superconducting condensate in the latter. Using this effect we hope to overcome the problems that have prevented the use of HTS for accelerating structures so far. We will report the preliminary studies of magnetron sputtered thin films of Cu on Nb.

* E. J. Minehara et al, Superconductivity 3, p277 (1990)
** R. Seviour et al, Superlattices and Microstructures, 25, p647 (1999)

• A. Zarrebini, M. Ristic
  Imperial College of Science and Technology, London
• K.R. Long
  Imperial College of Science and Technology, Department of Physics, London
• R. Seviour
  Cockcroft Institute, Lancaster University, Lancaster

The ever-growing demand for higher beam energies has dramatically increased the risk of RF breakdown, limiting the maximum achievable accelerating gradient. Field emission is the most frequently encountered RF breakdown where it occurs at regions of locally enhanced electric field. Electrons accelerated across the cavity as they tunnel through the surface in the presence of microscopic defects. Upon Impact, most of the kinetic energy is converted into heat and stress. This can inflict irreversible damage to the surface, creating additional field emission sites. This work aims to investigate, through simulation, the physics involved during both emission and impact of electrons. A newly developed 3D field model of an 805 MHz cavity is generated by COMSOL Multiphysics. Electron tracking is performed using a Matlab based code, calculating the relevant parameters needed by employing fourth Order Runge Kutta integration. By studying such behaviours in 3D, it is possible to identify how the cavity surface can alter the local RF field and lead to breakdown and subsequent damages. The ultimate aim is to introduce new surface standards to ensure better cavity performance.

• Y. Xu
  Lancaster University, Lancaster
• R. Seviour
  Cockcroft Institute, Lancaster University, Lancaster

2D Photonic crystals (PC) with defects can act as standing-wave resonators, which offer benefit of high mode selectivity for building novel RF sources. We introduce our work on designing two-cavity single-beam and multi-beam klystrons using triangular lattice metallic PCs. We present the cold test results of the stub-coupled single-beam structure, which show that at resonance a very low reflection can be obtained, and the waves are well confined. We also present bead-pull measurement results of field strengths in the defect, using modified perturbation equation for small unit dielectric cylinder, which are in very good agreement to numerical results. A 6-beam klystron cavity is designed as a 6-coupled-defect structure with a central stub, which only couples to the in-phase mode at the lowest frequency. Finally, we present a feasibility discussion of using this multi-defect PC structure to construct an integrated klystron-accelerator cavity, along with numerical results showing a peak acceleration field of 22MV/m can be achieved.

• Y.S. Tan
  Lancaster University, Lancaster
• R. Seviour
  Cockcroft Institute, Lancaster University, Lancaster

In this paper we examine the effect of introducing an Electromagnetic metamaterial into a Travelling Wave structure to mediate inverse Cherenkov acceleration. Electromagnetic metamaterials are artificial materials that consist of macroscopic structures that yield an effective permittivity and permeability less than zero. The properties of metamaterials are highly frequency dependent and give rise to very novel dispersion relationships. We show that the introduction of a specifically designed metamaterial into the interaction region gives rise to a novel dispersion curve yielding a unique wave-particle interaction. We demonstrate that this novel wave-particle interaction gives rise energy exchange from wave to beam over an extended interaction regime. We also discuss the benefits and issues that arise from having a metamaterial in a high vacuum high power environment with a specific focus on the issue of loss in metamaterial structures.

• R. Seviour
  Lancaster University, Lancaster

The possibility of achieving higher accelerating gradients at higher frequencies with the reduction of the effect of HOMs, compared to conventional accelerating structures, is increasing interest in the possible use of Photonic Crystals (PC) for accelerator applications. In this paper we analyze how the properties of the lattice of a PC resonator can be engineered to give a specific band structure, and how by tailoring the properties of the lattice specific EM modes can either be confined or moved into the propagation band of the PC. We further go on to discuss the role of disorder in achieving mode confinement and how this can be used to optimize both the Q and the accelerating gradient of a PC based accelerating structure. We also examine the use of high disorder to give rise to Anderson Localization, which gives rise to exponential localization of an EM mode. Discussing the difference between the extended Bloch wave, which extends over the entire PC, and the Anderson localized mode.