• R.J. Nousiainen, K. Osterberg
  HIP, University of Helsinki
• G. Riddone
  CERN, Geneva

To fulfill the mechanical requirements set by the luminosity goals of the CLIC collider, currently under study, the 2-m two-beam modules, the shortest repetitive elements in the main linac, have to be controlled at micrometer level. At the same time these modules are exposed to variable high power dissipation while the accelerator is ramped up to nominal power as well as when the mode of CLIC operation is varied. This will result into inevitable temperature excursions driving mechanical distortions in and between different module components. A FEM model is essential to estimate and simulate the fundamental thermo-mechanical behavior of the CLIC two-beam module to facilitate its design and development. Firstly, the fundamental thermal environment is created for different RF components of the module. Secondly, the first thermal and structural contacts for adjacent components as well as idealized kinematic coupling for the main module components are introduced. Finally, the thermal and structural results for the studied module configuration are presented showing the fundamental thermo-mechanical effects of primary CLIC collider operation modes.

• S. Verdú-Andrés, U. Amaldi, R. Bonomi, A. Degiovanni, M. Garlasché
  TERA, Novara
• A. Garonna
  EPFL, Lausanne
• C. Mellace, P. Pearce
  A.D.A.M. S.A., Geneva
• S. Verdú-Andrés
  IFIC, Valencia
• R. Wegner
  CERN, Geneva

Proton and carbon ion beams present advantageous depth-dose distributions with respect to X-rays. Carbon ions allow a better control of "radioresistant" tumours due to their higher biological response. For deep-seated tumours proton and carbon ion beams of some nA and energies of about 200 MeV and 400 MeV/u respectively are needed. For these applications TERA proposed the "cyclinac": a high-frequency linac which boosts the hadrons accelerated by a cyclotron. The dimensions of the complex can be reduced if higher accelerating gradients are achieved in the linac. To test the maximum achievable fields, a 3 GHz cavity has been built by TERA. The 19 mm-long cell is foreseen to be excited at 200 Hz by 3 us RF pulses and should reach a 40 MV/m accelerating gradient, which corresponds to a peak surface electric field Es of 260 MV/m. In a first high-power test performed at CTF3 the cell was operated at 50 Hz with a maximum peak power of 1 MW. The maximum Es achieved was above 350 MV/m. The breakdown rate at these field values was around 10^-1 bpp/m. The maximum value of the modified Poynting vector is close to the best values achieved by high gradient structures at 12 and 30 GHz.