• D. Longuevergne, S. Blivet, G. Martinet, G. Olry, H. Saugnac
  IPN, Orsay

SPIRAL2 aims at building a multi-purpose facility dedicated to nuclear physics studies, including the production of rich-neutrons isotopes. The multi-beam linear accelerator is composed of superconducting accelerating modules and warm focusing magnets. IPN Orsay is in charge of the high energy accelerating modules, each hosting two superconducting (β = 0.12) quarter-wave resonators operating at an accelerating field of 6.5 MV/m at 88 MHz. The static and dynamic frequency tuning is achieved by the insertion and motion of a niobium plunger into the magnetic field area. The efficiency of the tuning (1 kHz/mm) has been validated during the tests of the cryomodule. In this paper we discuss the impact of such a tuning system, based on experimental results on Spiral2 cavities, on the different aspects: maximum accelerating field, Qo slopes, quench, multipacting and microphonics.

• R. Paparella, A. Bosotti, C. Pagani, N. Panzeri
  INFN/LASA, Segrate (MI)
• C. Albrecht, R. Lange, L. Lilje
  DESY, Hamburg
• J. Knobloch, O. Kugeler, A. Neumann
  BESSY GmbH, Berlin

Cavity tuners are needed to precisely tune the narrow-band resonant frequency of superconducting cavities. The Blade Tuner presented is installed coaxially to the cavity and changes the resonator frequency by varying its length. Piezoceramic actuators add dynamic tuning capabilities, allowing fast compensation of main dynamic instabilities as Lorentz Forces, under pulsed operations, and microphonic noise. A prototype piezo Blade Tuner has been assembled on a TESLA cavity and extensively cold tested inside the horizontal cryostats CHECHIA (DESY) and HoBiCaT (BESSY). Then, as suggested by results, a few minor modifications have been implemented thus achieving the current Blade Tuner design. The introduction of thicker blades re-distributed along the circumference allows to increase its stiffness and fulfill European and American pressure vessel codes, while ensuring requested performances and cost. The paper will present the successful characterization tests performed on the prototype, the extensive mechanical analyses made to validate the final model and the results from qualification tests of first revised Blade Tuner produced, to be installed in the second module of ILCTA at FNAL.

• M. Schuh
  CERN, Geneva
• K.-U. Kühnel, C.P. Welsch
  MPI-K, Heidelberg
• M. Schuh
  GSI, Darmstadt

Rebunching cavities are today routinely used for matching a beam of charged particles between different accelerator structures, and thus optimizing the overall transmission and beam quality. At low resonance frequencies, unnecessary large dimensions of these cavities can be avoided by using spiral-loaded cavities. The optimization of these structures is a complicated process in which a wide range of different parameters have to be modified essentially in parallel. In this contribution, we investigate in detail the characteristics of a model structure with the 3D code OPERA/SOPRANO. This includes the optimization of the structure in terms of the spiral geometry for a given resonance frequency, the investigation of power losses on the inner surfaces, and the possibility of cavity tuning by means of a tuning cylinder.