• D. Schulte, A. Andersson, S. Bettoni, R. Corsini, A. Dubrovskiy, A. Gerbershagen, J.B. Jeanneret, G. Morpurgo, G. Sterbini, F. Stulle, R. Tomás
  CERN, Geneva
• A. Aksoy
  Ankara University, Faculty of Engineering, Tandogan, Ankara
• V.R. Arsov, M.M. Dehler
  PSI, Villigen
• P. Burrows, C. Perry
  JAI, Oxford
• F. Marcellini
  INFN/LNF, Frascati (Roma)

In CLIC very tight tolerances exist for the phase and amplitude stability of the main and drive beam. In this paper we present the status of the CLIC beam phase and amplitude stabilisation concept. We specify the resulting tolerances for the beam and technical equipment and compare to first measurements.

• W. Höfle, M. Hernandez Flano, J. Lollierou, D. Valuch
  CERN, Geneva
• S. Chel, M. Desmons, G. Devanz, O. Piquet
  CEA, Gif-sur-Yvette
• R. Paparella, P. Pierini
  INFN/LASA, Segrate (MI)

In the framework of the preparatory phase for the luminosity upgrade of the LHC (SLHC-PP ) it is foreseen to characterize two superconducting RF cavities and demonstrate compliance of the required SPL field stability in amplitude and phase using a prototype LLRF system. We report on the preparation for testing of two super-conducting low-beta cavities at 50 Hz pulse repetition rate including the setting-up of the low level RF control system to evaluate the performance of the piezo-tuning system and cavity field stability in amplitude and phase. Results from tests with 50 Hz pulse repetition rate are presented. Simulations of the RF system are used to predict the necessary specifications for power and bandwidth to control the cavity field and derive specifications for the RF system and its control.

This project has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under the Grant Agreement no 212114

• L. Laurent, V.A. Dolgashev, C.D. Nantista, S.G. Tantawi
  SLAC, Menlo Park, California
• M. Aicheler, S.T. Heikkinen, W. Wuensch
  CERN, Geneva
• Y. Higashi
  KEK, Ibaraki

Cavity pulsed heating experiments have been conducted at SLAC National Accelerator Laboratory in collaboration with CERN and KEK. These experiments were designed to gain a better understanding on the impact of high power pulsed magnetic fields on copper and copper alloys. The cavity is a one port hemispherical cavity that operates in the TE013-like mode at 11.424 GHz. The test samples are mounted onto the endcap of the cavity. By using the TE013 mode, pulsed heating information can be analyzed that is based only on the impact of the peak magnetic field which is much bigger in value on the test sample than on any other place in the cavity. This work has shown that pulsed heating surface damage on copper and copper alloys is dependent on processing time, pulsed heating temperature, material hardness, and crystallographic orientation and that initial stresses occur along grain boundaries which can be followed by pitting or by transgranular microfractures that propagate and terminate on grain boundaries. The level of pulsed heating surface damage was found to be less on the smaller grain samples. This is likely due to grain boundaries limiting the propagation of fatigue cracks.

• P. Varghese, B. Barnes, J. Branlard, B. Chase, E. Cullerton, P.W. Joireman, V. Tupikov
  Fermilab, Batavia

A LLRF control and data acquisition system for the 8-cavity Cryo-Module 1 at the ILCTA has been implemented using three , 33-channel MFC boards in a VXI mainframe. One card each is dedicated for the cavity probes for vector control , forward power and reverse power measurements. The system is scalable to 24 cavities or more with the commissioning of Cryo-Modules 2 and 3 without additional hardware. The signal processing and vector control of the cavities is implemented in a FPGA and a high speed data acquisition system with upto 100 channels stores data in external SDRAM memory. The system supports both pulsed and CW modes with a pulse rate of 5Hz. Acquired data is transferred between pulses to auxiliary systems such as the piezo controller through the slot0 controller. The design of the system is described and the performance of the vector control system is evaluated.

• T. E. Plawski, C. Hovater
  JLAB, Newport News, Virginia

A digital low level radio frequency (RF) system typically incorporates either a heterodyne or direct sampling technique, followed by fast ADCs, then an FPGA, and finally a transmitting DAC. This universal platform opens up the possibilities for a variety of control algorithm implementations. The foremost concern for an RF control system is cavity field stability, and to meet the required quality of regulation, the chosen control system needs to have sufficient feedback gain. In this paper we will investigate the effectiveness of the regulation for three basic control system algorithms: I&Q (In-phase and Quadrature), Amplitude & Phase and digital SEL (Self Exciting Loop) along with the example of the Jefferson Lab 12 GeV cavity field control system.

• M. Popovic, A. Moretti
  Fermilab, Batavia
• A. Dudas, R.P. Johnson, M.L. Neubauer, R. Sah
  Muons, Inc, Batavia

Magnetrons are the lowest cost microwave source in dollars/kW, and they have the highest efficiency (typically greater than 85%). However, the frequency stability and phase stability of magnetrons are not adequate when used as power sources for accelerators. Novel variable frequency cavity techniques have been developed to phase and frequency lock the magnetrons, allowing their use for either individual cavities, or cavity strings. Ferrite or YIG (Yttrium Iron Garnet) materials are placed in the regions of high magnetic field of radial-vaned, π−mode structures of a selected ordinary magnetron. A variable external magnetic field that is orthogonal to the magnetic RF field of the magnetron surrounds the magnetron to vary the permeability of the ferrite or YIG material. Measurements of a prototype magnetron will be described.