• M. E. Angoletta, A. Blas, A.C. Butterworth, A. Findlay, P.M. Leinonen, J.C. Molendijk, F. Pedersen, J. Sanchez-Quesada, M. Schokker
  CERN, Geneva

In 2008 a project was started to renovate the CERN's PS Booster (PSB) low-level RF (LLRF). Its aim is to equip all four PSB rings with modern LLRF systems by 2013 at the latest. Required capabilities for the new LLRF include frequency program, beam phase, radial and synchronization loops. The new LLRF will control the signals feeding the three RF cavities present in each ring; it will also shape the beam in a dual harmonic mode, operate a bunch splitting and create a longitudinal blow-up. The main benefits of this new LLRF are its full remote and cycle-to-cycle controllability, built-in observation capability and flexibility. The overall aim is to improve the robustness, maintainability and reliability of the PSB operation and to make it compatible with the injection from the future LINAC4. The chosen technology is an evolution of that successfully deployed in CERN's ion accumulator ring LEIR and it is based upon modular VME 64X hardware and extensive digital signal processing. This paper outlines the main characteristics of the software and hardware building blocks. Promising initial beam tests are shown and hints are included on the main milestones and future work.

• T. Mastorides, J.D. Fox, C.H. Rivetta, D. Van Winkle
  SLAC, Menlo Park, California
• P. Baudrenghien, A.C. Butterworth, J.C. Molendijk
  CERN, Geneva

Radio Frequency (RF) accelerating system noise and non-idealities can have detrimental impact on the LHC performance through longitudinal motion and longitudinal emittance growth. A theoretical formalism has been developed to relate the beam and RF loop dynamics with the bunch length growth [1]. Measurements were conducted at LHC to validate the formalism, determine the performance limiting RF components, and provide the foundation for beam diffusion estimates for higher energies and intensities. A brief summary of these results is presented in this work.

[1] T. Mastorides et. al., "RF system models for the LHC with Application to
Longitudinal Dynamics", prepared for submission to Physical Review ST-AB.

• D. Van Winkle, J.D. Fox, T. Mastorides, C.H. Rivetta
  SLAC, Menlo Park, California
• P. Baudrenghien, A.C. Butterworth, J.C. Molendijk
  CERN, Geneva

The LHC Low Level RF system (LLRF) is a complex multi-loop system used to regulate the superconductive cavity gap voltage as well as to reduce the impedance presented by RF stations to the beam. The RF system can have a profound impact on the stability of the beam; a mis-configured RF system has the potential of causing longitudinal instabilities, beam diffusion and beam loss. To configure the RF station for operation, a set of parameters in the LLRF multi-loop system have to be defined. Initial system commissioning as well as ongoing operation requires a consistent method of computer based remote measurement and model-based design of each RF station feedback system. This paper describes the suite of Matlab tools used for configuring the LHC RF system during the start up in Nov2009-Feb2010. We present a brief overview of the tool, examples of commissioning results, and basics of the model-based design algorithms. This work complements our previous presentation [1], where the algorithms and methodology followed in the tools were described.

[1] D. Van Winkle et. al. 'Feedback Configuration Tools for LHC Low Level RF System,' PAC'09, Vancouver, Canada, May 2009, THZCH03, p. 249 (2009); http://www. JACoW.org.