• 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.

• C. Hovater, T.L. Allison, R. Bachimanchi, G.E. Lahti, J. Musson, T. E. Plawski, C. Seaton, D.J. Seidman
  JLAB, Newport News, Virginia

To support the CEBAF energy upgrade from 6 GeV to 12 GeV, the RF control system is being modernized to control the high gradient high QL superconducting cavities. The new system incorporates a heterodyne transceiver along with I&Q sampling to measure and control magnitude and phase. A low-cost Altera FPGA is used to digitally implement the cavity control algorithms. One of the features of the system is a digital self excited loop to track the cavity over large Lorentz detuning (800 Hz) during turn on. The system has successfully completed preliminary development and is now moving into the production stage of the project. This paper discusses the design, modeling, testing and production of the new RF control system and associated peripheral systems (cavity interlocks, and resonance control).