M. Liepe

Publications (3)0 Total impact

• Source

  Available from: cern.ch

  Conference Proceeding: Experience with the New Digital RF Control System at the CESR Storage Ring

  M. Liepe, S. Belomestnykh, J. Dobbins, R. Kaplan, C. Strohman, B. Stuhl
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  ABSTRACT: A new digital control system has been developed, providing great flexibility, high computational power and low latency for a wide range of control and data acquisition applications. This system is now installed in the CESR storage ring and stabilizes the vector sum field of two of the superconducting CESR 500 MHz cavities and the output power from the driving klystron. The installed control system includes in-house developed digital and RF hardware, very fast feedback and feedforward control, a state machine for automatic start-up and trip recovery, cw and pulsed mode operation, fast quench detection, and cavity frequency control. Several months of continuous operation have proven high reliability of the system. The achieved field stability surpasses requirements.
  Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
• Source

  Available from: jacow.org

  Conference Proceeding: Pushing the Limits: RF Field Control at High Loaded Q

  M. Liepe, S. Belomestnykh, J. Dobbins, R. Kaplan, C. Strohman, B. Stuhl, C. Hovater, T. Plawski
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  ABSTRACT: The superconducting cavities in an Energy-Recovery-Linac will be operated with a high loaded Q of several 10⁷, possible up to 10⁸. Not only has no prior control system ever stabilized the RF field in an elliptical linac cavity with such high loaded Q, but also highest field stability in amplitude and phase is required at this high loaded Q. Because of a resulting bandwidth of the cavity of only a few Hz, this presents a significant challenge: the field in the cavity is extremely sensitive to any perturbation of the cavity resonance frequency due to microphonics and Lorentz force detuning. To prove that the RF field in a high loaded Q cavity can be stabilized, and that Cornell’s newly developed digital control system is able to achieve this, the system was connected to a high loaded Q cavity at the JLab IR-FEL. Excellent cw field stability - about 10^{− 4}rms in relative amplitude and 0.02 deg rms in phase - was achieved at a loaded Q of 2.1 · 10⁷and 1.2 · 10⁸, setting a new record in high loaded Q operation of an elliptical linac cavity. Piezo tuner based cavity frequency control proved to be very effective in keeping the cavity on resonance and allowed reliably to ramp up to high gradients in less than 1 second.
  Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
• Source

  Available from: triumf.ca

  Article: CW RF systems of the Cornell ERL injector

  S Belomestnykh, Z Conway, J Dobbins, R Kaplan, M Liepe, P Quigley, J Reilly, J Sikora, C Strohman, V Veshcherevich, Classe
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  ABSTRACT: Two high power 1300 MHz RF systems have been developed for the Cornell University ERL Injector. The first system, based on a 16 kWCW IOT transmitter, is to provide RF power to a buncher cavity. The second system employs five 120 kWCW klystrons to feed 2-cell superconducting cavities of the injector cryomodule. The sixth, spare klystron is used to power a deflecting cavity in a pulsed mode for beam diagnostics. A digital LLRF control stem was designed and implemented for precise regulation of the cavities' field amplitudes and phases. All components of these systems have been recently installed and commissioned. The first operational experience with the systems is discussed.