A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z  

Ma, H.

Paper Title Page
MOPAS078 Digital RF Control for Spallation Neutron Source Accumulator Ring 611
 
  • H. Ma, M. S. Champion, M. T. Crofford, T. W. Hardek, K.-U. Kasemir, M. F. Piller, Y. Zhang
    ORNL, Oak Ridge, Tennessee
 
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy.

The proposed upgrade plan for RF control of the Spallation Neutron Source (SNS) accumulator ring requires that the new digital field control module (FCM) support both the conventional narrow-band feed forward control and a new beam-based feed forward control. Both are necessary for compensating the heavy beam loading in SNS ring. The ring FCM also has the integrated control and monitoring features for the cavity bias, cavity resonance, and tetrode grid boost. A user-friendly Epics GUI for all these FCM functionalities is also a part of the requirement. The ring FCM under development is being implemented on the hardware of the proven FCM of SNS Linac. Both the controller architecture and the design code of the digital hardware for the Linac system will be largely reused in the ring system.

 
WEPMS080 SRF Cavity Transient Beam Loading Detection - Simulation and Measurement 2517
 
  • Y. Zhang, I. E. Campisi, C. Deibele, J. Galambos, S. Henderson, Y. W. Kang, H. Ma, J. L. Wilson
    ORNL, Oak Ridge, Tennessee
 
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy.

Beam phase measurement based on detection of transient beam loading signal in a Superconducting (SC) cavity is utilized to setup the cavity synchronous phase. It has the potential to become a fast tune-up technique for a high intensity SC electron linac, as cavity phase could be determined precisely with only a few beam pulses. The paper introduces a transient detector study in the Spallation Neutron Source (SNS) proton linac, and discusses one of the major challenges - stochastic noise in the cavity RF system, which deteriorates the precision and increases the time needed for phase measurement with this technique. We analyze the influence of RF noise to the phase measurement in a simulation study with a beam-cavity model. Beam signal measurement with the cavity Low Level RF (LLRF) system and the initial experiment of prototype detectors are briefly introduced.

 
WEPMS081 Simulation and Initial Test Result of the SNS Ring RF System 2520
 
  • Y. Zhang, M. S. Champion, P. Chu, S. M. Cousineau, V. V. Danilov, T. W. Hardek, J. A. Holmes, H. Ma, M. F. Piller, M. A. Plum
    ORNL, Oak Ridge, Tennessee
 
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy

A simulation code has been developed for the study of the Spallation Neutron Source (SNS) ring RF control. The code uses the time-domain solvers to compute beam-cavity interactions, and FFT methods to simulate time responses of the linear RF system. The important ingredients of the system are considered in the simulation model, which include the beam loading, dynamic cavity detuning, circuit bandwidth, loop delay, proportional-integral (P-I) controller for feedback and adaptive feed forward, stochastic noise, with-in-turn RF parameter change, beam current fluctuation and beam bunch leakage, etc. The beam loss in the accumulation ring goes up as the beam power increases, and thus a precise control of bunching voltage phase and amplitude is required to limit beam loss. This simulation tool will help the development a correct RF control and to achieve the goal of minimizing the beam loss.

 
MOPAS079 Spallation Neutron Source (SNS) High Pulse Repetition Rate Considerations 614
 
  • M. P. McCarthy, D. E. Anderson, I. E. Campisi, F. Casagrande, R. I. Cutler, G. W. Dodson, J. Galambos, D. P. Gurd, Y. W. Kang, K.-U. Kasemir, S.-H. Kim, H. Ma, B. W. Riemer, J. P. Schubert, M. P. Stockli
    ORNL, Oak Ridge, Tennessee
 
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy.

Increasing the pulse repetition rate (PRR) of the SNS Linac to its designed maximum of 60 Hz to provide 1.4 MW of beam on target is in progress. Operation above 60 Hz in the future to provide beam to a second target is also being considered. Increasing the PRR to 80 Hz would allow the additional pulses to be diverted to a second target. This paper discusses the impact of increasing the PRR on the SNS infrastructure including Radio Frequency (RF) systems and structures, the ion source, cryogenics, controls and the target.

 
WEPMS072 Status and Performance of the Spallation Neutron Source Superconducting Linac 2502
 
  • I. E. Campisi, S. Assadi, F. Casagrande, M. S. Champion, M. T. Crofford, G. W. Dodson, J. Galambos, M. Giannella, S. Henderson, M. P. Howell, Y. W. Kang, K.-U. Kasemir, S.-H. Kim, Z. Kursun, P. Ladd, H. Ma, D. Stout, W. H. Strong, Y. Zhang
    ORNL, Oak Ridge, Tennessee
 
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy

The Superconducting Linac at SNS has been operating with beam for almost two years. As the first operational pulsed superconducting linac, many of the aspect of its performance were unknown and unpredictable. A lot of experience has been gathered during the commissioning of its components, during the beam turn on and during operation at increasingly higher beam power. Some cryomodules have been cold for well over two years and have been extensively tested. The operation has been consistently conducted at 4.4 K and 10 and 15 pulses per second, with some cryomodules tested at 30 and 60 pps and some tests performed at 2 K. Careful balance between safe operational limits and the study of conditions, parameters and components that create physical limits has been achieved. This paper presents the experience and the performance of the superconducting cavities and of the associated systems with and without beam.

 
FROAC01 The Spallation Neutron Source Accumulator Ring RF System 3795
 
  • T. W. Hardek, M. S. Champion, M. T. Crofford, H. Ma, M. F. Piller
    ORNL, Oak Ridge, Tennessee
  • K. Smith, A. Zaltsman
    BNL, Upton, Long Island, New York
 
  Funding: SNS is managed by UT-Batelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy.

The Spallation Neutron Source (SNS) accumulator ring is a fixed-frequency proton storage ring located at the output of the SNS Linear Accelerator (Linac). Its purpose is to convert 1 millisecond H- beam pulses from the SNS Linac into high-intensity 695 nanosecond pulses of protons for delivery to the neutron target. The RF bunching system controls longitudinal beam distribution during the accumulation process and maintains a 250+ nanosecond gap required for beam extraction. The RF system consists of three stations which operate at a beam revolution frequency of 1.05 MHz while a fourth station provides a second harmonic component at 2.1 MHz. The beam pulse at extraction consists of 1.6·1014 protons representing a peak beam current of 52 amperes. The system utilizes four 600kW tetrodes to provide the RF current necessary to produce the 40kV peak-bunching voltage and to control phase and amplitude at this high beam current. In this paper we review the design concepts incorporated into this heavily beam-loaded RF system and discuss its commissioning status.

 
slides icon Slides