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Ratti, A.

Paper Title Page
TPPE022 First Results on the Path Towards a Microwave-Assisted H- Ion Source 1784
 
  • R. Keller, P.A. Luft, M. T. Monroy, A. Ratti, M.J. Regis, D. L. Syversrud, J.G. Wallig
    LBNL, Berkeley, California
  • D.E. Anderson, R.F. Welton
    ORNL, Oak Ridge, Tennessee
  
  Funding: This work supported by Office of Basic Energy Sciences, U.S. Department of Energy under Contract No. DE-AC03-76SF00098.

A novel concept for creating intense beams of negative hydrogen ion beams is presented. In this approach, an ECR ion source operating at 2.45 GHz frequency is utilized as a primary plasma generator and coupled to an SNS-type multi-cusp H- ion source. The secondary source is driven by chopped dc power avoiding the use of filaments or of an internal rf antenna. The development of the new ion source is aimed at the future beam-power goal of 3 MW for the Spallation Neutron Source (SNS) that will be pursued after the start of SNS operations, but application to other proton driver accelerators that include an accumulator ring is feasible as well. The first two phases of this development effort have been successfully completed: assembly of a test stand and verification of the performance of an rf-driven SNS ion-source prototype; and extraction of electrons with more than 350 mA current from a 2.45-GHz ECR ion source obtained on loan from Argonne National Laboratory. The next goal is the demonstration of actual H- ion production by this novel, hybrid ion source. This paper describes the source principle and design in detail and reports on the current status of the development work.

 
WPAT057 Overview of the Spallation Neutron Source Linac Low-Level RF Control System 3396
 
  • M. Champion, M.T. Crofford, K.-U. Kasemir, H. Ma, M.F. Piller
    ORNL, Oak Ridge, Tennessee
  • L.R. Doolittle, A. Ratti
    LBNL, Berkeley, California
  
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.

The design and production of the Spallation Neutron Source Linac Low-Level RF control system is complete, and installation will be finished in Spring 2005. The warm linac beam commissioning run in Fall 2004 was the most extensive test to date of the LLRF control system, with fourteen (of an eventual 96) systems operating simultaneously. In this paper we present an overview of the LLRF control system, the experience in designing, building and installing the system, and operational results.

 
WPAT060 SNS Low-Level RF Control System: Design and Performance 3479
 
  • H. Ma, M. Champion, M.T. Crofford, K.-U. Kasemir, M.F. Piller
    ORNL, Oak Ridge, Tennessee
  • L.R. Doolittle, A. Ratti
    LBNL, Berkeley, California
  
  Funding: ORNL managed by UT-Battelle for US DOE.

A full digital Low-Level RF controller has been developed for SNS LINAC. Its design is a good example of a modern digital implementation of the classic control theory. The digital hardware for all the control and DSP functionalities, including the final vector modulation, is implemented on a single high-density FPGA. Two models for the digital hardware have been written in VHDL and Verilog respectively, based on a very low latency control algorithm, and both have been being used for supporting the testing and commissioning the LINAC to the date. During the commissioning, the flexibility and ability for precise controls that only digital design on a larger FPGA can offer has proved to be a necessity for meeting the great challenge of a high-power pulsed SCL.