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Kwon, S.

Paper Title Page
WEPMS022 Gain Scheduled Neural Network Tuned PI Feedback Control System for the LANSCE Accelerator 2379
  • S. Kwon, J. Davis, M. T. Lynch, M. S. Prokop, S. Ruggles, P. A. Torrez
    LANL, Los Alamos, New Mexico
  The current LANSCE LLRF system is an analog proportional/integral (PI) feedback control system that achieves amplitude and phase errors within 1% and 1 degree. The feedback system receives the cavity amplitude and phase, and the crosstalk between the amplitude and phase is significant. In this note, we propose an In-phase (I) and Quadrature (Q) based feedback control system which easily decouples the crosstalk of I and Q channels. For LANSCE-R, the current RF amplifier chain has to be preserved, so the controller output I/Q is transferred back to amplitude/phase values which drive the RF amplifier chain. The resultant feedback system reduces transient peaks of the RF and hence reduces the degradation of the RF amplifier chain. Self-tuning is performed every clock cycle. This feature of the feedback controller can reduce the beam loading transient drastically. The proposed control system is implemented with the Altera Stratix II FPGA. The proposed control system will first be tested on the low power test-stand to determine the robustness of the algorithm and will then be tested on a LANSCE Drift Tube Linac (DTL) tank.  
WEPMS025 LANSCE-R Low Level RF Control System 2388
  • M. S. Prokop, S. Kwon, S. Ruggles, P. A. Torrez
    LANL, Los Alamos, New Mexico
  The Los Alamos Neutron Science Center proton accelerator is scheduled for refurbishment. A new low level RF(LLRF) system is part of the refurbishment plan since the existing LLRF system is analog-based and requires significant setup and maintenance time. Both field and resonance control aspects of the current system do not have the flexibility to meet future performance requirements. The LANSCE accelerator provides both H+ and H- beams and due to the various user requirements there are a number of different beam pulse types varying in timing and current. In order to meet user needs, LANSCE must simultaneously transport both H+ and H- in the accelerator. These requirements have motivated the development of a new LLRF system based on software defined radio technology. The new system will include field control using feedback and adaptive feed forward techniques, an upgraded resonance controller with frequency agility to improve startup and fault recovery times and a high power amplifier pre-compensation controller for improved cavity fill times and amplifier efficiency. Among the challenges with implementing the new system are interfacing with existing subsystems of the accelerator.  
WEPMS029 LANSCE RF System Refurbishment 2400
  • D. Rees, G. O. Bolme, J. T. Bradley III, S. Kwon, J. T.M. Lyles, M. T. Lynch, M. S. Prokop, W. Reass, K. A. Young
    LANL, Los Alamos, New Mexico
  The Los Alamos Neutron Science Center (LANSCE) is in the planning phase of a refurbishment project that will sustain reliable facility operations well into the next decade. The LANSCE accelerator was constructed in the late 1960s and early 1970s and is a national user facility that provides pulsed protons and spallation neutrons for defense and civilian research and applications. The refurbishment will focus on systems that are approaching 'end of life' and systems where modern upgrades hold the promise for significant operating cost savings. The current baseline consists of replacing all the 201 MHz RF systems, upgrading a substantial fraction of the 805 MHz RF systems to high efficiency klystrons, replacing the high voltage systems, and replacing the low level RF cavity field control systems. System designs will be presented. The performance improvements will be described and the preliminary cost and schedule estimates will be discussed.