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Lynch, M. T.

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.  
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.  
WEPMS033 LANSCE 201 MHz and 805 MHz RF System Experience 2412
  • K. A. Young, G. O. Bolme, J. T.M. Lyles, M. T. Lynch, E. P. Partridge, D. Rees
    LANL, Los Alamos, New Mexico
  Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396

The LANSCE RF system consists of four RF stations at 201 MHz and 44 klystrons at 805 MHz. In the LANSCE accelerator, the beam source is injected into the RF system at 0.75 MeV. The beam is then accelerated to 100 MeV in four drift tube linac (DTL) tanks, driven at 201.25 MHz. Each 201 MHz RF system consists of a train of amplifiers, including a solid state amplifier, a tetrode, and then at triode. After the DTL, the beam is accelerated from 100 MeV to 800 MeV in the forty-four coupled cavity linac (CCL) tanks at 805 MHz. The machine operates with a normal RF pulse width of 835 microseconds at a repetition rate up to 120 Hz, and sometimes operates with a pulse width up to 1.2 microseconds for single pulses. This RF system has been operating for about 37 years. This paper summarizes the recent operational experience. The reliability of the 805 MHz and 201 MHz RF systems is discussed, and a summary the lifetime data of the 805 MHz klystrons and 201 MHz triodes is presented.