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Torrez, P. A.

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.  
WEPMS023 Progress on New High Power RF System for LANSCE DTL 2382
  • J. T.M. Lyles, S. Archuletta, D. Baca, J. Davis, D. Rees, P. A. Torrez
    LANL, Los Alamos, New Mexico
  Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396

A new 200 MHz RF system is being developed for the LANSCE proton drift tube linac (DTL). A planned upgrade will replace parts of the DTL RF system with new generation components. When installed for the LANSCE-R project, the new system will reduce the total number of electron power tubes from twenty-four to seven in the DTL plant. The 3.4 MW final power amplifier will use a Thales TH628 Diacrode. This state-of-the-art device eliminates the large anode modulator of the present triode system, and will be driven by a new tetrode intermediate power amplifier. In this mode of operation, this intermediate stage will provide 150 kW of peak power. The first DTL tank requires up to 400 kW of RF power, which will be provided by the same tetrode driver amplifier. A prototype system is being constructed to test components, using some of the infrastructure from previous RF projects. High voltage DC power became available through innovative re-engineering of an installed system. A summary of the design and construction of the intermediate power amplifier will be presented and test results will be summarized.

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.