• S. R. Norum, S. Allison, S. Chevtsov, J. E. Dusatko, K. D. Kotturi, P. Krejcik, J. J. Olsen, T. Straumann, A. J. Tilghman
  SLAC, Menlo Park, California

A state-of-the-art Machine Protection System for the SLAC Linac Coherent Light Source has been designed and built to shut off the beam within one pulse during 120 Hz operation to protect the facility from damage due to beam losses. Inputs from beam loss monitors, BPMs, toroids and position switches of insertable beam line devices are connected to a number of Link Node chassis placed along the beam line. Link Nodes are connected with a central Link Processor in a star topology on a dedicated gigabit Ethernet fiber network. The Link Processor, a Motorola MVME 6100, processes fault data at 360 Hz. After processing, rate limit commands are sent to mitigation devices at the injector and just upstream of the entrance of the sensitive undulator beam line. The beam's repetition rate is lowered according to the fault severity. The SLAC designed Link Nodes support up to 96 digital inputs and 8 digital outputs each. Analog signals are handled via standard IndustryPack (IP) cards placed on the Link Node motherboards with optional transition boards for signal conditioning. A database driven algorithm running on the Link Processor provides runtime loadable and swappable machine protection logic.

• D. Fairley, S. Allison, S. Chevtsov, P. Chu, F.-J. Decker, P. Emma, J. C. Frisch, T. M. Himel, K. H. Kim, P. Krejcik, T. E. Lahey, H. Loos, P. Natampalli, S. Peng, D. Rogind, H. Shoaee, T. Straumann, G. R. White, E. Williams, J. Wu, S. Zelazny
  SLAC, Menlo Park, California

Beam-based feedback control loops are required by the Linac Coherent Light Source (LCLS) program in order to provide fast, single-pulse stabilization of beam parameters. Eight transverse feedback loops, a 6x6 longitudinal feedback loop, and a loop to maintain the electron bunch charge were successfully prototyped in MATLAB for the LCLS, and have been maintaining stability of the LCLS electron beam at beam rates up to 30Hz. In the final commissioning phase of LCLS the beam will be operating at up to 120Hz. In order to run the feedback loops at beam rate, the feedback loops will be implemented in EPICS IOCs with a dedicated ethernet multi-cast network. This paper will discuss the design of the beam-based Fast Feedback System for LCLS. Topics include MATLAB feedback prototyping, algorithm for 120Hz feedback, network design for fast data transport, actuator and sensor design for single-pulse control and sensor readback, and feedback configuration and runtime control.

• P. Krejcik, S. Allison, A. Chan, S. Chevtsov, P. Chu, D. Fairley, E. Grunhaus, D. Rogind, H. Shoaee, G. R. White, E. Williams, S. Zelazny
  SLAC, Menlo Park, California

The successful commissioning this year of the LCLS has been the culmination of a significant effort to integrate new, state-of-the-art controls with legacy controls of the SLAC linac. A distributed controls system of EPICS IOCs and Linux servers operates in conjunction with an older, centralized VMS system based on CAMAC and micros. High-level Java applications and scripts written in Matlab provide data acquisition and analysis tools for diagnosing, tuning and optimizing the machine. A RDB unites the configuration control, online modeling and reference beam data within a uniform schema. The Aida data access tool allows applications transparent access to data from either control system and has allowed engineers to control migration to new platforms without requiring changes to application code. Emphasis has shifted from using our SLC-aware IOC development to supporting a data bridge in the opposite direction to provide access for burgeoning applications on new platforms to data from the old control system. The challenge has been to provide such data synchronously with the timing system on a pulse-by-pulse basis at 120 Hz to support beam-based feedback and other applications.