• 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.

• 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.

• G. R. White, S. Chevtsov, P. Chu, D. Fairley, E. Grunhaus, R. D. Hall, P. Krejcik, G. S. McIntyre, D. Rogind, R. C. Sass, H. Shoaee, S. Zelazny
  SLAC, Menlo Park, California

Rapid development of scientific software applications for a large instrument like an accelerator, in an established and evolving environment, is made difficult by the diversity of interfaces, protocols, and hosts, of the source data. Additionally, analytical applications deal mainly with complex data structures, such as synchronized beam data for a whole beamline, rather than individual control points. AIDA (Accelerator Integrated Data Access) is a distributed 3-tier system that allows Matlab, Java programs, or scripts, to interoperate with EPICS Channel Access, legacy control systems, relational databases such as Oracle, accelerator modelling systems, EPICS and SLC Archivers, and other data servers, in ways oriented to scientific users. It also includes a web interface for search and plots. At SLAC, AIDA provides a uniform, fast, interface to 4.5 million named elements in 14 lower level systems, over two control systems, for about 70 utilities and 20 large scientific applications. This approach was found to be key to the rapid commissioning of LCLS at SLAC. We present the first public description of the developed AIDA system since its early thinking at ICALEPCS 2001.