SLAC, Menlo Park, California
IHEP Beijing, Beijing
XAL is a high level accelerator application framework originally developed by the Spallation Neutron Source (SNS), Oak Ridge National Laboratory. The XAL framework provides generic hierarchical view for an accelerator as well as many utility tools. In XAL, a built-in physics model calculates either single particle or envelope tracking for physics parameters. Modifications to the original XAL model are necessary for the Linac Coherent Light Source (LCLS). Work was done to manipulate MAD deck output within a database in support of the XAL configuration and model. The XAL graphical user interface has been replaced by a SLAC specific design. New applications based on the framework are also discussed.
SLAC, Menlo Park, California
At SLAC (SLAC National Accelerator Laboratory) the CD (Controls Department) is developing a new Multi-Device Knob Utility based on the EPICS * (Experimental Physics and Industrial Control System) toolkit for controlling more or more PVs (Process Variables) in unison, or simultaneously, from a physical knob located in the control room, or from various software tools such as EDM (EPICS Extensible Display Manager) or a Swing slider in Java. A group of devices are hooked up to a knob, then the value written to the devices is a simple function of the value of the knob. This is used, most commonly, to create a bump in the electron beam for LCLS (Linac Coherent Light Source). Control system variables typically controlled are magnetic fields, phases, and timing offsets. This paper describes the technologies used to implement this utility.
* http://www.aps.anl.gov/epics
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.
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.
SLAC, Menlo Park, California
At SLAC (SLAC National Accelerator Laboratory) the CD (Controls Department) is developing a physics application framework based on the Java(tm) programming language developed by Sun Microsystems. This paper will discuss the first application developed using this approach: a new Orbit Display. The software is being developed by several individuals in reusable Java packages. It relies on EPICS * (Experimental Physics and Industrial Control System) toolkit for data collection and XAL ** (A Java based Hierarchy for Application Programming) for model parameters. The Orbit Display tracks and displays electron paths through the LCLS (Linac Coherent Light Source) in both a graphical, beam line plot, and tabular format. It contains many features that may be unique to SLAC and is meant to be used both in the control room and by individuals in their offices or at home. Unique features include BSA (Beam Synchronous Acquisition), Orbit Fitting, and Buffered Acquisition.
* http://www.aps.anl.gov/epics
** http://neutrons.ornl.gov/APGroup/appProg/xal/xal.htm
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.
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.