Mahesh Chowdhary

Operational Experience with the CEBAF Control System

The CEBAF accelerator at Thomas Jefferson National Accelerator Facility (Jefferson Lab) successfully began its experimental nuclear physics program in November of 1995 and has since surpassed predicted machine availability. Part of this success can be attributed to using the EPICS (Experimental Physics and Industrial Control System) control system toolkit. The CEBAF control system is one of the largest accelerator control system now operating. It controls approximately 338 SRF cavities, 2,300 magnets, 500 beam position monitors and other accelerator devices, such as gun hardware and other beam monitoring devices. All told, the system must be able to access over 125,000 database records. The system has been well received by both operators and the hardware designers. The EPICS utilities have made the task of troubleshooting systems easier. The graphical and test-based creation tools have allowed operators to custom build control screens. In addition, the ability to integrate EPICS with other software packages, such as Tcl/Tk, has allowed physicists to quickly prototype high-level application programs, and to provide GUI front ends for command line driven tools. Specific examples of the control system applications are presented in the areas of energy and orbit control, cavity tuning and accelerator tune up diagnostics.

Driver assistance applications based on automotive navigation system infrastructure

Automotive navigation systems these days have access to processors with large computing power, inertial sensors, Global Positioning System (GPS) receiver, radio data service-traffic messaging channel (RDS-TMC) receiver and accurate digital map database. This enables the development of various driver assistance systems that provide greater functionality than conventional automotive navigation systems. Two such systems: adaptive front-lighting system (AFS) and curve speed warning system (CSWS) are discussed along with the architecture of the navigation system.

Development of digital feedback systems for beam position and energy at the Thomas Jefferson National Accelerator Facility

The development of beam-based digital feedback systems for the CEBAF accelerator has gone through several stages. As the accelerator moved from commissioning to operation for the nuclear physics program, the top priority was to stabilize the beam against slow energy and position drifts (<1 Hz). These slow drifts were corrected using the existing accelerator monitors and actuators driven by software running on top of the EPICS control system. With slow drifts corrected, attention turned to quantifying the higher frequency disturbances on the beam and to designing the required feedback systems needed to achieve the CEBAF design stability requirements. Results from measurements showed the major components in position and energy to be at harmonics of the power line frequencies of 60, 120, and 180 Hz. Hardware and software was installed in two locations of the accelerator as prototypes for the faster feedback systems needed. This paper gives an overview of the measured beam disturbances and the feedback systems developed.

A prototype fast feedback system for energy lock at CEBAF

The beam energy of CEBAF must be controlled accurately against phase and gradient fluctuations in RF cavities in order to achieve a 2.5/spl times/10/sup -5/ relative energy spread. A prototype fast feedback system based on the concepts of modern control theory has been implemented in the CEBAF control system to function as an energy lock. Measurements performed during the pulsed mode operations indicate presence of noise components at 4 Hz and 12 Hz on beam energy. This fast feedback prototype operates at 60 Hz rate and is integrated with EPICS. This paper describes the implementation of the fast feedback prototype, and operational experience with this system at CEBAF.