A Star is Born Twice Daily at the University of RochesterPush-Button Nuclear FusionFusion has long been the dream. Coupling an inexhaustible energy source (extracted from sea water) with no long-half-life radioactive byproducts, it offers the ultimate in energy independence. It’s the stuff of suns and stars. And in a modern, tree-shaded building in upstate New York, on an average of more than twice daily for the past twelve years, the pressures, temperatures, and energies of fusion have been given birth for brief moments at the University of Rochester’s Laboratory for Laser Energetics.
Fifty Million Degrees in the ShadeThe upgraded Omega—a 60-beam, frequency-tripled glass laser—has an implosion velocity of 105meters/s a power of 5 x 1013watts, and a fuel temperature of 5 x 107°C. That’s more energy than generated — albeit for short periods of time — by the entire U.S. electrical power grid. The laser can be fired about once an hour, and has an expected service life of at least 10,000 target shots. Control system complexity increased over the original design by a factor of five: there are over 10,000 control and data acquisition points, including more than 3000 A/D channels, 2000 DC servo motors, and 4000 digital I/O channels. And how is this vast system organized and coordinated? With a LonWorks based control network. Canosa and his engineers rapidly concluded that only a scalable, distributed control system would facilitate both ease of installation and maintenance, and anticipated future expansion. Off-the-shelf availability of LonWorks components from such suppliers as Motorola (Austin, Texas), Echelon (Palo Alto, California), and Distributed Controls (Webster, New York) was also seen as a key feature, as this allowed the designers to concentrate more on application development, and less on the details of the individual pieces. Hierarchical Design a NecessityCanosa’s group decided on fairly conventional card cage packaging, creating a series of application-specific motherboards for various purposes. About a dozen different types have been produced to date. Each such card, functioning as a node in the overall network, incorporates a generic daughterboard, which in turn is constructed around a single Neuron 3150 Chip. This chip incorporates the three microprocessors, and much of the program memory, communication, and I/O device control circuitry necessary to implement the functions of a LonWorks network node. Up to ten of these “node cards” communicate across the passive backplane of a single card cage; as many as 50 cages occupy a single twisted-pair communication channel. “Software is also pivotal in the Omega upgrade,” notes Canosa. “Network variables supported by LonWorks technology align well with the object-oriented design of the executive processes.” With a network node count already approaching 2000, such well structured organizational strategies are critical to the design. John Canosa has moved on to a new position, with new opportunities to exploit LonWorks technology. But it hasn’t taken his replacement, Jeff Kramer, very long to get up to speed. When asked his initial opinions of the new architecture, he opined that “doing it without Neuron Chips would have been a nightmare.” Even to the casual observer, the results are dramatic: despite a threefold increase in system size, there’s now room for bowling in the capacitor bay.
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