The Soul of the Matter by Bruce Buff Read Free Book Online Page A

let’s go see what you came for.”
    Everyone followed Viktor down the hall and formed a small circle by the door to the reactor room.
    Viktor began, “As you may have noticed, these concrete doors are two feet thick. They shield us from the lethal neutrons generated by the reactor. Inside the large gray foam cylinder in front of you is the Alcator-E reactor. It has superconducting magnets that produce magnetic fields two hundred thousand times stronger than Earth’s. Over there are radio frequency generators where radio waves, a thousand times stronger than a radio station’s, are used to heat the plasma. When we run experiments, which we call ‘shots,’ we heat and compress the plasma intensely for up to thirty seconds. During that period, we use as much power as the entire city of Cambridge. Of course, you can’t just get that all at once from the power lines, so we build up a charge, store it in a huge flywheel, and then release it when it’s needed. Before we head over to the control room, are there any questions?”
    Instantly, a half dozen hands went up. Working left to right, Viktor picked one.
    â€œWhat do you fuel this with?”
    â€œGreat question, and something I should have already mentioned,” Viktor answered. “We use a form of hydrogen called deuterium. It has two neutrons instead of the usual one, hence the ‘deu’ in its name. An actual power-generating reactor would use a hydrogen mix that included tritium, which, as its name implies, has yet one more neutron. We don’t use tritium here because we don’t need to; it’s hard to handle, and it’s mildly radioactive, although it’s only toxic if inhaled, and it’s use is highly restricted.”
    â€œCan the reactor explode or go critical?”
    â€œNot in any sense of a nuclear explosion. There isn’t enough fuel and you can’t get runaway reactions. The worst that happens is the magnetic field fails and superheated fuel hits the walls and damages them.” Viktor pointed at the reactor and said, “Plus, with this, the hottest we get is seventy-five million degrees Celsius. For significant amounts of fusion, you need two hundred million degrees for a deuterium-to-deuterium reaction and one hundred million for a deuterium-to-tritium reaction.”
    â€œWhat happens if something does go wrong?” one student asked.
    â€œThe worst case is you can get a beam of runaway electrons that could burn through solid steel. To prevent that, we have an extinguisher that releases argon gas into the vessel if there’s a problem. This would convert the energy of the electrons into photons. The resulting light would be briefly brighter than a billion lightbulbs, or the brightest beam of light that’s ever existed.” Pausing to let the idea sink in, Viktor then said, “Now let’s head into the control room.”
    After entering the room, Viktor faced the tour group and said, “The actual shots follow a procedure a lot like a space launch, with people sitting at monitors as a recorded voice counts down. While the shot is underway, we can see computer-generated images of the plasma and readings. Before you know it, the shot is over, and you’re getting ready for another one. Pretty impressive, isn’t it? Before I conclude the tour, are there any final questions?”
    One student asked, “How do you measure the plasma temperature?”
    â€œAnother good question. Obviously, there aren’t any physical probes that could withstand the heat. What we do is bounce laser beams off the plasma. While this is an accurate enough technique, it takes time for the computers to process the data and give us a reading.”
    Mr. Reilly, stepped forward. “How far away are we from fusion energy?”
    Victor sighed. “Decades. A consortium is building a prototype reactor in France called ITER. It was supposed to take ten years, but