Particle accelerators are not the most obvious machines to use for generating energy. And yet the idea that they could produce more power than they consume is not entirely far-fetched, as pointed out today by Robert Wilson, an accelerator physicist who was the driving force behind the creation of Fermilab near Chicago.
Wilson died in 2000 but a paper he wrote on this topic in 1976 has now found its way onto the arXiv and it highlights some thought-provoking ideas.
At the time, Wilson was director of Fermilab where he was building an accelerator called the Energy Doubler/Saver, which employed superconducting magnets to steer a beam of high energy protons in a giant circle. These protons were to have energies of up to 1000 GeV.
The Energy Doubler was special because it was the first time superconductivity had been used on a large scale, something that had significant implications for the amount of juice required to make the thing work. “One consequence of the application of superconductivity to accelerator construction is that the power consumption of accelerators will become much smaller,” said Wilson. And that raised an interesting prospect.
Imagine the protons in this accelerator are sent into a block of uranium. Each proton might then be expected to generate a shower of some 60,000 neutrons in the material and most of these would go on to be absorbed by the nuclei to form 60,000 plutonium atoms. When burned in a nuclear reactor, each plutonium atom produces 0.2 GeV of fission energy. So 60,000 of them would produce 12,000 GeV.
Using this back-of-an-envelope calculation, Wilson worked out that a single 1000 GeV proton could lead to the release of 12,000 GeV of fission energy. Of course, this neglects all the messy fine details in which large amounts of energy can be lost. For example, it takes some 20MW of power to produce an 0.2MW beam in the Energy Doubler.
But even with those kinds of losses, it certainly seems worthwhile to study the process in more detail to see if overall energy production is possible.
Wilson’s conclusion is this: “There are probably better ways of producing plutonium, but it does appear that it would be feasible to construct an intense proton accelerator that would produce more energy than it consumes.”
30 years later, accelerator technology has moved on but in a way that surely makes Wilson’s ideas even more pertinent–accelerators today are even more energy efficient than they were in 1976. And given the blue skies thinking associated with power generation today, these ideas may well be worth revisiting.
They may also solve another problem. Interplanetary spacecraft such as Galileo and Cassini rely on plutonium batteries for power. But NASA’s stocks of plutonium are running low so nobody is quite sure how future generations of these vehicles will get their juice. Wilson’s approach could help.
However, it also raises the ugly spectre of proliferation. The possibility of making plutonium on this scale using 30-year old accelerator technology must surely be of more than passing concern for anybody worried about the spread of technology that could lead to nuclear proliferation.
That’s a potential fly in the ointment that may need greater attention..