Astron (fusion reactor)
The Astron is a type of fusion power device pioneered by Nicholas Christofilos and built at the Lawrence Livermore National Laboratory during the 1960s and 70s.
He had first started work along these lines in the late 1940s while running an elevator installation company in Greece,[1] and in 1948 he wrote a letter to what was then the University of California's Radiation Laboratory at Berkeley outlining several ideas on accelerator focusing.
[2] Around the same time, Ernest Courant, Milton Stanley Livingston, and Hartland Snyder of Brookhaven National Laboratory were considering the same problem and devised the same solution, writing about it in the 1 December 1952 issue of Physical Review.
The electrons would be captured in the mirror, and build up a layer of current near the outside surface of the tank volume, which he called the "E-layer".
[6] This arrangement solved one of the main problems with the basic magnetic mirror concept, which had open field lines at the ends.
[8] In 1956, Christofilos finally received his security clearance, and he immediately moved to what was now the Lawrence Livermore National Laboratory (LLNL) to start work on the Astron concept.
After two years enough progress had been made that he was able to present the idea at the 1958 Atoms for Peace conference in Geneva, along with a model of the system they proposed to build.
Christofilos solved this by introducing resistor wires that slightly slowed the electrons after entering the tank, so they no longer possessed the energy needed to flow back out.
[16] Funds for the upgrades were eventually granted, but only at the cost of direct oversight by an Ad Hoc Panel created by the AEC.
By this point the "conventional" designs, the stellarator and magnetic mirror, had long been working on real-world plasmas and were slowly increasing the pressures and temperatures.
[19] Christofilos had already considered this and suggested that an operational design would use protons in place of the electrons, and would not suffer from the same level of energy losses.
Christofilos went ahead with this change and started testing in 1971; this demonstrated greatly improved performance both with the reduction in current and success in trapping the electrons.
Christofilos was unimpressed; this design would not be useful for a steady state fusion generator, only by continually adding pulses could the machine maintain itself.
[22] Faced with the continued problems with Astron, and the seeming ease that the RECE team had managed to reach the goals they had originally suggested in 1968, a second Ad Hoc Panel published a scathing report.
[24] When Robert Hirsch took over the AEC's controlled fusion arm in 1972, he instituted a sweeping review to classify the approaches under study and eliminate duplication and low-payoff projects.
The last version of this effort, FIREX, shut down in 2003, having demonstrated what appears to be a purely theoretical reason why the Astron concept will never work.
[30] In a simple mirror the ions in the fuel plasma were injected at an angle so they could not simply flow right out of the ends where the field was roughly linear.
By injecting electrons into the mirror before the fuel, the E-layer would create a second magnetic field that would cause the annular areas to fold back into the center of the tank.
[30] The main difference between these devices is the way the field reversal is achieved; with the E-layer in the Astron, and by currents in the plasma for the FRC.
