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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Astron (fusion reactor) | 3/3 | https://en.wikipedia.org/wiki/Astron_(fusion_reactor) | reference | science, encyclopedia | 2026-05-05T13:03:27.177031+00:00 | kb-cron |
=== Cancellation === 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. Among the problems they noted that the Astron team had been looking "for ingenious ways to avoid or circumvent difficulties rather than to understand them." Roy Gould, head of the AEC's controlled fusion program, was specific in allowing the Astron project to continue, but only if it met a series of goals on a specific timeline. 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. Given the exciting results with the tokamak released in 1968, Hirsch favoured a program with relatively few projects each given much larger budgets. Many programs like Astron simply didn't appear to have any near-term payoff, and Hirsch was keen to cancel them. On 24 September 1972, Christofilos met with James Schlesinger of the AEC, but no record of the meeting remains. After a long day, he went to a local Holiday Inn to save a long commute home. That night he suffered a massive heart attack and died. Richard Briggs took over direction of the project until its planned shutdown date in June 1973. Under his direction, Astron returned to study of the new stabilizing field introduced by Fowler, and using single larger pulses the device hit 50% diamagnetic strength, much greater than Christofilos' efforts with pulse chains. Their final report stated that "buildup of the E-layer by multiple-pulse injection was generally unsuccessful" and noted that at the time of the shutdown they still did not understand what physics problem was limiting the buildup.
=== After Astron === Although Astron shut down, work continued with RECE at Cornell for some time. As part of their work, the team attempted to make the switch from electrons to protons. However, as some suspected, the "P-layer" proved difficult to build, and field reversal with protons was never achieved. 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. The relativistic electron ring also played a part in the bumpy torus design. This was another attempt to "plug the ends" of mirrors, by linking a number of mirrors end-to-end to form a torus. Electrons were driven to high energies not through direct injection, but external microwave-driven electron-cyclotron heating (ECH).
== Description == The Astron device consisted of two sections, the linear accelerator and the magnetic mirror "tank". These were constructed at right angles, with the accelerator's output firing into the side of the tank at one end. The tank was a relatively simple example of the magnetic mirror concept, consisting largely of a long solenoid with additional windings at both ends to increase the magnetic field in those regions and form the mirror. 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. However, there was an annular region on either end where ions of the right energy could escape, and various calculations demonstrated the rate would be fairly high. 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. The resulting field was shaped like a tube, and very similar to the Field-Reversed Configuration, or FRC. 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. Like the classic mirror, Astron injected the electrons into the mirror at a slight angle to ensure they would circulate into the center of the mirror. Today, the Astron is often considered a sub-class of the FRC concept.
== References ==
=== Citations ===
=== Bibliography === Bromberg, Joan Lisa (1982). Fusion: Science, Politics, and the Invention of a New Energy Source. MIT Press. ISBN 9780262021807. Coleman, Elisheva (4 May 2004). Greek Fire: Nicholas Christofilos and the Astron Project in America's Fusion Program (PDF). Archived from the original (PDF) on 7 January 2017. Retrieved 31 October 2011.