New radioactive isotope diagnostics set up

Posted by Lerner on Mar 04, 2011 at 06:07 PM
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Thanks to a suggestion by Dr. Subramanian concerning possible medical radioisotope applications, FF-1 now has a new diagnostic instrument—a Geiger counter—to monitor short-lived radioactive elements. This new instrument will help us to measure the ion energy in the plasmoid and, possibly, in the ion beam.

When small amounts of nitrogen are introduced into the fill gas, high energy deuterons can collide with the nitrogen to produce radioactive oxygen-15, with a half-life of only 2 minutes. The oxygen-15 emits a positron which is annihilated by an electron, producing two 511-keV gamma rays. These can penetrate the vacuum chamber wall and be counted by our new digital Geiger counter.

Since the d-N reaction occurs at higher energies than the d-d reaction, the number of oxygen-15 nuclei produced is a second, independent measure of how hot the plasmoid is. Although we expect 1,000 times fewer d-N reaction than d-d reactions, on larger shots, we do expect to see a measurable signal.