Separation Anxiety...

Lithium-7 as a test case was successfully purified by magnetically activated and guided isotope separation with the lab setup shown here. The oven for heating lithium is sitting on the red lab jack to the right. Circular view ports were used for shining lasers to optically pump the isotopes. Inside the rectangular box are the magnetic guides.

THOMAS MAZUR
Citation: Phys. Today 69, 9, 22 (2016); http://dx.doi.org/10.1063/PT.3.3292

Topics: Atomic Physics, Isotopes, Mark G. Raizen, Research, Thermodynamics

Atomic beams, optical pumping, and magnet geometry are the crux of a fledgling method that may help meet the demand for pure isotopes.

Mark Raizen didn’t set out to separate isotopes. But a few years ago the University of Texas at Austin physicist realized that the methods he was using to cool atoms to near absolute zero could be adapted to enrich isotopes, and he had a hunch his approach—magnetically activated and guided isotope separation (MAGIS)—could help satisfy the growing demand for isotopes.

Fundamental research, medicine, energy, and other markets are finding new and growing applications for isotopically enriched materials, both stable and radioactive. “Many isotopes have been expensive and rare. They’re like an untapped natural resource,” says Raizen. It’s not unusual for enriched stable isotopes to cost $50 000 per gram, he notes.

Separation anxiety

For decades, the main instrument for separating stable isotopes has been the calutron, which was first built in 1941 and separates by charge-to-mass ratio (see the article by Bill Parkins, Physics Today, May 2005, page 45). A sample is ionized, accelerated with electric fields, and then deflected with magnetic fields. Because different isotopes of a given element have the same charge but vary in mass, they become separated in a magnetic field, with heavier isotopes deflected less. The US shuttered its last calutrons in the 1990s. Today the bulk of the world’s stable isotopes come from national inventories and from decades-old calutrons in Russia. Radioisotopes are made in reactors and accelerators around the globe.

Physics Today: Can MAGIS work magic for separating stable isotopes? Toni Feder