Physicists at the University of Michigan have discovered a new way of separating different isotopes of the same chemical element. The technique relies on the tabletop terawatt laser--a device that can deliver up to 1 quadrillion watts (1000 terawatts) of power per square centimeter for a very short amount of time (typically 200 quadrillionths of a second). In their technique, the laser pulse enters an 18-inch vacuum chamber, where it impinges upon a target containing the isotopes of interest. The pulse heats up the target and vaporizes some of its isotopes, which escape in the form of highly excited ions (electrically charged atoms). The intense magnetic fields associated with the laser pulse exert forces on the ejected ions. The lightest isotopes end up in the center of a silicon disk (substrate) placed a couple of inches away from the target, while the heavier isotopes move out towards the edges. The researchers used this technique to separate boron-10 from boron-11 and gallium-69 from gallium-71. They envision using their technique to deposit pure thin films of isotopes directly onto microelectronic devices. (Figure courtesy Paul VanRompay, University of Michigan.)
This research is reported by P.P. Pronko et al. in the 27 September 1999 issue
of Physical Review Letters.
Link to University of Michigan news release on this work
Link to related Physics News Update item (coming September 23, 1999).