Friday, April 09, 2010

Measurement of an "Exotic" Nucleus

Nuclear physicists at the Argonne National Laboratory in the US have obtained the first results from a new spectrometer that contains the magnet from a mothballed MRI machine. They used the Helical Orbit Spectrometer (HELIOS) to make the most precise measurements to date of two excited states of boron-13 – an "exotic" nucleus containing an unusually high ratio of neutrons to protons. The researchers say that HELIOS could eventually yield precise data on the structure of a range of rare nuclei.

Carried out at Argonne's ATLAS facility, the experiment involves slamming a beam of stable boron-11 nuclei, containing five protons and six neutrons, into a gas cell filled with much lighter deuterium nuclei, which have just one proton and neutron. This method of rare-isotope production – known in the trade as "inverse kinematics" – leads to neutrons being "stripped" from the deuterium and tacked onto the nuclei in the beam. The result is a "secondary" beam of short-lived boron-12 nuclei containing seven neutrons.

It's a rather amusing, and some time confusing, situation there at Argonne. You got a nuclear physics accelerator/collider facility named ATLAS in the Physics Division. But there's also members of the ATLAS collaboration in the High Energy Physics Division working on the ATLAS detector at the LHC! I'm sure the Physics Division would argue that their ATLAS were there long before the LHC was even a glimmer in someone's eyes. Still, it made for many confused look, especially for visitors and people not familiar with nuclear/high energy physics.