Ionizing Radiation Division

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Polarized 3He Program

Principals: A.K. Thompson and T.R. Gentile

Collaborators: M. Scott Dewey, Fred E. Wietfeldt (NIST)
W. Mike Snow, Xiang Fei, Dennis R. Rich, Gregory Hansen, Zema Chowdhuri (Indiana University)
Rahim Rizi (University of Pennsylvania)
Seppo Penttila, Rob Robinson, Geoff L. Greene, Mike Fitzsimmons (Los Alamos)
G.L. Jones, Hamilton College, Clinton, New York

One application of polarized 3He

The NIST polarized 3He program seeks to improve the availability of polarized 3He for applications in fundamental physics, materials science, and medicine.

These web pages are arranged to show how we produce polarized 3He and what we do with it after it is produced.  

Production

There are two optical pumping methods for producing nuclear polarization in 3He gas. Both are indirect methods in that another species is optically pumped and the polarization is transferred to the 3He nuclei. In the Metastability Exchange method, 3He metastable atoms (long-lived excited states) are optically pumped; whereas in the Spin Exchange method, rubidium is optically pumped. Spin-exchange optical pumping is a slow process that is performed directly at the pressures required for neutron polarizers, whereas in the metastable method the gas is rapidly optically pumped at low pressure and then compressed.

Most research groups pursue one or another of these techniques; ours is developing both so as to have complementary tools for particular applications.  

Applications

There are too many applications of polarized 3He to discuss on one web page, so we chose three different ones to illustrate the range of uses. One fact to keep in mind is that the applications do not really care which production method is used to make the polarized 3He.

The first two applications are in our primary field: neutron physics. The properties of 3He that make it useful in this field are described in Spin-dependent absorption in 3He.

  1. Polarization Analysis using Polarized 3He. The first neutron application is using polarized 3He to measure the polarization of a neutron beam. The example we will discuss is separating coherent and incoherent scattering in small angle neutron scattering (SANS).

  2. 3He Spin Filter for n(p,d)gamma. The second neutron application is using polarized 3He to polarize an unpolarized neutron beam. The specific example we will discuss is polarization of a spallation source neutron beam for the n(p,d)gamma experiment.

  3. Medical Imaging with Polarized 3He. The final example is using polarized 3He to image air spaces in the human body. We will briefly discuss lung imaging using polarized 3He.

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Online: November 1998   -   Last update: March 2002