Rapid measurement of high fields.
From PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 614 November 20, 2002 by Phillip F. Schewe, Ben Stein, and
James Riordon


Physicists from the Tata Institute and the Institute for Plasma
Research in India have recorded in detail, for the first time, the
huge magnetic spike encountered by atoms in a sample bearing the
brunt of an intense laser shot.
Fields as great as 27 megagauss, roughly 50 million times the
strength of Earth's magnetic field, come about very quickly in the
following way: the 10^16-watt/cm^2 pump laser beam strikes an
aluminum target, the surface layer of atoms is quickly ionized, and a
stream of very fast electrons is released into the body of the
target, inducing the huge field. Many high-power lasers around the
world study the effects of intense light upon a solid sample. The
chief achievement of the Indian researchers is to look at this
process with unprecedented temporal precision, monitoring the rising
magnetic field in femtosecond intervals by watching the polarization
of a delayed secondary laser beam reflected from the particle plasma
engulfing the sample.
Femtosecond knowledge of megagauss fields might have a bearing on
designs for nuclear fusion reactions, and for studying other
subjects where high magnetic fields are important—NMR, Hall effect,
and perhaps even fast magnetic information storage and switching
devices. (Sandhu et al., Physical Review Letters 25 November 2002;
contact G. Ravindra Kumar, Tata Institute, grk@...; 91-22-
2152971 x 2381; www.tifr.res.in )