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

RECORD-HIGH MAGNETIC FIELDS IN THE LAB, almost a Gigagauss in magnitude,
have been achieved by aiming intense laser light at a dense plasma,
expanding the possibilities for laboratory re-creations of astrophysical
events. At last week's APS Division of Plasma Physics Meeting in Orlando
(www.aps.org/meet/DPP02/baps/press/), researchers from Imperial College,
London, and the Rutherford Appleton Lab in the UK announced evidence of
super-strong magnetic fields that are hundreds of times more intense than
any previous magnetic field created in an Earth laboratory and up to a
billion times stronger than our planet's natural magnetic field. Such
intense magnetic fields may soon enable researchers to recreate extreme
astrophysical conditions, such as the atmospheres of neutron stars and white
dwarfs, in their very own laboratories.
At the Rutherford Appleton Laboratory near Oxford in the UK, researchers at
the VULCAN facility aimed intense laser pulses, lasting only picoseconds
(trillionths of a second), at a dense plasma. The resulting magnetic fields
in the plasma were on the order of 400 Megagauss. To determine the magnitude
of the fields, the researchers made polarization measurements of
high-frequency light emitted during the experiment. Recent measurements
presented at the APS/DPP conference suggested that the peak magnetic field
in the densest region of the plasma approaches 1 Gigagauss. Due to
technological advances peak laser intensities are likely to increase still
further and consequently even higher magnetic fields may soon be possible,
making it possible to put models of extreme astrophysical conditions to the
test. (Poster CP1.125, November 11, contact Karl Krushelnick, Imperial
College, University of London, 011-44-20-7594-7635, kmkr{at}ic.ac.uk; for
background see Tatarakis et al., Nature, 17 January 2002)

MEGAGAUSS IN PICOSECONDS.  The item above describes the creation of high
fields; this item describes the rapid measurement of high fields.
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{at}tifr.res.in; 91-22-2152971 x 2381; www.tifr.res.in )

NU APPROACH TO CP VIOLATION.  The measured abundance of helium in the
universe (about 25% of all normal matter) suggests that there is about one
proton for every 10^10 photons.  This in turn suggests that at some earlier
phase of the universe an almost equal number of protons and anti-protons
existed and gradually annihilated, but that because of some fundamental
asymmetry (at the level of one part per ten billion) in the way that the
weak nuclear force treats matter and antimatter, protons but not
anti-protons survived to the present time.  The standard model of particle
physics usually enshrines this asymmetry in the form of  "CP violation," a
mathematical convention concerning the interaction of particles in which one
imagines what happens when the charge of all the particles is reversed
(charge conjugation, abbreviated as C) and the coordinates of all particles
is reversed (the parity operation, or P).  The standard model is successful
in predicting how CP violation works out in the decay of K mesons or B
mesons (see Update 600,
http://www.aip.org/enews/physnews/2002/split/600-1.html) but not so good
at predicting where the abundance of baryons (protons plus neutrons) comes
from.
Now physicists at Hiroshima University, Niigata University (Japan) and
Seoul National University (Korea) have proposed an explanation in which the
proton excess comes (at least in part) from the decay of hypothetical heavy
neutrinos (in addition to the electron, muon, and tau neutrinos already
known).  One testable prediction of this theory is that there should be a
slight preponderance of anti-neutrinos over neutrinos, a disparity that
could be studied in the next round of neutrino oscillation experiments being
planned.  (Endoh, Physical Review Letters, 2 December 2002; contact Takuya
Morozumi, Hiroshima University, morozumi{at}hiroshima-u.ac.jp,
81-824-24-7364)

***********
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