pdf of the issue - Symmetry Magazine

symmetry
A joint Fermilab/SLAC publication
PO Box 500
MS 206
Batavia Illinois 60510
USA
symmetry
explain it in 60 seconds
Synchrotron radiation
is the light
emitted by
charged particles as they accelerate—whether they’re gaining
speed along a straight line or traveling at a constant speed
on a curved path. (Moving along a curve involves acceleration;
we feel this type of acceleration when we drive a car around
a corner.)
Synchrotron light gets its name from the synchrotron
particle accelerators where it was first observed. Synchrotrons
use magnets to bend the paths of speeding electrons into
arcs. But we also see it in the cosmic realm: some of the light
emitted by astronomical objects such as the Crab Nebula
comes from electrons swooping through galactic magnetic
fields.
When accelerated, low-mass particles such as electrons
lose far more energy to synchrotron radiation than heavy
particles like protons do. That’s why scientists use electrons,
not protons, to harvest the power of synchrotron radiation
in facilities called light sources. There the electrons travel in
circles or slalom through magnets known as wigglers or
undulators. They radiate extremely intense light in a direction
tangential to the curved path they’re on, like mud flung from
a spinning tire or sparks from spinning fireworks. Scientists
choose a specific wavelength of light from the broad range
that the electrons emit, including infrared, ultraviolet, X-ray,
and visible light, and focus it on very small samples. The
combination of intensity and tunability makes synchrotron
radiation a powerful all-purpose tool for research in many
fields, yielding detailed information on structures as small as
atoms and molecules.
Herman Winick, SLAC National Accelerator Laboratory