‘Lasetron’ could probe the nucleus
8 February 2002
Pulses of radiation short enough to probe the nucleus could be
generated with existing technology, according to physicists in
the US. Alexander Kaplan and Peter Shkolnikov have calculated
that a high-power laser could make electrons emit powerful
bursts of X-rays or gamma rays just zeptoseconds – 10-21
seconds – long. This ‘lasetron’ could also produce magnetic
fields as intense as those found near white dwarf stars (A
Kaplan and P Shkolnikov 2002 Phys. Rev. Lett. 88 074801).
The lasetron proposed by Kaplan, of Johns Hopkins University in
the US, and Shkolnikov, of the State University of New York at
Stony Brook, is based on the principle of synchrotron radiation.
Electrons accelerating in a magnetic field continuously emit
radiation, and if the electrons are moving in a circle, a stationary
observer will see a burst of radiation each time the electrons
complete a circuit.
Electronic effects in atoms, such as ionization, typically occur in
less than a femtosecond – 10-15 seconds – and these have
already been probed by pulses of radiation lasting attoseconds,
or 10-18 seconds. But nuclear processes take place about a
thousand times faster and existing synchrotrons cannot generate
bursts of radiation short enough to study them.
Kaplan and Shkolnikov believe that this problem could be solved
by using a super-powerful laser to make electrons circulate
extremely quickly. It is well known that electrons circulate in the
electromagnetic field of a circularly polarized laser. But according
to the pair, existing petawatt lasers – with outputs of 1015 watts
– could force electrons to trace out a circle just 0.1 micrometres in
radius. This would allow physicists to obtain extremely short
pulses of synchrotron rad…
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