1202.0180 (Andreas Ipp et al.)

Streaking At High Energies With Electrons And Positrons    [PDF]

Andreas Ipp, Jörg Evers, Christoph H. Keitel, Karen Z. Hatsagortsyan

State-of-the-art attosecond metrology deals with the detection and
characterization of photon pulses with typical energies up to the hundreds of
eV and time resolution of several tens of attoseconds. Such short pulses are
used for example to control the motion of electrons on the atomic scale or to
measure inner-shell atomic dynamics. The next challenge of time-resolving the
inner-nuclear dynamics, transient meson states and resonances requires photon
pulses below attosecond duration and with energies exceeding the MeV scale.
Here we discuss a detection scheme for time-resolving high-energy gamma ray
pulses down to the zeptosecond timescale. The scheme is based on the concept of
attosecond streak imaging, but instead of conversion of photons into electrons
in a nonlinear medium, the high-energy process of electron-positron pair
creation is utilized. These pairs are produced in vacuum through the collision
of a test pulse to be characterized with an intense laser pulse, and they
acquire additional energy and momentum depending on their phase in the
streaking pulse at the moment of production. A coincidence measurement of the
electron and positron momenta after the interaction provides information on the
pair production phase within the streaking pulse. We examine the limitations
imposed by quantum radiation reaction in multiphoton Compton scattering on this
detection scheme, and discuss other necessary conditions to render the scheme
feasible in the upcoming Extreme Light Infrastructure (ELI) laser facility.

View original: http://arxiv.org/abs/1202.0180