  Petawatt-class lasers can produce multi-GeV electron beams through laser
wakefield electron acceleration. As a by-product, the accelerated electron
beams can generate broad synchrotron-like radiation known as betatron
radiation. In the present work, we measure the properties of the radiation
produced from 2 GeV, 215 pC electron beams, which shows a broad radiation
spectrum with a critical energy of 515 keV, extending up to MeV photon energies
and 10 mrad divergence. Due to its high energy and flux, such radiation is an
ideal candidate for gamma-ray radiography of dense objects. We employed a
compact betatron radiation setup operated at relatively high-repetition rates
(0.1 Hz) and used it to scan cm-sized objects: a DRAM circuit, BNC and SMA
connectors, a padlock and a gas jet nozzle. GEANT4 simulations were carried out
to reproduce the radiograph of the gas jet. The setup and the radiation source
can reveal the interior structure of the objects at the sub-mm level, proving
that it can further be applied to diagnose cracks or holes in various
components. The radiation source presented here is a valuable tool for
non-destructive inspection and for applications in high-energy-density physics
such as nuclear fusion.
