Ultrabright source produces MeV-class gamma rays

Researchers at Lawrence Livermore National Laboratory (Livermore, CA) have announced first light from a novel ultrabright gamma-ray source they call T-REX (Thomson-Radiated Extreme X-rays), intended for isotope-specific, high-resolution detection and imaging applications ranging from science experiments to detection of hidden nuclear materials. The light source is built around a dual-arm laser system.

One arm of the laser system produces fourth-harmonic 263 nm spatially and temporally flattop pulses that strike a photocathode; the resulting nanoCoulomb electron bunches are accelerated to 120 MeV via a five-stage linear accelerator while keeping their 2.5 mm-mrad emittance. The second arm of the laser system produces 1 J, 10 ps amplified pulses at 1064 nm, which are frequency-tripled to provide 100 mJ, 10 ps, 355 nm pulses; these are then focused on the high-energy electron beam. The result is about 106 0.776 MeV gamma-ray photons per pulse, as detected by a cesium iodide scintillator fiber-coupled to a multichannel plate and CCD sensor array. The peak brightness of T-REX tops 1017 photons/s/mm2/mrad2/0.1%bandwidth—a result that exceeds the gamma brightness of third-generation synchrotrons (such as the Advanced Photon Source in Argonne, IL) by six to nine orders of magnitude. Contact Christopher Barty at [email protected].