The Variable Energy Gamma (VEGA) System is a dedicated system for delivering gamma-ray beams to users. The implementation of the VEGA System is currently underway at ELI-NP.
The system will deliver gamma-rays with energy continuously variable from 1 MeV up to 19.5 MeV covering the energy range relevant for low-energy nuclear physics and astrophysics studies, as well as applied research in materials science, management of nuclear materials, and life sciences. The beams will be quasi-monochromatic by having a relative energy bandwidth better than 0.5%, high intensity with a spectral density higher than 0.5 x 104 photons/eV/s and high degree of linear polarization at more than 95%. With these parameters, the VEGA System will be the most advanced gamma-ray source in the world having about one order of magnitude higher gamma-ray flux and at least a factor of two smaller relative bandwidth than the current state-of-the-art.
The VEGA System is based on the use of a storage ring and a high-finesse Fabry-Perot cavity. The parameters of the electron beam and of the interaction laser are optimized at the interaction point such to provide gamma-rays with the features discussed above. The electron beam system will operate in the range of 234 MeV to 742 MeV. For a given interaction laser wavelength, this electron energy range allows at least a factor of 10 in gamma-ray energy continuous tunability. Two separate optical cavity laser systems, one at ~1 μm ('IR') and one at ~0.5 μm ('Green') wavelengths, will be provided to cover the gamma ray energy range from 1 MeV to 19.5 MeV. The laser systems use a passive, high-finesse Optical Cavity to resonantly build-up pulsed laser power. The Optical Cavity provides gains of 5,000-10,000 in laser power, which reduces the complexity of the interaction laser drive system.
|Maximum Photon Energy||≥ 19.5 MeV|
|Tunability of the Photon Energy||Steplessly variable|
|Linear Polarization of Gamma-Ray Beam||≥ 95%|
|Divergence at Full Width Half Maximum (FWHM) of Beam Spot||≤ 1.5 x 10-4 rad|
|Average Relative Bandwidth of Gamma-Ray Beam (FWHM)||≤ 5.0 x 10-3|
|Total Photon Flux||≥ 1.0 x 1011 1/s|
|Time-Average Spectral Density at Peak Energy||≥ 5.0 x 103 1/(s eV)|
|Average Spectral Off-Peak Gamma-Ray Background Density||≤ 1.0 x 10-2 1/(s eV)|
|Angular Spectral Flux Density||≥ 1.0 x 109 1/(s mrad2 0.1%W)|