Nuclear Photonics

With the planned new gamma-beam facilities like MEGa-ray at LLNL (USA) or ELI-NP at Bucharest (Romania) with 10(13)gamma/s and a band width of Delta E-gamma/E-gamma approximate to 10(-3), a new era of gamma beams with energies up to 20 MeV comes into operation, compared to the present world-leading HI gamma S facility at Duke University (USA) with 10(8)gamma/s and Delta E-gamma/E-gamma approximate to 3.10(-2). In the long run even a seeded quantum FEL for gamma beams may become possible, with much higher brilliance and spectral flux. At the same time new exciting possibilities open up for focused gamma beams. Here we describe a new experiment at the gamma beam of the ILL reactor (Grenoble, France), where we observed for the first time that the index of refraction for gamma beams is determined by virtual pair creation. Using a combination of refractive and reflective optics, efficient monochromators for gamma beams are being developed. Thus, we have to optimize the total system: the gamma-beam facility, the gamma-beam optics and gamma detectors. We can trade gamma intensity for band width, going down to Delta E-gamma/E-gamma approximate to 10(-6) and address individual nuclear levels. The term nuclear photonics stresses the importance of nuclear applications. We can address with gamma-beams individual nuclear isotopes and not just elements like with X-ray beams. Compared to X rays, gamma beams can penetrate much deeper into big samples like radioactive waste barrels, motors or batteries. We can perform tomography and microscopy studies by focusing down to mu m resolution using Nuclear Resonance Fluorescence (NRF) for detection with eV resolution and high spatial resolution at the same time. We discuss the dominating M1 and E1 excitations like the scissors mode, two-phonon quadrupole octupole excitations, pygmy dipole excitations or giant dipole excitations under the new facet of applications. We find many new applications in biomedicine, green energy, radioactive waste management or homeland security. Also more brilliant secondary beams of neutrons and positrons can be produced.