Optics and Nuclear Photonics

Abstract

Our discovery that the scattering of γ quanta from the very large electric fields of nuclei, called Delbrück scattering , results in a much larger real part of the index of refraction for γ‐rays than anticipated has manifold consequences. All older perturbative quantum electrodynamics ( QED ) predictions for a few million electronvolt γ‐rays by the first‐order Born approximation fail by many orders of magnitude and a new, more complex nonperturbative QED has to be applied. As the expected cross sections are now much larger, other nonperturbative high‐field QED effects such as photon splitting or an enhanced pair production close to the threshold are being investigated to study and understand this new high‐field QED with the ultrahigh electric fields of the nucleus. At the same time, the much larger Delbrück scattering allows to develop γ‐ray optics of up to about 10 MeV, with new focusing lenses and much more efficient γ monochromators. In combination with the development of much more intense, brilliant γ beams, this opens a new field of nuclear photonics. We, for the first time, will selectively excite individual nuclear levels for diagnostics of isotopes or their transmutation. The strongly penetrating γ beams focused to micrometer diameters open up new fields of diagnostics in medicine, green energy, nuclear waste management, and so on. We can produce about 50 new medical radioisotopes for cancer therapy or for the diagnostics of dose delivery to the tumor. Also, other brilliant secondary sources, such as cold neutron sources or moderated positron beams, can be produced, which open new ways for material or surface sciences.