INFN-LNF Laboratori Nazionali di Frascati
An electron accelerator can produce a photon beam by decelerating the electrons by means of a target inside the ring. A recent technique, called Jet Target, delivers photon beams of adjustable and well defined energy without destroying the electron beam and with no harm to the ultravacuum environment of the accelerator vacuum vessel.
The Jet Target installed on ADONE in 1990 provided collisions between the stored electrons and a thin gas jet of Argon to generate the reaction e + Ar -> e + Ar + gamma , where the electron loses energy emitting a photon. The energy of the emitted photon can be measured accurately by precisely detecting the energy lost by the electron (this technique is called “tagging”).
With this facility monochromatic photon beams have been produced with high intensity (up to 7×105 tagged photons per second) in the energy range from 0.2 to 1.2 GeV, which have been exploited for a large variety of measurements on photonuclear absorption on light and heavy nuclei (up to U238) and on the production of neutral particles (gamma, neutral pion) in the photon-nucleus interaction. These experiments yield information on the influence of nuclear matter on the intrinsic properties of the nucleons and on the hadronic nature of virtual photons.
Researchers from Frascati, Genoa and Istituto Superiore di Sanita’ collaborated in this research program.