The Frascati LINAC beam facility performance and upgrades

Abstract

est beam and irradiation facilities are key enabling infrastructures for research in HEP and astro-particles. In the last 11 years the Beam-Test Facility (BTF) of the DA$\Phi$NE accelerator complex, in the Frascati Laboratory, has gained an important role in the European infrastructures devoted to the development and testing of particle detectors. Electron or positron beam can be extracted -- before the injection into the damping ring -- to a dedicated transfer line, where a system composed by a target plus a dipole and collimating slits, can attenuate and select the momentum of secondary particles in narrow (<1\%) band. The secondary beam is then driven to a dedicated experimental hall for beam-test activities. The facility can provide run-time tuneable electrons and positrons beams in a defined range of different parameters: energy (up to 750 MeV for $e^-$ and 550 MeV for $e^+$), charge ( up to $10^{10}$ particles/bunch) and pulse length (1.4--40 ns). The bunch delivering rate is depending on the DA$\Phi$NE injections (up to 49~Hz). The electron beam spot and divergence can be adjusted, down to sub-mm sizes and approximately 2 mrad in air. Photons can be produced on a Bremsstrahlung active target, and energy-tagged inside a dipole magnet by means of Silicon micro-strip detectors. Overall, an average of 200 beam days is delivered to about 20 experimental groups each year. The possibility of delivering an high-intensity positron beam, opens the opportunity of performing positron annihilation missing mass experiments for the search of light dark matter particles, like dark photons: recently the PADME experiment has been approved by INFN for running at the BTF starting in 2018. An important upgrade program of the facility is under way, along three main lines: consolidation of the LINAC infrastructure, in order to guarantee a stable operation in the longer term; upgrade of the LINAC energy, in order to increase the facility capability (especially for the almost unique extracted positron beam); doubling of the BTF beam-lines, in order to cope with the significant increase of users due to the much wider range of applications.