At the core of the AGILE scientific instrument, designed to operate on a satellite, there is the Gamma Ray Imaging Detector (GRID) consisting of a Silicon Tracker (ST), a Cesium Iodide Mini-Calorimeter and an Anti-Coincidence system of plastic scinti
llator bars. The ST needs an on-ground calibration with a $gamma$-ray beam to validate the simulation used to calculate the energy response function and the effective area versus the energy and the direction of the $gamma$ rays. A tagged $gamma$-ray beam line was designed at the Beam Test Facility (BTF) of the INFN Laboratori Nazionali of Frascati (LNF), based on an electron beam generating $gamma$ rays through bremsstrahlung in a position-sensitive target. The $gamma$-ray energy is deduced by difference with the post-bremsstrahlung electron energy cite{prest}-cite{hasan}. The electron energy is measured by a spectrometer consisting of a dipole magnet and an array of position sensitive silicon strip detectors, the Photon Tagging System (PTS). The use of the combined BTF-PTS system as tagged photon beam requires understanding the efficiency of $gamma$-ray tagging, the probability of fake tagging, the energy resolution and the relation of the PTS hit position versus the $gamma$-ray energy. This paper describes this study comparing data taken during the AGILE calibration occurred in 2005 with simulation.
The MEG detector is designed to test Lepton Flavor Violation in the $mu^+rightarrow e^+gamma$ decay down to a Branching Ratio of a few $10^{-13}$. The decay topology consists in the coincident emission of a monochromatic photon in direction opposite
to a monochromatic positron. A precise measurement of the relative time $t_{e^+gamma}$ is crucial to suppress the background. The Timing Counter (TC) is designed to precisely measure the time of arrival of the $e^+$ and to provide information to the trigger system. It consists of two sectors up and down stream the decay target, each consisting of two layers. The outer one made of scintillating bars and the inner one of scintillating fibers. Their design criteria and performances are described.
