KIP publications

"Abstract The \{AEgIS\} experiment is an international collaboration with the main goal of performing the first direct measurement of the Earth's gravitational acceleration on antimatter. Critical to the success of \{AEgIS\} is the production of cold antihydrogen ( H ¯ ) atoms. The \{FACT\} detector is used to measure the production and temperature of the H ¯ atoms and for establishing the formation of a H ¯ beam. The operating requirements for this detector are very challenging: it must be able to identify each of the thousand or so annihilations in the 1 ms period of pulsed H ¯ production, operate at 4 K inside a 1 T solenoidal field and not produce more than 10 W of heat. The \{FACT\} detector consists of two concentric cylindrical layers of 400 scintillator fibres with a 1 mm diameter and a 0.6 mm pitch. The scintillating fibres are coupled to clear fibres which transport the scintillation light to 800 silicon photomultipliers. Each silicon photomultiplier signal is connected to a linear amplifier and a fast discriminator, the outputs of which are sampled continuously by Field Programmable Gate Arrays (FPGAs). In the course of the developments for the \{FACT\} detector we have established the performance of scintillating fibres at 4 K by means of a cosmic-ray tracker operating in a liquid helium cryostat. The \{FACT\} detector was installed in the \{AEgIS\} apparatus in December 2012 and will be used to study the H ¯ formation when the low energy antiproton physics programs resume at \{CERN\} in the Summer of 2014. This paper presents the design requirements and construction methods of the \{FACT\} detector and provides the first results of the detector commissioning. "