We evaluate the exposure during nadir observations with JEM-EUSO, the Extreme Universe Space Obser-\ud vatory, on-board the Japanese Experiment Module of the International Space Station. Designed as a mis-\ud sion to explore the extreme energy Universe from space, JEM-EUSO will monitor the Earth’s nighttime\ud atmosphere to record the ultraviolet light from tracks generated by extensive air showers initiated by\ud ultra-high energy cosmic rays. In the present work, we discuss the particularities of space-based obser-\ud vation and we compute the annual exposure in nadir observation. The results are based on studies of the\ud expected trigger aperture and observational duty cycle, as well as, on the investigations of the effects of\ud clouds and different types of background light. We show that the annual exposure is about one order of\ud magnitude higher than those of the presently operating ground-based observatories

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In the MICE experiment at RAL the upstream time-of-flight detectors are used for particle identification in the incoming muon beam, for the experiment trigger and for a precise timing (σ t ∼ 50 ps) with respect to the accelerating RF cavities working at 201 MHz. The construction of the upstream section of the MICE time-of-flight system and the tests done to characterize its individual components are shown. Detector timing resolutions ∼ 50 − 60 ps were achieved. Test beam performance and preliminary results obtained with beam at RAL are reported.(submitted to Nuclear Instruments and Methods A) * Corresponding author: M. Bonesini, E-mail address: maurizio.bonesini@mib.infn.it + permanent address: Department of Physics, Oxford University, UK, Published by SIS-Pubblicazioni Laboratori Nazionali di FrascatiThe MICE experiment [1] at RAL (see figure 1 for a schematic layout) aims at a systematic study of a section of a cooling channel of a neutrino factory (νF ) [2]. The 5.5 m long cooling section consists of three liquid Hydrogen absorbers and eight 201 MHz RF cavities encircled by lattice solenoids.Different neutrino factory designs require a muon cooling factor from 2 to 16, over a ∼ 100 m distance. For a cooling section prototype of affordable size, a cooling factor ∼ 10% at most may be expected. A precision of ∼ 10% on the design of the whole cooling channel implies emittance measurements at a level of 0.1% on the cooling cell prototype, thus excluding conventional emittance measurement methods, that have errors around 10%.A method based on single particle measurements has been envisaged, to obtain such a level of precision. Particles are measured before and after the cooling section by two magnetic spectrometers complemented by time-of-flight (TOF) detectors. For each particle x, y, t, p x , p y , E coordinates are measured. In this way, for an ensemble of N particles, the input and output emittances may be determined accurately. The upstream MICE time-of-flight systemIn the MICE experiment, precision timing measurements are required to relate the time of the incoming beam muons to the phase of the accelerating field in each RF cavity and simultaneously for particle identification (PID) by a TOF method. Three time-of-flight detectors (TOF0, TOF1, TOF2) are foreseen. The last two (TOF1 and TOF2) are at the entrance and the exit of the MICE cooling channel; the first one (TOF0) instead is placed about 10 m upstream of its entrance. Figure 1 shows a layout of the full MICE cooling channel with the foreseen positions of the TOF detectors. The upstream TOF detectors (TOF0, TOF1) must separate the pion contamination of the muon beam at low momenta (below ∼ 210 MeV/c) and are used for the experiment trigger. All TOF detectors are used to determine the time coordinate (t) in the measurement of the emittance.The TOF stations share a common design based on two planes of fast one-inch scintillator counters along X/Y directions (to increase measurement redundancy) read at both edges by R4998 Hamamatsu fast photomult...

n this paper we describe the main characteristics of the JEM-EUSO instrument. The Extreme Universe Space Observatory on the Japanese Experiment Module (JEM-EUSO) of the International Space Station (ISS) will observe Ultra High-Energy Cosmic Rays (UHECR) from space. It will detect UV-light of Extensive Air Showers (EAS) produced by UHECRs traversing the Earth's atmosphere. For each event, the detector will determine the energy, arrival direction and the type of the primary particle. The advantage of a space-borne detector resides in the large field of view, using a target volume of about 10(12) tons of atmosphere, far greater than what is achievable from ground. Another advantage is a nearly uniform sampling of the whole celestial sphere. The corresponding increase in statistics will help to clarify the origin and sources of UHECRs and characterize the environment traversed during their production and propagation. JEM-EUSO is a 1.1 ton refractor telescope using an optics of 2.5 m diameter Fresnel lenses to focus the UV-light from EAS on a focal surface composed of about 5,000 multi-anode photomultipliers, for a total of a parts per thousand integral 3a <...10(5) channels. A multi-layer parallel architecture handles front-end acquisition, selecting and storing valid triggers. Each processing level filters the events with increasingly complex algorithms using FPGAs and DSPs to reject spurious events and reduce the data rate to a value compatible with downlink constraints

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