Naoto Sakaki

Signatures of Ultra-High Energy Cosmic Ray Composition from Propagation of Nuclei in Intergalactic Photon Fields

Abstract We present a calculation of nuclei propagation with energies above 1018 eV in the intergalactic photon field. The calculation is based on a Monte-Carlo approach for the nucleus–photon interaction as well as the intergalactic magnetic field. We then assume that the ultra-high energy cosmic rays (UHECR) are nuclei which are emitted from extra-galactic point sources. Four bumps are found in the energy spectrum of the UHECR which form clusters in the distribution of their arrival directions. Based on this calculation, the energy distribution of the clustered events is discussed.

Overall View of the JEM‐EUSO Instruments

JEM‐EUSO mission with a large and wide‐angle telescope mounted on ISS has been planned to open up “particle astronomy” through the investigation of extreme‐energy cosmic rays by detecting fluorescent and Cherenkov photons by air showers developed in the earth’s atmosphere. The JEM‐EUSO telescope consists of optical Fresnel lenses with a diameter of about 2.5 m, 300 k channels of MAPMT, frontend readout electronics, trigger electronics, and system electronics. An infrared camera and a LIDAR system will be used to monitor the earth’s atmosphere.

GLOBAL MEASUREMENT OF LIGHTNING-ASSOCIATED TRANSIENT LUMINOUS EVENTS (TLEs) FROM SPACE

In this study we present possibility of continuous measurements of lightning-associated transient luminous events (sprites, elves and blue jets) from the ISS altitude using the EUSO telescope. From global lightning data we estimated possible detection rates of lightning and TLEs. We also estimated photon numbers and optical spectra of TLEs in the near-ultraviolet region (300 – 400 nm) where the fluorescence emission caused by CRs exists. These results imply that EUSO has enough capabilities to monitor not only super-GZK CRs but also global lightning and TLEs.

The focal surface of the EUSO telescope

The Extreme Universe Space Observatory (EUSO) is a space mission to study extremely high-energy cosmic rays. The EUSO instrument is a wide-angle refractive telescope in near-ultraviolet wavelength region to observe time-resolved atmospheric fluorescence images of the extensive air showers from the International Space Station. The Focal surface is an aspherical curved surface, and its area amounts to about 4.5 m2. The focal surface detector is designed as a mosaic of multianode photomultipliers (MAPMT) for the single photoelectron counting capability. The strongest requirement for the focal surface detector is the maximization of the photon detection efficiency together with the uniformity over the focal surface. We have developed a new type of MAPMT. It is modified from the ordinary one and has a grid between the photocathode and the first dynode to electrostatically demagnify the photoelectron image on the dynode. We are also developing the HV supply system for a great number of MAPMTs. EUSO experiments the day-time and night-time every 90 minutes. The heat flow must be considered to stabilize the PMT characteristics, in parallel with the heat dissipation of the electronics attached on the focal surface supporting structure.

The photo-detector for the EUSO experiment

Abstract The EUSO experiment is currently under study by ESA for a possible installation on the International Space Station. The experiment is designed to study, by means of a space-based observational apparatus, the Extensive Air Showers produced in the atmosphere by Extreme High-Energy Cosmic Rays. The design of a fast, single-photon sensitive photo-detector in the near UV, covering a large area with a few hundreds thousands pixels, and suitable for 3 years of operation in space is a challenging task. The basic aspects of the current EUSO photo-detector design, based on the presently known requirements and constraints, and the results of the preliminary studies carried on so far will be described.

Development of optical systems for the KLYPVE experiment

KLYPVE is an orbital detector of ultra high energy cosmic rays to be deployed on the Russian Segment of the International Space Station. An important part of the detector, which determines its physical parameters (energy threshold, field of view) is the optical system. For the project, a two-component system composed of a large area mirror-concentrator and a correcting Fresnel lens was developed. Two options were considered: a “Baseline” and a “Multieye telescope system” (METS). The first one consists of a 3.4 m diameter mirror and a 1.7 m lens and has 14 field of view. The second one consists of three identical telescopes with 10 field of view (a mirror of 2.4 m diameter and a 1.2 m lens) and can operate in various modes. The production of a mold for the central segment of the METS mirror was done in SINP MSU. This mold will be used for a carbon-plastic mirror manufacture. It is an important step in the development of lightweight and space qualified optical systems with high performance parameters production technology. A detailed description of the developed optical systems, optimization studies and simulations are presented as well as results of the mold production and first steps in carbon plastic mirror manufacturing.

Radiation Resistance of Nd-Doped Laser Crystals for Space Application

The radiation resistance of Nd-doped laser crystals was measured using a proton beam in order to construct spaceborne laser systems. After irradiation of 30 krad, we measured the variation of transmittance for crystals. The variation for all crystals was less than 1%. Since 30 krad is the irradiation value received over 30 years in the International Space Station with a 1-mm-thick Al cover, we conclude that all of the laser crystals have sufficient resistance for a 3-year spaceborne lidar mission at the International Space Station.

Expected number of Extensive Air Showers observable by EUSO-SPB

EUSO-SPB (Extreme Universe Space Observatory - Super Pressure Balloon) is the first path- finder mission of the JEM-EUSO program aiming at the detection of the fluorescence light emitted by Extensive Air Shower (EAS) produced by cosmic ray particles in the atmosphere. EUSO–SPB has flown in Spring 2017 from the Wanaka base in New Zealand on board a NASA Super Pressure Balloon planning to reach up to a 100 days of flight, giving, therefore, the opportunity to observe for the first time a bunch of cosmic ray events with the fluorescence technique from the edge of space. By means of the ESAF (EUSO Simulation and Analysis Framework) package, which is one of the official simulation tools to study the performance of the different pathfinder missions of the JEM-EUSO program, prior to flight, extensive simulations have been carried out to determine the expected number of detectable events as a function of several parameters related to the detector performance itself (i.e. trigger logic, optics and electronics efficiency), to the different environmental conditions (i.e. night-glow level, presence of clouds at different heights with variable optical depth) as well as to the launch season and duration of the flight. The main results of these simulation studies are presented.

Calibration system for the JEM‐EUSO mission

In order to unveil the mystery of ultra high energy cosmic rays (UHECR’s), JEM‐EUSO (Extreme Universe Space Observatory on‐board Japan Experiment Module) will observe extensive air showers induced by UHECR’s from the International Space Station orbit with huge acceptance from 2016. Calibration of the JEM‐EUSO instrument, which consists of Fresnel optics and 0.3M channel focal surface detector, is very important to discuss the origin of UHECR’s precisely with the observed results. In this paper, the calibration system before launch and on‐orbit will be reported: the calibration before flight with integrating spheres, on‐board calibration light source, and ground light source for on‐orbit calibration from ground.

Focal surface for EUSO telescope

The Extreme Universe Space Observatory (EUSO) is a wide angle refractive telescope in near-ultraviolet wavelength region to detect extremely high energy cosmic rays by observing time-resolved air-fluorescence images of the extensive air showers from the International Space Station. The focal surface detector of the EUSO is designed to be a mosaic of multianode photomultipliers to realize the single photoelectron counting capability. We describe the current status of the conceptual design and the feasibility study of the focal surface of the EUSO telescope.