The Extreme Universe Space Observatory (EUSO), onboard the Japanese Experiment Module (JEM) of the International Space Station (ISS), is a project led by Japan, with contributions from the United States, Italy, Germany, France, Spain, Switzerland, Russia, South Korea and Mexico. It is devoted to the detection of ultra high-energy cosmic particles with energies E>7x1019eV, which are revealed through emission in the atmosphere of Cherenkov and fluorescence light in the near-UV region. Current experiments are all ground-based. A big enhancement would rise from space, since a bigger atmospheric target could be monitored. However, since at these high energies the signal is faint and the probability of detection is very low (~1 Km-2 century-1), the optical system must have a large aperture, wide Field of View (FoV) and be necessarily lightweight. This project is the continuation of the EUSO mission, led by ESA, stopped some years ago at the end of phase A, and JEM-EUSO is currently at the end of phase A. For both experiments, a ~2.3 m Entrance Pupil (EP) diameter and a 60° FoV were required to achieve the science goals. However, for the present configuration, the constraint of the maximum stowable dimensions of the JAXA's H-II Transfer Vehicle (HTV) unpressurized cargo area forces the instrument to have maximum transverse dimensions of 2.65 x 1.9 m2. Reflective optics, in the form of a properly designed Schmidt camera, are not yet suitable for this purpose, since these optical requirements would need a large, deployable, primary mirror. The main challenge for designing the current configuration consists in developing an unusual combination of large and lightweight refractive optics: two double-sided curved Fresnel lenses and a central curved Fresnel + diffractive lens, in UV-grade PMMA and/or CYTOP, have been considered. This paper describes the development of such a system, focusing on the possible choices of materials and overall optical design, which is responsibility of the authors. Performances of the latest configurations are also presented.
Hirohiko Shimizu, M. Ameri, F. Cadoux, Osvaldo Catalano, C. Chapron, S. Cuneo, Toshikazu Ebisuzaki, Flavio Fontanelli, Valerio Gracco, Philippe Gorodetzky, Yoshiya Kawasaki, P. Musico, Patric Nedelec, T. Patzak, M. Pallavicini, Alessandro Petrolini, E. Plagnol, F. Pratolongo, Mario Sannino, Naoto Sakaki, Yoshiyuki Takahashi, M. Takeda, Yoshiyuki Takizawa, Masahiro Teshima
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.
Superconduting tunnel junctions (STJ) have been developed to detect X-ray ~ visivle photons for application to astrophysics, particle physics, material physics, and so on. STJ are applicable as photon detectors with good energy resolution and a high photon-counting rate. STJ also have good efficiency because of their high absorption efficiency below 1 keV photon energy. That is advantageous in the observation of the faint objects with which the photon number is limited like astronomical objects and planetary plasma observation. STJ have potentials to open new windows of telescope. On the other hand, the progress of multilayers makes it possible to fabricated a normal incidence telescope (NIT) with high angular resolution and wide field of view up to 500 eV photon energyThe combination of the improved optical elements (multilayer) and STJ will enable us to design a new optical system in the near future. We demonstrate the design combined Visible - X-ray Wide-Band Space Telescope (WBST).
We have been developing a neutron lens and prism based on neutron refractive optics. As a neutron has a magnetic dipole moment, it is accelerated in a magnetic field gradient. Thus, we can control a neutron beam free from beam attenuation using the magnetic field gradient. Moreover, its spin dependence of the acceleration is profitable in the case of using the polarized neutron beam. The sextupole magnetic field functions as a focusing or defocusing lens for neutrons depending on the neutron spin states. The focusing and defocusing effects of a prototype sextupole magnet was experimentally studied. By combining focusing and defocusing functions of the sextupole magnet, we can control the neutron beam shape and divergence more flexibly. Adiabatic and nonadiabatic field connections make it possible to realize the magnetic doublet system. A quadrupole magnetic field functions as a neutron prism, which were experimentally confirmed. The neutron spin and energy dependence of the refracting power is applicable to an analysis of the neutron spin and energy. In this paper, the details of the experimental results of the magnetic devices are described and their applications in the neutron scattering experiment are discussed.
We have developed compound refractive prism for cold neutrons. To prevent an increase in neutron absorption, we have developed prism array like a Fresnel lens. The prism characteristics were investigated with experimental and numerical simulation studies. We achieved transmission of 0.75 and refractive angle of 7.5 mrad for 15 neutrons with 49 layered prism array.
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