A gamma-ray telescope using nuclear emulsions allows observations of stellar objects in the 0.01–100 GeV energy region with high angular resolution, polarization sensitivity, and large aperture area. ...The Gamma-Ray Astro-Imager with Nuclear Emulsion (GRAINE) project is designed to enable high-precision observation of cosmic gamma rays through the use of balloon-borne emulsion telescopes. We have developed a balloon-style pressure vessel gondola for the GRAINE 2018 balloon-borne experiment. It enables us to maintain robust and vacuum-packed emulsion chambers even at balloon altitudes. The greater part of the vessel is made of membrane materials consisting of ultra-thin polyurethane-coated polyester fabric. It is lightweight and portable, and can be used to expand the mounting area of the detector, unlike mostly metal vessels. Moreover, the absorption of signal gamma rays and background gamma-ray production due to interactions between cosmic rays and the vessel can be minimized. The pressure vessel gondola, equipped with a 0.38-m2 emulsion telescope and other equipment, was launched on April 26, 2018. During the whole observation (17 h 21 m), the internal pressure was kept above 230 hPa. The GRAINE project will start scientific observation using enlarged telescopes and the pressure vessel gondola is planned to include an expansion of the mounting area of the detector to ∼10 m2 while following the design on the GRAINE 2018 model.
Electromagnetic cascades in matter, photon fields, and magnetic fields are solved by a standard numerical method, integrating the diffusion equations of respective cascade processes numerically. Our ...results and those of Aharonian and Plyasheshnikov agree very well for cascades in matter and magnetic fields, though they show some slight discrepancies for cascades in photon fields of high incident energies. Transport properties of electron and photon spectra are also investigated by solving differential-difference equations for cascades with simplified cross-sections, and the spectra under the electron cooldown process are well explained quantitatively.
Extensive air showers (EASs) originated from primary cosmic ray energies above 1015 eV have been measured at multiple EAS observatories deployed in Japan since Sept. 1996. The typical EAS array has ...been located at the rooftop of the buildings in the university campus, and has GPS-disciplined 10 MHz oscillator to provide the UTC time stamp for each EAS event within a few μs accuracies. Searching for simultaneous and parallel EAS events at multiple EAS observatories due to Gerasimova-Zatsepin (GZ) effects have been carried out by comparing EAS arrival time stamps and directions detected by several baseline combinations of EAS arrays. The EAS pairs whose time difference and angular distance were less than 5 ms and less than 15° respectively, were selected and their angular distances from the solar direction and the lunar direction were examined. The data were compared with numerical GZ probability as a function of arrival directions of cosmic ray nuclei. Consequently, significant excesses of these events in the solar direction as expected in the numerical prediction of GZ effects were not found. We however found that the deficiencies of EAS pairs in the lunar direction, but its deviation is not significant.
We have installed a shift register system of extensive air show (EAS) particles in a compact EAS array built on the rooftop of the Faculty of Engineering building in the campus of Okayama University ...of Science and being operated since April 2006 as part of Large Area Air Shower (LAAS) experiments , in order to register each arrival time of EAS particles within 5 μs. Detector simulations based on the database obtained from one of the standard cosmic ray propagation simulator in the atmosphere (AIRES) have also been carried out and the procedures to estimate the primary cosmic ray energy from the Linsley's method have been developed and examined. Applying Linsley's method to the EAS data obtained by our EAS arrays and the simulation results, we derived the energy spectrum from 10 16 eV to 1019.5 eV. Consequently, we obtained the power-law index of -3.2 (+0.46-0.8) in the primary energy range of 1016 eV to 1018.5 eV, and obtained that a change around 1018 eV appeared if not taking account of the zenith angle distribution of primary cosmic rays. We compared the obtained energy spectrum with other experimental data above 1016 eV energies, and showed the two components of power-law energy spectra well described our data. We also showed the improvement of energy resolution by applying the restriction of zenith angle of primary cosmic rays in our simulation results, as well as the potential of the Linsley's method with a compact EAS array.
Very high energy spectra of cosmic ray nuclei from the JACEE balloon experiments are presented. From a total of 12 balloon flights with an exposure factor of about 580 m
2 hour the energy spectra of ...nuclei have been obtained in the energy range from several TeV to 1,000 TeV. Proton energy spectrum, extending to several hundred TeV, can be a single-power law. Helium shows a single power law spectrum in the energy range from 2 TeV/n to 200 TeV/n. Other nuclei up to Fe indicated harder spectral indices compared with those of protons and helium. The composition at around 500 TeV is 16 ± 5%: 29 ± 5%: 35 ± 5%: 9 ± 3%: 11 ± 4%, for the abundance of p : He : C ∼ O : Ne ∼ S : Z ≥ 18.
