D. Ikeda

The atmospheric transparency measured with a LIDAR system at the Telescope Array experiment

An atmospheric transparency was measured using a LIDAR with a pulsed UV laser (355 nm) at the observation site of Telescope Array in Utah, USA. The measurement at night for two years in 2007–2009 revealed that the extinction coefficient by aerosol at the ground level is 0.033−0.012+0.016km−1 and the vertical aerosol optical depth at 5 km above the ground is 0.035−0.013+0.019. A model of the altitudinal aerosol distribution was built based on these measurements for the analysis of atmospheric attenuation of the fluorescence light generated by ultra high energy cosmic rays.

Energy Spectrum of Ultra-High-Energy Cosmic Rays Measured by The Telescope Array

The Telescope Array (TA) is a hybrid cosmic ray detector using air fluorescence detectors (FDs) and an array of surface detectors (SDs) which covers

Recent Results from Telescope Array

700 , {rm km^2}

Hybrid Measurement of the Energy Spectrum and Composition of Ultra-High Energy Cosmic Rays by the Telescope Array

in Utah. The TA Low-energy Extension (TALE) also consists of FDs with larger elevation angles and an infill SD array with 400 m spacing, which extends the observable energy range down to 4 PeV. In this contribution we present the spectrum from the TA SD, which has the largest statistics, the FD monocular spectrum, the FD-SD hybrid spectrum, and the lower energy spectrum obtained by TALE. We discuss the declination dependence of the energy spectrum in the northern sky.

Energy Spectrum and Mass Composition of Ultra-High Energy Cosmic Rays Measured by the hybrid technique in Telescope Array

The Telescope Array (TA) observatory, located in midwest Utah, USA, is designed to detect ultra high energy cosmic rays whose energy is greater than 1 EeV. TA mainly consists of two types of detector. The first type is the atmospheric Fluorescence Detector (FD). TAs three FDs have been in operation since Fall 2007. The other type of detector is a ground-covering Surface Detector (SD), which has been operating at TA since Spring 2008. In addition, the TA-Rader (TARA) and EUSO-TA associated experiments are co-located with TA, and the TA Low Energy (TALE) extension recently started partial operation. I report some recent general results from TA, and describe our future plans.The results from the Telescope Array for thee-year observations are presented. The energy spectra of ultra high energy cosmic rays measured by using the data of the fluorescence detectors, surface detectors and hybrid mode of both detectors are in good agreement. We found two break points, at 1018.69 eV as the ankle structure and at 1019.68 eV as a flux suppression. The results of the composition study with the longitudinal development observed by the fluorescence detectors show proton-dominated hypothesis. No significant anisotropies in the arrival directions observed by surface detectors are found.

Test for the Radio Detection of the Extensive Air Shower using the Electron Beam in Telescope Array

The energy spectrum and mass composition of Ultra-High Energy Cosmic Rays (UHECRs) above 10

Absolute energy calibration of FD by an electron linear accelerator for Telescope Array

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Energy measurement and spectrum by the Telescope Array

eV measured by Telescope Array (TA) are presented. TA is the largest UHECR observatory in the northern hemisphere, located in the west desert of Utah, USA. It consists of 507 Surface Detectors (SDs) and three fluorescence detectors (FDs) to observe UHECRs by those two types of detectors simultaneously, in so called hybrid observation. In hybrid analysis, a reconstruction of the longitudinal development of the air shower observed by FD with the information at the ground observed by SD, can measure the energy of the primary cosmic ray and the depth of the shower maximum precisely. The performance of the analysis, energy spectrum and mass composition of UHECR measurd by TA hybrid data is discussed.

Telescope Array Experiment

The energy spectrum and mass composition of Ultra-High Energy Cosmic Rays (UHECRs) above 1018.2 eV from the Telescope Array (TA) utilizing 6 years of hybrid data are presented. TA is a hybrid experiment consisting of fluorescence detectors (FDs) and surface detectors (SDs). We have measured the energy spectrum and mass composition using a hybrid analysis technique which uses information from both FDs and SDs. The obtained energy spectrum with a 21% energy scale uncertainty is in agreement with the results of the HiRes experiment. The mass composition measurement performed by observing the depth of shower maximum (Xmax) is consistent with a light primary model.

End-to-end absolute energy calibration of atmospheric fluorescence telescopes by an electron linear accelerator

For the future huge ultra-high energy cosmic ray observatory, we are carrying out an R&D project to search for radar echoes from cosmic ray induced extensive air showers. First the experiment with the electron beam which is generated by the Electron Light Source (ELS) in the TA site was performed. We did not find any radar echo signals but found the radio emission signals proportional to the beam current. Second we developed new experimental setup to see the radar echoes and radio emissions from the air shower in the TA site. The construction was finished on July 2014 and steady operation was started from October 2014. The design of the experiments and results of the observed signals are presented.