Masaki Fukushima

Telescope Array Project for Extremely High Energy Cosmic Rays

The existence of extremely high energy cosmic rays (EHECRs) with energies exceeding 10 2 0 eV has been reported by the AGASA experiment. These cosmic rays may be produced in the active astronomical object in the outer galaxy and propagated a long distance toward the Earth. Such high energy stars have been searched in the arrival direction of these events but no clear candidates were found. A new experiment, Telescope Array (TA), is planned to unveil the enigmatic origin of the EHECRs. The physics motivation of TA is reviewed and its present status is reported.

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.

Calibration of photomultiplier tubes for the fluorescence detector of telescope array experiment using a Rayleigh scattered laser beam

Abstract We performed photometric calibration of the PhotoMultiplier Tube (PMT) and readout electronics used for the new fluorescence detectors of the Telescope Array (TA) experiment using Rayleigh scattered photons from a pulsed nitrogen laser beam. The experimental setup, measurement procedure, and results of calibration are described. The total systematic uncertainty of the calibration is estimated to be 7.2%. An additional uncertainty of 3.7% is introduced by the transport of the calibrated PMTs from the laboratory to the TA experimental site.

TA Anisotropy Summary

The Telescope Array has collected 7 years of data. We make use of these data to search for large- and small-scale anisotropy of UHECR. At small angular scales we examine the data for clustering of events and correlations with some classes of putative sources. At large angular scales we present an update of the search for localized excesses by the oversampling method previously performed with the 5-year data set [1], and examine the data for correlations with the LSS of the Universe. We confirm the existence of the hot spot of the radius 20 in the direction R:A: = 148:4, Dec: = 44:5 (equatorial coordinates) in the high-energy subset with E

Signal digitizer-finder system prototype for TA fluorescence telescope

The Telescope Array (TA) experiment plans to deploy an array of 3 fluorescence telescope stations and scintillation counter array in the west desert of Utah, and observes extremely high energy cosmic rays by the atmospheric fluorescence and air shower particles. In order to identify the origin of super-GZK (E>10/sup 20/ eV) events, TA has /spl sim/30 times larger aperture than AGASA and provides a particle identification by the shower profile measurement. Each fluorescence detector (FD) station includes 12 telescopes, and each telescope detects fluorescence light with 16/spl times/16 photomultipliers. The PMT signal caused by fluorescence is led to VME modules after amplification by the preamplifier that was united to PMT. The first module called signal digitizer-finder (SDF) bears a role of finding a first level trigger. This first level trigger is sent to track finder (TF) module, and the TF decides whether the signal is due to the air shower by finding a track. When the air shower track is found the TF sends the second level trigger to a central trigger distributor (CTD) module. The CTD collects 2nd level trigger from any TF module and distributes the information to others. Now, we started to manufacture such electronics somewhat later than the construction of the FD station and the telescopes.

Measurement of ultra-high energy cosmic rays: An experimental summary and prospects

Measurements of Ultra-High Energy Cosmic Rays achieved remarkable progress in the last 10 years. Physicists, gathered from around the world in the symposium UHECR-2012 held at CERN on February 13-16 2012, reported their most up-to-date observations, discussed the meaning of their findings, and identified remaining problems and future challenges in this field. This paper is a part of the symposium proceedings on the experimental summary and future prospects of the UHECR study.

Telescope Array search for EeV photons and neutrinos

We present the searches for photons and neutrinos with the 9 years of data of the Telescope Array surface detector (2008--2017). The both searches employ multivariate analysis with the classifier based on the Boosted Decision Tree. The diffuse flux limits for photons and down-going neutrinos are obtained for the primary energies greater than 1 EeV.

Development of atmospheric transparency measurement system

The atmospheric transparency measurement for the telescope array (TA) experiment is made by using a back-scatter LIDAR system and the central laser facility (CLF) that is a bistatic LIDAR. Both systems use a pulsed energy tripled YAG laser (355 nm). However, these systems have complementary advantages and disadvantages. A new backscatter measurement has been added to the CLF making it possible to measure, atmospheric transparency at short distances close to the surface. This new system is called LIDAR@CLF. The system and its use are discussed.

The instruments of sFLASH experiment

We will report on the setup and calibration of the instrumentation for sFLASH. The sFLASH experiment is a measurement of the air fluorescence from ∼10

Coherent radio emission from the electron beam sudden appearance

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