Y. Tameda

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.

An Event Reconstruction Method for the Telescope Array Fluorescence Detectors

We measure arrival directions, energies and mass composition of ultra‐high energy cosmic rays with air fluorescence detector telescopes. The longitudinal profile of the cosmic ray induced extensive air shower cascade is imaged on focal plane of the telescope camera. Here, we show an event reconstruction method to obtain the primary information from data collected by the Telescope Array Fluorescence Detectors. In particular, we report on an “Inverse Monte Carlo (IMC)” method in which the reconstruction process searches for an optimum solution via repeated Monte Carlo simulations including characteristics of all detectors, atmospheric conditions, photon emission and scattering processes.

Central Laser Facility Analysis at The Telescope Array Experiment

The Central Laser Facility (CLF) is the laser device which shoots the vertical laser. CLF is located at the Center of the Telescope Array (TA) experiment site. The TA has three fluorescence detectors. CLF is equidistant from three FD stations. We made the CLF simulation using the same program as the cosmic‐ray simulation. Using the CLF simulation, we reconstruct the energy shot by the CLF. In this paper, we describe some results of CLF reconstruction comparing the difference of reconstructed energy between two fluorescence telescopes.

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.

ALPAQUITA Array in the ALPACA Project

We are now proposing a new project which consists of a large air shower array (83,000 m^2) and a muon detector array (5,400 m^2) located at the altitude of 4,740 m near La Paz in Bolivia to observe 100 TeV gamma rays in the southern sky. The ALPAQUITA array is a prototype air shower array which will be constructed at the ALPACA site. This array consists of 45 scintillation counters of 1 m^2 in area each, and its effective area is approximately 8,000 m^2 (1/10 of ALPACA air shower array). In the present paper, we report on the current status and the performance of the ALPAQUITA array

TA fluorescence detector calibration by UV LED with an unmanned aerial vehicle

We are developing a fluorescence detector (FD) calibration device called as Opt-copter which consists of an UV LED, a high accuracy GPS and an unmanned aerial vehicle (UAV). Opt-copter is a standard light source to be used to calibrate the Telescope Array (TA) FDs. The primary characteristic of Opt-copter is its high portability which enables us to put the light source on any position we want in the F.O.V. of FDs. Our upgraded UAV, has improved flight reliability and payload capacity. The calibration procedure is established by a test observation at the TA FD site. We evaluated the flight accuracy and developed a method to measure the FD geometry. We will report the current status of Opt-copter.

The Cosmic Ray Air Fluorescence Fresnel lens Telescope (CRAFFT) for the next generation UHECR observatory

The flux of the ultra high energy cosmic rays (UHECRs) is extremely low, hence we need a huge observatory for UHECR research. On the other hand, the larger the scale of the observatory, the higher the construction cost. In order to launch the next generation UHECR observatory, we should reduce their construction cost, dramatically. Therefore, we are developing a simple structure fluorescence telescope. The telescope consists of a 1 m

The overview of the ALPACA Experiment

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Calibration of a fluorescence detector using a flying standard light source for the Telescope Array observatory

Fresnel lens, an 8 inch photomultiplier tube, a UV transmitting filter, and a FADC board. We will report the status and the result of the test observation at the Telescope Array site.

Trigger electronics of the new Fluorescence Detectors of the Telescope Array Experiment

The ALPACA experiment is a new project aimed at wide field-of-view nhigh-sensitivity observations of high-energy cosmic rays and cosmic ngamma rays, launched between Bolivia and Japan in 2016. It is composed nof an 83,000 m