Calibration of Photomultiplier Tubes for the Fluorescence Detector of Telescope Array Experiment using a Rayleigh Scattered Laser Beam

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.Comment: 43 pages, 15 figure

The Telescope Array Experiment: Hybrid Measurement of Ultra High Energy Cosmic Rays in Northern Hemisphere

Abstract The result of AGASA shows the extension of the cosmic ray energy spectrum above the GZK cut-off. Several new generation experiments are planned or under construction to identify the origin of such ultra high energy (UHE) cosmic rays exceeding the cut-off. We report here the design of hybrid Telescope Array (TA) and introduce plans of improving the accuracy of measuring the energy spectrum by the hybrid measurement of ground array and air fluorescence telescope

Future plans for the Telescope Array experiment

The Telescope Array (TA) experiment is the world's first and the only air shower detector to be directly calibrated by an on-site accelerator beam. For wider and deeper understanding of cosmic rays via high precision measurements, we have several future plans for the TA experiment. The first extension plan is an on-going project, called as TA low energy extension (TALE), to extend the sensitive energy range to 1016.5 eV in order to study the second knee, the predicted galactic-extragalactic transition of dominant sources and air shower phenomena comparing with LHC measurements. The second proposition is exchanges of FDs and SDs between TA and Pierre Auger Observatory, toward understanding systematic uncertainties of these experiments and to solve discrepancies in energy scales and Xmax. The third plan is a huge air shower array, “the world observatory”, consisting of a huge number of SDs and/or FDs for the world's largest exposure and the finest accuracy to open a new window on astronomy with ultra high energy particles

Telescope Array Experiment

The Telescope Array is the largest hybrid cosmic ray detector in the Northern hemisphere designed to measure primary particles in 4 PeV to 100 EeV range. The main TA detector consists of an air shower array of 507 plastic scintillation counters on a 1.2 km square grid and fluorescence detectors at three stations overlooking the sky above the air shower array. The experiment and its recent measurements - spectrum, composition, and anisotropy - is reviewed. Recently the construction of the TA Low energy Extension (TALE) detector, which consists of an additional fluorescence detector and an infill array, was finished. TALE lowers the energy threshold of TA down to 4 PeV. We are also constructing the TAx4 detector to increase statistics in particular at the highest energies. The current status and the future prospects of these new TAx4 experiments is reported