Stan B. Thomas

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.

Steerable laser system for UV atmospheric monitoring at the High-Resolution Fly's Eye

Monitoring the aerosol component of the lowest 10 km of the atmosphere at UV wavelengths (300 - 400 nm) is an important part of the High Resolution Flys Eye astrophysics experiment. Our method of atmospheric monitoring uses a frequency tripled YAG laser and a steering system that can point the beam anywhere in the sky. The same detector that measures scintillation light from high energy cosmic rays also measures light scattered from this laser system over a range of laser energies, geometries, and polarizations. This paper describes the technique, the laser system, and some recent measurements.

The Prototype Opto-mechanical System for the Fluorescence detector Array of Single-pixel Telescopes

We present the opto-mechanical design of a new generation fluorescence telescope for the de- tection of ultrahigh-energy cosmic rays (UHECRs). The Fluorescence detector Array of Single- pixel Telescopes (FAST) is a proposed low-cost, large-area, next-generation experiment for the detection of UHECRs via the atmospheric fluorescence technique. The telescope is of a simpli- fied Schmidt design, suitable for a camera consisting of only a few large pixels. The telescope has a 1 m2 entrance aperture, and a field-of-view of 30◦ × 30◦ . We present the optical design of the prototype telescope as well as the mirror alignment and pointing calibration procedures. The prototype of the FAST telescope is installed at the Black Rock Mesa site of the Telescope Array Experiment.

First results from the full-scale prototype for the Fluorescence detector Array of Single-pixel Telescopes

The Fluorescence detector Array of Single-pixel Telescopes (FAST) is a design concept for the next generation of ultrahigh-energy cosmic ray (UHECR) observatories, addressing the requirements for a large-area, low-cost detector suitable for measuring the properties of the highest en- ergy cosmic rays. In the FAST design, a large field of view is covered by a few pixels at the focal plane of a mirror or Fresnel lens. Motivated by the successful detection of UHECRs using a prototype comprised of a single 200 mm photomultiplier-tube and a 1 m^2 Fresnel lens system [Astropart.Phys. 74 (2016) 64-72], we have developed a new full-scale prototype consisting of four 200 mm photomultiplier-tubes at the focus of a segmented mirror of 1.6 m in diameter. In October 2016 we installed the full-scale prototype at the Telescope Array site in central Utah, USA, and began steady data taking. We report on first results of the full-scale FAST prototype, including measurements of artificial light sources, distant ultraviolet lasers, and UHECRs.

Atmospheric studies using the high-resolution fly's eye xenon flasher array

The High Resolution Flys Eye (HiRes) cosmic ray detector at Dugway Utah, measures UV scintillation light from extensive air showers. The detection technique is calorimetric in that the amount of light produced is proportional to the energy of the primary particle. Primary particle energies range from 1017 to more than 1020 electron volts. The detector can measure air showers more than 30 km away, a distance of several atmospheric extinction lengths. Variations in the atmosphere can cause significant variations in the amount of light reaching the detector. Atmospheric monitoring is extremely important. This paper discusses a method, under development, that uses the HiRes detector to measure light scattered from pulsed collimated xenon flashbulb sources (Flashers). Discussion includes a description of the light sources and a preliminary data analysis to extract a measurement of atmospheric extinction length and scale height.