N.R. Wild

A cloud monitoring system for remote sites

A cloud monitor has been developed for use with cosmic ray air shower fluorescence detectors, the High Resolution Flys Eye and the Pierre Auger Observatory. This is based on an infrared thermopile device which, unlike previous such monitors, requires no moving chopper and is suitable for unattended operation over long periods of time.

Reflectometer for fast measurements of mirror reflectivity

A safe and inexpensive, hand-held reflectometer has been developed to provide reflectivity measurements near one wavelength for mirrors in the field and laboratory. The principle used is: the specular reflection of a parallel collimated light beam from an LED, focused onto a large area pin diode, so that the beam throughout is always intercepted. The beam is chopped and filtered by an electronic circuit to make it immune to fluorescent and other ambient light conditions except bright sunlight. The response is shown to be linear and the 100% point can be calibrated by an extension tube which brings the beam in line with the detector, or a fresh aluminium mirror can be used. The small power drain enables the calibration to be retained.

Geometrical reconstruction with the High Resolution Fly's Eye prototype cosmic ray detector

Abstract The High Resolution Flys Eye EHE cosmic ray detector (HiRes) was operated for over two years (prior to November 1996) in a two-site prototype configuration. This paper describes the development and testing of an event reconstruction method for extensive air showers (EAS) viewed in coincidence by both sites (stereo viewing). The reconstruction accuracy was directly measured through the use of a UV laser mounted on a telescope that generated airshower-like events with known geometries. For events observed with stereo opening angles greater than about 10° (most events) the median error in the reconstructed laser direction was 0.4° with 95% of events being reconstructed with errors of less than 0.9° (which degrade to 0.8° and 1.8°, respectively, for smaller opening angles). A limited investigation of the likely performance of the HiRes Stage 1.0 detector was undertaken. Reconstruction accuracy is likely to be only slightly degraded compared with the prototype results.

Fast rise time, long pulse width, kilohertz repetition rate Q-switch driver

We describe a versatile Pockels cell Q-switch driver that can generate high voltage electrical pulses having both fast rise times and long duration, with a repetition rate in excess of 1 kHz. The circuit is simple and easily adaptable to most types of Q-switched lasers and regenerative amplifiers.

Prospects for 1019eV cosmic ray studies in South Australia

Abstract We discuss some of the important elements necessary for the successful operation of a very large cosmic ray array. Some of these points are illustrated using a detector Monte Carlo. The importance of composition measurement is stressed, particularly in regard to anisotropy interpretation. We review some of the issues connected with the other uncertainty in anisotropy studies, the galactic magnetic field, and show that with reasonable assumptions about its large scale structure, an experimental site in the southern hemisphere would have a good view of both the Virgo cluster region and the Magellanic Clouds. The features of a possible site at Woomera in South Australia are discussed. Finally, some technical aspects of solar power and communication technology are reviewed. Some options for the array control, data collection procedures and system timing are outlined.

IACT array performance and design study for multi-TeV gamma-ray astronomy

We outline here preliminary performance estimates of an array of modest‐sized (24 m2) Cherenkov imaging telescopes for multi‐TeV γ‐ray astronomy. We have considered an example sparse array of 9 cells of 5 telescopes arranged in a sparsely separated grid, for which the intercell spacing is 1.5 km, and each cell has a side telescope spacing of 500 m. Cosmic‐ray background rejection makes use of scaled Hillas‐based parameters, and additionaly, we incorporate direction reconstruction exploiting the time development of Cherenkov images, aiming to improve the imaging method at large core distances (typically >200 m). In the energy range we focus on at present, 10 to 100 TeV, this array provides energy flux sensitivities approaching 3×10−13 erg cm−2 s−1, representing a factor 5 to 10 improvement over H.E.S.S. A low altitude (0.2 km) site also provides an improved collection area vs. that obtained at a medium altitude (1.8 km). These preliminary results serve as useful guide in designing a telescope array for mul...

A Cosmic Ray Muon Detector for Astronomy Teaching

Practical astronomy is usually taught using optical telescopes or, more rarely, radio tele- scopes. For a similar cost, complementary studies may be made of astrophysical particles through the use of a modestly sized muon detector. Such a detector records the arrival of cosmic ray particles that have traversed the heliosphere and the rate of muon detections reflects the flux of those particles. That flux is controlled by the day to day properties of the heliosphere which is in a state of constant change as the outflowing solar wind is affected by solar activity. As a consequence, a laboratory muon detector, whose count rate depends on the state of the heliosphere, can be an interesting and useful teaching tool that is complementary to optical or radio studies of the Sun.

The CANGAROO Project: Very High Energy Gamma-ray Astronomy at Woomera

In this paper the Very High Energy (VHE) gamma-ray astronomy program at the University of Adelaide is described. VHE gamma rays with energies above ~5 × 10 11 eV are observed using the atmospheric Cerenkov technique. Results from the first three years observations at Woomera and the current upgrading of the telecope are described. The CANGAROO project, a collaboration between the University of Adelaide and a number of Japanese institutions, is also introduced.

Absolute calibration and intercalibration of photomultipliers for the measurement of Cherenkov light intensities

Abstract We describe a technique for the absolute calibration of photomultipliers for the detection of lighthaving a Cherenkov spectrum. This technique utilizes the Chernekov light generated by single vertical cosmic ray muons in a horizontal ultraviolet transmitting glass plate. For use at a field station, a similar, but less time consuming, technique employing the ungated spectrum from a perspex (acrylic) cylinder is described. We discuss the use of temperature-stabilized LEDs for continuous monitoring of gain changes due to factors such as photomultiplier fatigue or temperature variations.

Analysis Techniques at large core distances for multi‐TeV Gamma Ray Astronomy

We present analysis techniques specific to multi‐TeV extensive air showers (EAS). Our emphasis is on Cherenkov imaging at large core distances. Such techniques are being developed for the simulation study of TenTen, a proposed array of Imaging Atmospheric Cherenkov Telescopes (IACTs) optimized for the multi‐TeV regime, which aims for a collecting area of 10 km2 above energies of 10 TeV. Preliminary results using timing information from EAS are discussed with a view to improving shower reconstruction and background rejection for one simulated cell of the array. Based on these findings a direction reconstruction algorithm is implemented that gives an improvement in angular resolution of ∼30% over our standard geometric reconstruction for shower energies above 10 TeV.