The Status of the STACEE Observatory

TL;DR

STACEE is a ground-based gamma-ray observatory using heliostat mirrors to detect Cherenkov light, aiming to study astrophysical gamma sources in the 50-500 GeV range, with recent upgrades and promising preliminary results.

Contribution

This paper details the design, construction, and initial performance of the STACEE observatory, including recent upgrades and early gamma-ray detection from the Crab Nebula.

Findings

Detected gamma-rays from Crab Nebula during initial observations

Achieved an energy threshold below 70 GeV

Enhanced electronics and readout systems implemented

Abstract

The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is a ground-based instrument designed to study astrophysical sources of gamma radiation in the energy range of 50 to 500 GeV. STACEE uses an array of large heliostat mirrors at the National Solar Thermal Test Facility in Albuquerque, New Mexico, USA. The heliostats are used to collect Cherenkov light produced in gamma-ray air showers. The light is concentrated onto an array of photomultiplier tubes located near the top of a tower. The construction of STACEE started in 1997 and has been completed in 2001. During the 1998-99 observing season, we used a portion of the experiment, STACEE-32, to detect gamma-rays from the Crab Nebula. The completed version of STACEE uses 64 heliostat mirrors, having a total collection area of 2300 m^2. During the last year, we have also installed custom electronics for pulse delay and triggering, and 1 GHz Flash ADCs to read out the photomultiplier tubes. The commissioning of the full STACEE instrument is underway. Preliminary observations and simulation work indicate that STACEE will have an energy threshold below 70 GeV and a reach for extragalactic gamma-ray sources out to redshift of ~1.0. In this paper we describe the design and performance of STACEE.