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Foreground: View from the roof of the Physics Research Deck. Background: The Crab Nebula University of Leeds Department of Physics & Astronomy

The South Pole Air Shower Experiment (SPASE)

The South Pole Air Shower Experiment was an array of scintillation detectors used to detect cosmic ray air showers with a central hut housing the recording electronics. This hut was known affectionately as the "SPASE shack". The array was based on the design of the GREX array at Haverah Park and operated almost continuously between 1988 and 1998 when it was decommissioned. The array consisted of 24 scintillator detectors, spaced 30m apart.

SPASE was built in an attempt to find point sources of cosmic gamma rays in the sky of the southern hemisphere and possibly provide an insight into the origin of cosmic rays.

Where was SPASE?

As the name suggests SPASE was situated in Antarctica, just 200m from the geographic South Pole!

A SPASE detector shortly after the array was built in 1988
The Amundsen-Scott Base with SPASE detectors in the foreground (photo: J.Perrett)
View of the SPASE array
The SPASE array in 1992. The large building in the foreground is an atmospheric and climate research facility known as "Clean Air"

Why build an experiment at the South Pole?

The reasons for building any experiment at the South Pole are not at first obvious. After all, the South Pole is a very harsh place to work, it is a long way from the rest of civilization, and it is expensive to send both people and equipment there.

The real reason for building SPASE at the South Pole is because objects in the sky (such as stars or galaxies which may be point sources of cosmic rays) rotate by 360 degrees once every 24 hours. Their angle above the horizon remains constant and they do not appear to rise and set like at other latitudes. This makes analysis of cosmic ray air showers easier.

Climbing into the SPASE shack through the roof!
Entrance to "SPASE shack" at the centre of the SPASE array. Originally it was possible to enter through the front door but over time snow drifts have up and the only way in is through the roof!
Working in SPASE Snow drift blocks the view from SPASE
Two views of the inside of the "SPASE shack. To the left you can see Simon Hart sitting amongst the electronics used to record data from the array. To the right is the view out of the window. Originally this gave a good view of the station but now all you can see is the snow glowing blue in the sunlight.

Why was SPASE decommissioned?

Although SPASE ran almost trouble free for over 10 years it was finally switched off in 1998. There were several reasons for this.
  • No cosmic gamma ray sources were observed. SPASE was designed to detect sources of high energy (1014 eV) gamma ray emission. Unfortunately none were found although data from the SPASE array was used to place limits on the gamma ray emission of many southern hemisphere sources.
  • Snow drifts were causing a problem. The SPASE array was built up-wind of the South Pole station and the large detectors caused large snow drifts to build up causing problems for the station. The picture at the top of this page shows a detector shortly after the array was built. By the time that the array was closed almost all of the detectors had become buried under snow.
  • A new array called SPASE-2 has now been constructed near to the Dark Sector about 1 km from the South Pole station were drifting does not cause problems. In addition the detectors used in the new array are small, flat and lie almost flush with the snow surface. Although this array will continue to search for cosmic gamma ray emission its primary goal is to investigate the composition of cosmic rays. This will be done by operating in conjunction with the VULCAN air cerenkov array and the AMANDA neutrino telescope.

    In addition to this SPASE-2 is a vital tool in the calibration of AMANDA.



Web site by the SPASEMAN   Site last updated May 13th 1999