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!
The Amundsen-Scott Base with SPASE detectors in the foreground (photo: J.Perrett)
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.
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!
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.