AMANDA is a telescope for detecting high energy cosmic neutrinos. The experiment is situated in Antarctica at the Amundsen_Scott Station by the geographical south pole.
The detector consists of 680 extremely sensitive light detectors, photomultiplier tubes or PMTs for short. The PMTs are attached to cables in 19 strings which have been lowered down holes up to 2.4 kilometers deep in the antarcic ice sheet. The holes are drilled using a hot-water drill and are among the deepest holes ever made this way!
The reason for this weird setup is that neutrinos only experience the weak nuclear force. In order to see a neutrino it has to interact with something but the cross section (reaction probability) of the weak nuclear force is extremely low, so in order to see anything without waiting for ages the detector has to be huge. In antarctica there is plenty of cheap and very good detector material - ice. The deep ice has very good optical qualities and is relatively free from radioactive materials and other potential noise sources.
To see neutrinos AMANDA waits for them to interact with atoms in the vicinity of the detector. In some reactions (with muon neutrinos) muons travelling in the same direction as the neutrino are produced, and if the energy is high enough the muons emit Cerenkov light that can be detected by the PMTs. From the detection times and the amount of light detected the original neutrinos energy and direction can be calculated.
Due to the low interaction rate of neutrinos AMANDA see only a couple of neutrino reactions every day.
The main background to the neutrino signal is the flux of muons created above the detector when cosmic rays collide with the atmosphere. Atmoshpheric muon events outnumber the neutrino events by a million to one, making it very hard to distinguish neutrinos from muons. The problem is solved by looking downwards, exploiting the low interaction rate of neutrinos. The muons travel some tens of kilometer through matter whereas the neutrinos easily
passes through the entire earth with out interacting.