The detector is a 960 ton iron calorimeter surrounded by an active shield of proportional tubes. The calorimeter is comprised of 224 modules, each weighing about 4.3 tons. The modules are close packed in an array 2 high by 8 across by 14 deep to form a detector 5.4m high, 8m across and 15m long. Each module contains a tightly packed honeycomb array of 15,120 drift tubes set in a steel absorbing medium giving an average density of 1.6 gm/cc. The drift tube array provides 3-dimensional hit reconstruction, with an r.m.s. accuracy of 1.12cm in the drift direction and 3.5mm in the orthogonal plane, together with dE/dX sampling. A detailed description of the calorimeter has been published (see publications). A surface array and Cerenkov detector are operated in coincidence with the calorimeter to provide air shower information.
The detector was completed in late 1993 but data have been taken since it was one quarter built in 1989. As of early January 2000, 5 Kton-years of nucleon decay exposure have been taken. For detailed descriptions of the experiment, analysis procedures and results see the articles referenced in publications, theses and conference proceedings.
The target exposure for the experiment of 5 Kton-years has been achieved. Beyond this there is a possibility of incorporating the detector into the MINOS experiment which is designed to search for and measure neutrino oscillations and neutrino mass using a controlled, accelerator produced neutrino beam. The neutrino beam will be generated in the Fermilab neutrino beam line (near Chicago) and passed through the earth to the Soudan Mine 730 kms away where the new MINOS experiment will be located. A search for neutrino oscillations over this long baseline will cover the same region of oscillation parameters as the atmospheric neutrino anomaly reported by the Super Kamionkande and Soudan2 experiments.
For more information on the Soudan Laboratory see the visitors brochure (also available in postscript).