1. Low Background Studies at the Soudan Underground Laboratory-9/20/2002 1 Low Background Studies at the Soudan Underground Laboratory The Soudan Underground Lab is located at a depth of 710 m, 2100 mwe at 47.8° N., 92.3° W Two main rooms, each ~15 m wide by ~12 m high—CDMS II Lab is ~70 m long, MINOS Lab is ~95 m long About 1/2 of existing space is available now or by mid-2003 Muon flux <1/100 m -2 -s -1 ; rock radioactivity typical of other sites Marvin L. Marshak University of Minnesota

2. Low Background Studies at the Soudan Underground Laboratory-9/20/2002 2 Soudan Laboratory Layout CDMS II (Soudan 2) Lab Mine Shaft MINOS Lab

3. Low Background Studies at the Soudan Underground Laboratory-9/20/2002 3 Soudan Laboratory Assets Existing space with utilities and management/staff infrastructure experienced in installation and operation of science experiments (Soudan 2,  decay, MINOS, CDMS II) Neutrino beam (in 2005) Critical mass of scientific activity—MINOS and CDMS II Support facilities for scientists—housing, etc. Experience with liability, permitting, environmental and legal issues The Soudan Lab is currently the largest Neutrino and Subterranean Science (NeSS) laboratory in the United States

4. Low Background Studies at the Soudan Underground Laboratory-9/20/2002 4 Access to Underground Lab Three compartment shaft with each compartment ~4 ft. x 6 ft. Maximum length ~33 ft. Maximum weight ~9 T Skilled staff has moved bridge cranes, front end loaders, 5,500 T MINOS Detector, CDMS II cryogenics etc. to underground lab

5. Low Background Studies at the Soudan Underground Laboratory-9/20/2002 5 Active Shield Technology Muon rate at Soudan is already low enough for some experiments: supernovae, semiconductors etc. Soudan 2 used active shield—veto when muon passes through or near region of detected energy

6. Low Background Studies at the Soudan Underground Laboratory-9/20/2002 6 Active Shield Technology Most serious backgrounds are muon-induced neutrons and gammas Gammas are mostly short- range Rock radioactivity backgrounds are independent of depth Recent data and models suggest neutrons are reasonably well- understood E neutron vs. E µ (Y. F. Wang et al.)

7. Low Background Studies at the Soudan Underground Laboratory-9/20/2002 7 Active Shield Technology LVD Data on Neutron Distance and Time (M. Aglietta et al.)

8. Low Background Studies at the Soudan Underground Laboratory-9/20/2002 8 Future Plans The Soudan Underground Laboratory is an active and exciting location to do science and technology Seek potential users to collaborate in active shield design and implementation (likely experiment specific) For further information: Earl Peterson eap@mnhep.hep.umn.edu, Priscilla Cushman prisca@physics.umn.edu or Marvin Marshak marshak@umn.edu eap@mnhep.hep.umn.edu prisca@physics.umn.edu marshak@umn.edu