1. E. W. Grashorn and A. Habig, UMD, for the MINOS Collaboration The Detectors of The Main Injector Neutrino Oscillation Search (MINOS) Experiment The MINOS experiment uses two scintillator and steel detectors, along with a muon neutrino beam, to search for  disappearance, and thus neutrino oscillations. The Near Detector is located at Fermi National Accelerator Laboratory in Batavia, IL, 1 km from the Neutrinos at the Main Injector (NuMI) beam, 90 m underground, and measures the manufactured neutrino flux. The Far Detector is situated in a former iron mine in the Soudan Underground Mine State Park in Northeastern MN, 700 m (2070 mwe) below the surface, and measures the neutrino flux after they have traveled the 735 km baseline. The detectors have nearly identical instrumentation to allow for a reduction of systematic errors in the Near/Far comparison. This Poster supported by NSF RUI grant #0354848. MINOS is supported by the U.S. Department of Energy, the U.K. Particle Physics and Astronomy Research Council, and the State and University of Minnesota. Near Detector Size – 980 ton mass, 282 3.8 m x 4.8 m “squashed octagons” (153 instrumented), 16.6 m long. The 120 planes in the upstream region are instrumented, four with partially (shown) and the fifth fully. The diameter of the beam at this location is small enough that full instrumentation of each plane is unnecessary. QIE Electronics – Fast readout electronics that can handle the high event rates at the Near Detector (as compared to the Far Detector) Photomultiplier Tubes – Hamamatsu M64, 64 pixel PMT The detectors are composed of vertically hung, low-carbon steel, octagonal planes. Each plane has a hole in the center to allow the passage of a current carrying wire that create a 1.5 T magnetic field in the detectors. The active detector is compsed of 4 x 1 cm scintillator strips, polystyrene coextruded with a TiO 2 coating for increased light retention, arranged in 20 or 28 strip modules. Strips are oriented at 45 o to the horizontal, alternating positive and negative, to create an orthogonal planar coordinate system. Light flashes created in the scintillant are transmitted via Wavelength Shifting (WLS) fibers to the Photomultiplier tubes (PMTs) contained in the Multiplexing (MUX) boxes. Far Detector Size – 5400 ton mass, 486 8 m diameter octagons, 31.5 m long. Every plane is fully instrumented. Veto Shield – Eliminates downward going muons arriving between planes that appear as neutrino induced, allowing for atmospheric neutrino analysis. Cosmic Rays – 0.5 Hz cosmic ray rate. The Far Detector is a useful cosmic ray detector because of its size, depth, and its magnetic field that allows for charge sign determination. Photomultiplier Tubes – Hamamatsu M16, 16 pixel PMT The WLS fibers absorb the UV light created by an energetic particle interacting with the scintillator, then re-emit green light. The green light emitted by the WLS fibers are transmitted to the electronics by clear fibers. The fiber “cookie” is the interface of the detector with the PMT. The PMTs are made by Hamamatsu, and they have multiple pixels that allow a single PMT to read many fibers. Near Detector Far Detector Special Thanks M. Kordosky Special Thanks M. Kordosky Special Thanks M. Kordosky The first beam neutrino event in the Far Detector. It is a rock muon induced by a charged current anti-neutrino interaction upstream of the detector. The curvature is immediately apparent in the X-Y view, and gives away the negative charge of the interacting muon, and that the momentum is 12 GeV. The U and V views show how far the muon traveled in the detector for the particular type of plane; U planes oriented -45 o from the horizontal, the V planes oriented +45 o from the horizontal. U View V View A near detector neutrino interaction. The U view is in the top frame, the V view is in the middle frame, and the X-Y view is in the lower left. The event displays tend to be more complex at the near detector because of the higher neutrino flux. There are also muons induced in the rock that appear in the near detector. MINOS PRELIMINARY! Neutrino induced muons Rock muons Summary The installation of the MINOS is complete, and the detectors are currently taking data. The near detector sees a few neutrinos per beam spill, the far sees a beam neutrino every few hours. For more information see the proceedings paper for this poster http://arxiv.org/hep-ex/0507018.