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The MINOS far detector
SUPPLEMENTS ELSEVIER
The MINOS
Nuclear
Physics
B (Proc.
Suppl.)
118 (2003)
468
Far Detector
Alec Habiga* , for the MINOS Collaboration aUniv. of Minnesota Duluth, Physics Dept., 10 University Dr., Duluth, MN 55812
The Main Injector Neutrino Oscillation Search (“MINOS”) experiment will be a complete fiontto-back ucl disappearance oscillation study. An intense V~ beam (“NuMI”) will be produced using protons from the Main Injector and characterized by a ‘LNear Detector” at Fermilab. 735 km to the northwest, the V~ beam will be observed again by the “Far Detector” at the Soudan Mine Underground Lab in northern Minnesota. This Far Detector is a larger version of the Near Detector, to minimize potential systematic differences. The difference between the observed up spectra at the two detectors will provide a precision measurement of the parameters involved in the up +) V, oscillations observed in atmospheric neutrinos. The Far Detector is a Steel/Scintillator sampling calorimeter, composed of 486 planes of 1” thick, 8m diameter steel octagons sandwiched with layers of 1 cm thick plastic scintillator. The steel provides target mass and passive calorimetry and the scintillator emits light at the passage of charged particles. The layers are hung perpendicular to the beam direction, making the complete detector 31 m long, 8 m in diameter, and 5.4 kt in mass. The steel will be magnetized by a 1.5 T field to provide charge discrimination. The layered structure provides good energy resolution for both penetrating and showering particles, and reliably distinguishes between the e, p, and x resulting from v interactions. The scintillator layers are composed of parallel, 4.1 cm wide, optically isolated strips. Light is channeled out of the plastic by wavelength shifting optical fiber, and carried from the edges of the detector by clear optical fiber to photomultiplier tubes (“PMT”s). *The poster
presenter gratefully acknowledges from the NSF through its RUI
O920-5632/03/$ - see front matter doi: 10.1016/SO920-5632(03)01363-X
support for grant #0098579
Q 2003 Elsevier
Science
this
B.\!
The fast timing of the scintillator light allows directional determination, and the experiment uses GPS timing to gate on the beam spill back at Fermilab. Construction began in August 2001. The first half of the detector is nearly completed, and when finished in July 2002 will be magnetized while the second half of the detector is assembled. Each of the planes is independently instrumented, allowing each plane to contribute to the data acquisition soon after it is physically installed. Although the NuMI beam will not turn on until the beginning of 2005, cosmic ray muons cross the detector at a rate of -lOOOp/strip/month. This is a great aid to the commissioning and calibration of the detector. Hardware problems are found and fixed quickly, and data acquisition and reconstruction software can be developed and tested on this real data. In particular, the problem of resolving the eight-fold ambiguity produced by multiplexing eight fibers to one PMT channel has been resolved. Taking advantage of the cosmic ray muons, which travel in straight lines at close to the speed of light, the geometry of the detector can be verified and the response calibrated. Channel-tochannel timing offsets are measured for later subtraction, and the timing resolution is found to be a 2.6 ns. The first atmospheric neutrino events have also been observed while looking through this collection of commissioning data. Two upward-going muon events have so far been recorded, although analyses of contained neutrino events are still being refined. This work ensures that when the NuMI beam is turned on, the MINOS Far Detector will be taking quality data from the very start. All rights
reserved.
The MINOS
Nuclear
Physics
B (Proc.
Suppl.)
118 (2003)
468
Far Detector
Alec Habiga* , for the MINOS Collaboration aUniv. of Minnesota Duluth, Physics Dept., 10 University Dr., Duluth, MN 55812
The Main Injector Neutrino Oscillation Search (“MINOS”) experiment will be a complete fiontto-back ucl disappearance oscillation study. An intense V~ beam (“NuMI”) will be produced using protons from the Main Injector and characterized by a ‘LNear Detector” at Fermilab. 735 km to the northwest, the V~ beam will be observed again by the “Far Detector” at the Soudan Mine Underground Lab in northern Minnesota. This Far Detector is a larger version of the Near Detector, to minimize potential systematic differences. The difference between the observed up spectra at the two detectors will provide a precision measurement of the parameters involved in the up +) V, oscillations observed in atmospheric neutrinos. The Far Detector is a Steel/Scintillator sampling calorimeter, composed of 486 planes of 1” thick, 8m diameter steel octagons sandwiched with layers of 1 cm thick plastic scintillator. The steel provides target mass and passive calorimetry and the scintillator emits light at the passage of charged particles. The layers are hung perpendicular to the beam direction, making the complete detector 31 m long, 8 m in diameter, and 5.4 kt in mass. The steel will be magnetized by a 1.5 T field to provide charge discrimination. The layered structure provides good energy resolution for both penetrating and showering particles, and reliably distinguishes between the e, p, and x resulting from v interactions. The scintillator layers are composed of parallel, 4.1 cm wide, optically isolated strips. Light is channeled out of the plastic by wavelength shifting optical fiber, and carried from the edges of the detector by clear optical fiber to photomultiplier tubes (“PMT”s). *The poster
presenter gratefully acknowledges from the NSF through its RUI
O920-5632/03/$ - see front matter doi: 10.1016/SO920-5632(03)01363-X
support for grant #0098579
Q 2003 Elsevier
Science
this
B.\!
The fast timing of the scintillator light allows directional determination, and the experiment uses GPS timing to gate on the beam spill back at Fermilab. Construction began in August 2001. The first half of the detector is nearly completed, and when finished in July 2002 will be magnetized while the second half of the detector is assembled. Each of the planes is independently instrumented, allowing each plane to contribute to the data acquisition soon after it is physically installed. Although the NuMI beam will not turn on until the beginning of 2005, cosmic ray muons cross the detector at a rate of -lOOOp/strip/month. This is a great aid to the commissioning and calibration of the detector. Hardware problems are found and fixed quickly, and data acquisition and reconstruction software can be developed and tested on this real data. In particular, the problem of resolving the eight-fold ambiguity produced by multiplexing eight fibers to one PMT channel has been resolved. Taking advantage of the cosmic ray muons, which travel in straight lines at close to the speed of light, the geometry of the detector can be verified and the response calibrated. Channel-tochannel timing offsets are measured for later subtraction, and the timing resolution is found to be a 2.6 ns. The first atmospheric neutrino events have also been observed while looking through this collection of commissioning data. Two upward-going muon events have so far been recorded, although analyses of contained neutrino events are still being refined. This work ensures that when the NuMI beam is turned on, the MINOS Far Detector will be taking quality data from the very start. All rights
reserved.