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How to Build a Neutrino Oscillations Detector Why MINOS is like it is! Alfons Weber March 2005 Neutrino Oscillations • MINOS is a long baseline Neutrino Oscillation Experiment – – – What do we want to measure? We want to see, how one type of Neutrino transforms itself into another. There is a characteristic pattern, if this is transformation is due to “neutrino mass eigenstates” 1 , 2 • or Simplified two neutrino scenario: cos sin March 2005 A. Weber sin 1 cos 2 1.27m2 L P( ) 1 sin (2 )sin E 2 MINOS Experiment 2 2 March 2005 A. Weber MINOS Experiment 3 NuMI & The Main Injector Fermilab Main Injector: 120 GeV protons 2.5 x 1013 protons/pulse 1.9 sec rep rate (~8 sec spill) 0.25 MW NuMI Beam: Graphite target Two magnetic horns 675 m. vac. decay pipe hadron absorber designed for 4 x 1013 ppp Beam Monitoring: muon detectors hadron detectors + Near Detector ! March 2005 A. Weber MINOS Experiment 4 NuMI Beam Layout March 2005 A. Weber MINOS Experiment 5 Neutrino Production 120 GeV primary Main Injector beam Target readily movable in beam direction 2-horn beam adjusts for variable energy ranges 675 meter decay pipe for p decay March 2005 A. Weber MINOS Experiment 6 MINOS Physics Reach Intense beam from FNAL Nominal Beam Configurations - initially 2.5 x 1020 p.o.t./year, (being commisioned now !!) νµ CC Events/year (with no oscillations) Low Medium High 1,600 4300 9250 Beam spectra: M. Messier March 2005 A. Weber MINOS Experiment 7 Neutrino Interactions • Charge current – – – – electron νμ muon tau Can measure neutrino energy hadrons μ 5m • Neutral Current – electron – muon – tau νμ hadrons νμ 1.5 m March 2005 A. Weber MINOS Experiment 8 Oscillation Pattern 1.27m2 L P( ) 1 sin (2 )sin E 2 m 2 2 E L m 2 3 103 eV 2 measures m2 No Effect! Smeared by resolution P ~ 1/2 March 2005 L 735 km A. Weber MINOS Experiment 9 MINOS Analysis • Select νμ charge current events and reconstruct neutrino energy E E Eh range, B field calorimetric Energy resolution: p / p 10% Eh / Eh 60% / E Compare energy spectrum in near and far detector Measure Δm2 and sin22θ • Look for appearance of νe Δm2 sin22θ beam & NC contamination March 2005 A. Weber MINOS Experiment 10 Where should the Experiment be? • Δm2= 0.002-0.003 eV2 (from SK) • In oscillation Minimum L/E = 400 - 800 km / GeV • Larger distance shorter distance • High energy low energy • Flux ~ 1/L2 • Cross section ~ E • Event size ~ E March 2005 A. Weber MINOS Experiment 11 The MINOS Experiment • NuMI beam travels 735 km to Soudan (MN) • Sagitta:10 km • 1 km wide at destination March 2005 A. Weber MINOS Experiment 12 March 2005 A. Weber MINOS Experiment 13 Detector • Design requirements – High Mass – High segmentation – Affordable March 2005 A. Weber MINOS Experiment 14 MINOS Detectors • There are 3 MINOS Detectors – Near Detector – Far Detector – Calibration Detector @ FNAL @ Soudan @ CERN (ND) (FD) (CalDet) • Magnetised steel scintillator tracking calorimeter – Alternating planes of steel and scintillator strips 5.4 kton March 2005 A. Weber MINOS Experiment 0.9 kton 12 ton 15 Soudan Underground Laboratory • former iron mine, now a state park, – home of: Soudan-1 & 2 , CDMS-II , and MINOS expts March 2005 A. Weber MINOS Experiment 16 MINOS Construction Challenge March 2005 A. Weber MINOS Experiment 17 MINOS Plane 2-m wide, 0.5-inch thick steel plates Bottom steel plane layer Scintillator plane Top steel plane layer o Orientations alternate 90 in successive planes March 2005 A. Weber MINOS Experiment 18 Far Detector • In old iron mine • Was already there – Soudan 1 & 2 • Right distance from FNAL March 2005 A. Weber MINOS Experiment 19 MINOS Scintillator Module 8m Optical Connector Connection to electronics Connection to electronics Optical Connector Optical Connector Multiplex Box Optical Connector Multiplex Box Clear Fiber Ribbon Cable (2-6 m) WLS Fibers WLS Fibers Scintillator Module • 4-8m scintillator modules • 24-28 strips • double sided readout • multi anode PMTs (16/64) PMTs March 2005 A. Weber MINOS Experiment 20 PMT • Light is detected by multi-anode PMTs – 230x – 1500x 64-pixel in ND 16-pixel in FD • pixel to pixel variations March 2005 A. Weber MINOS Experiment 21 FD Front End Electronics • MINOS developed an ASIC chip for PMT readout – – – – – 32 channels shaping amplification sample & hold output driver to ADC • Excellent product – – – – fast shaping 500 nsec noise < 2 fC linear> 20 pC 6 ASICs multiplexed onto 1 ADC March 2005 A. Weber MINOS Experiment 22 Signal Amplification March 2005 A. Weber MINOS Experiment 23 Output of Pre-amplifier March 2005 A. Weber MINOS Experiment 24 Signal Digitisation March 2005 A. Weber MINOS Experiment 25 DAQ System • Trigger-less DAQ system – – – – PMTs • Timing System ASIC close to PMT – Absolute time from GPS (tabs= 200 nsec) ADC in VME crate – optical distribute along fast PVIC-bus to PC trigger farm large detector (trel= 4 nsec) search for hits correlated in space and time 2 1 0 2 1 0 HV VFB 2 1 0 HV VFB VFB VARC 2 VARC 1 VARC 0 VARC 1 VARC 2 VME Readout Crates ROP serial PVIC Ether. HV VFB 2.5 MB/s DAQ LAN ROP serial PVIC Ether. TRC 3 2 1 0 Optical PVIC Bus RC B B B B R R R R P P P P Timestamp Clock 1 sec GPS ticks antenna GPS Timing Central unit Timing PC Timing System March 2005 A. Weber DAQ LAN 0 3 15 VARC 0 VME VME TRC 2 1 0 HV Front End Electronics DAQ LAN 40 Mbytes/s PVIC Bus DAQ LAN DAQ LAN DCP To Persistent Store To Dispatcher Branch Readout Processors TP TP TP N 1 0 Trigger Processors 10-100 Kbytes/s MINOS Experiment 26 Near Detector Event Low-energy track from fiducial region MINOS Preliminary Etrack approx. 1.5 GeV March 2005 A. Weber MINOS Experiment 27 Additional Near Detector Events Medium energy track from near peak in “pseudo-medium” beam MINOS Preliminary Etrack approx. 3.1 GeV March 2005 A. Weber MINOS Experiment 28 Additional Near Detector Events One “snarl” (beam pulse) in near detector, showing multiple events. MINOS Preliminary March 2005 A. Weber MINOS Experiment 29