About  Detectors

1. About  Detectors Alberto Marchionni, Fermilab • Next challenges in neutrino physics call for larger and specialized detectors • How to extrapolate from past & present neutrino detectors to what we need for the future ones ? • beam optimization (superbeams, off-axis,  factories,…) is a key element to simplify the detectors • not every detector technology of the past is fit for future applications • Water Cherenkov detectors • Sampling, tracking calorimeters • Liquid Argon TPC’s • Conclusions

2. The Physics Roadmap • The next generation of neutrino experiments will focus on  to e transitions to find out about • 13 • normal or inverted mass hierarchy • possibility of CP violation in the leptonic sector • We want to be sensitive to oscillation probabilities down to few10-3 • Experiments, at least in a first phase, will be statistics limited

3. Beam-Detector Interactions • At which distance and which energy ? • flux  1/L2 • oscillation probability  sin2(1.27 m2L/E) • Which energy ? 1st, 2nd,… oscillation maximum ? • dependence of  cross section on energy • sensitivity to matter effects • A limit: how many protons can I get ? • Neutrino beam optimization to reduce background • use a narrow energy beam (off-axis concept) to reduce NC background and beam e intrinsic background • use a neutrino factory and look for wrong sign muons • use of beta-beams • sensible choices will make the detector easier to build and operate

4. Different strategies m2=2.510-3 eV2 n=oscillation peak En < 1 GeV (KEK/JPARC to SuperK, CERN to Frejus 0.3 < En < 3 GeV (NuMI off-axis) 0.5< En < 5 GeV (C2GT, BNL to ?) • JPARC • mostly quasi-elastic, 1  • NuMI • few ’s, range out Different detectors 

5. Scaling violations Florence Dome, span 42 m, masonry structure Oita sports park “Big Eye” dome, span 274 m, steel structure Millennium Dome, Greenwich, London, span 365 m, cable structure

6. Super-Kamiokande 50,000 tonwater Cherenkov detector　(22.5 kton fiducial volume) 42 m 39 m

7. Hyper-Kamiokande Good for atm. n proton decay ~1,000 kt L=500 m 10 subdetectors Candidate site in Kamioka

8. MINOS Far Detector • 2 sections, each 15m long • 8m Octagonal Tracking Calorimeter • 486 layers of 2.54cm Fe • 4cm wide solid scintillator strips with WLS fiber readout • 25,800 m2 active detector planes • Magnet coil provides <B>  1.3T • 5.4kt total mass • Fully loaded cost ~$6 M/kton

9. MINOS Detector Technology Detector module with 20 scintillator strips MUX boxes route 8 (1 in Near Detector) fibers to one MAPMT pixel

10. energy e Interactions in MINOS? • Detector Granularity: • Longitudinal: 1.5X0 • Transverse: ~RM ne CC, Etot = 3 GeV NC interaction • NC interactions • energy distributed over a ‘large’ volume • e CC interactions (low y) • electromagnetic shower short and narrow • most of the energy in a narrow cluster

11. How to improve e signal/background: choice of the beam n spectrum NC (visible energy), no rejection ne background ne (|Ue3|2 = 0.01) NuMI low energy beam NuMI off-axis beam These neutrinos contribute to background, but not to the signal

12. A Detector for NuMI off-axis • Physics requirements • very large mass • identify with high efficiency e charged interactions • good energy resolution to reject e’s from background sources • e background has a broader energy spectrum than the potential signal • provide adequate rejection against  NC and CC backgrounds • e/0 separation • fine longitudinal segmentation, smaller than X0 • fine transverse segmentation, finer than the typical spatial separation of the 2 ’s from 0 decay • e/,h separation (electrons appears as “fuzzy” tracks) • optimized for the neutrino energy range of 1 to 3 GeV • detector on surface, must be able to handle raw rate and background from cosmic rays • fine granularity, low/medium Z tracking calorimeter

13. Towards a detector choice • Design challenges • large fiducial mass at low unit cost • aim to reduce the cost/kton by ~3 with respect to MINOS • fine granularity, low/medium Z tracking calorimeter • operating in a relatively remote location: rugged, robust, low level of upkeep and maintenance • A monolithic detector as tracking calorimeter ? • Large ( 10 kTon) LAr TPC, as evolution from the ICARUS design • A sampling detector as tracking calorimeter ? • several examples on a smaller scale in the past: CHARM, CHARMII, …. • choice of absorber structure and active detector modules

14. Detectors under consideration for NuMI off-axis • A sampling, tracking calorimeter detector of 50 kton • proposed absorber is manufactured wood sheets, either particleboard (from wood “sawdust”) or Oriented Strand Board (from wood chips) • structural strength • can be produced in sheets of sizes up to ~ 2.4m8.5m2.5cm • density ~ 0.7 g/cm3 • availability of industrial strength fastening systems, high strength adhesives, cartridge loaded screw guns,… • low cost: ~ $290/ton, production plants in Minnesota • proposed active detector elements • Liquid scintillator as the baseline technology • Glass Resistive Plate Chambers as backup

15. Liquid scintillator detector • 50 kton sampling calorimeter detector, comprised of 42 kton of wood particleboard as absorber and 7 kton of mineral-oil based liquid scintillator as active detector, contained in segmented PVC extrusions of 1 kton total mass • 1/3 X0 longitudinal granularity, 4 cm transverse granularity • made up of 750 planes, 29.3 m wide, 14.6 m high and 22.9 cm thick, arranged to provide alternating horizontal and vertical views, for a total length of 171.5 m • the liquid scintillator is contained in segmented titanium dioxide loaded PVC extrusions 14.6 m long, 1.2 m wide and 2.86 cm thick, with 4 cm transverse segmentation • the scintillation light in each cell will be collected by a looped 0.8 mm  wavelength-shifting plastic fiber • light from both ends of the fiber will be directed to a single pixel on an avalanche photodiode (APD) • 540,000 analog readout channels

16. Assembly of the liquid scintillator detector 29.3 m 48’ Stack: size 48’8’9” weight ~ 5 tons 8’ 14.6 m Each stack is equivalent to 7 layers of particle board and one layer of PVC extrusion containing liquid scintillator The detector consists of 750 planes. Each plane is made out of 12 stacks.

17. WLS fiber Emission spectra for L=0.5-16 m Hamamatsu 32-channel APD array Pixel size 1.81.8 mm2 Readout of the liquid scintillator detector The APD readout combines the advantages over PMT of lower cost and much higher quantum efficiency Manifold to collect fibers from the ends of scintillator cells to an optical connector Sizeable number of photoelectrons/MIP: ~30 photoelectrons for an interaction at the far end of a looped fiber. With FNAL SVX4 electronics and APD cooling expect S/N ~ 5:1

18. 19.5 m Aluminum end-frames 200 m 17.1 m Steel end-frames 5 planes of stacked modules • 50 kton detector made of 1200 modules, stacked in an array made of 75 planes along the beam direction, each plane being 2 modules wide and 8 high • Each module, 8.5m2.4m2.6m with a weight of 42 tons, consists of 12 vertical planes of absorber interleaved with a detector unit consisting of a double plane of RPC’s Glass RPC detector • Walls of modules are supported from the floor and are not connected to each other • Modules within each wall are interlocked with the help of corner blocks as used in standard shipping container

19. Glass RPC detector units • The low rate environment of a neutrino experiment makes it possible to use glass RPC’s with strip readout as active detectors • They can provide 2-dimensional position information from every plane of detectors • Very large induced signals processed by simple discriminators • measurement of the event limited to recording of “hits” • RPC chambers, 2.8442.425 m2, are composed of 2 parallel glass electrodes, 3 mm thick, kept 2 mm apart by Noryl spacers placed every 15 cm • 2 planes of RPC’s, each made of 3 RPC’s, are sandwiched between 2 particleboards, used as readout boards • Both surfaces of both particleboards are laminated with thin copper foil. Foils on inner surfaces are cut into strips • Each detector unit has 192 vertical strips and 64 horizontal ones • horizontal strips are 3.7 cm wide, vertical ones 4.34 cm wide • 3.7106 digital channels

20. Electron/ appearance RPC detector simulation Fuzzy track = electron Clean track = muon

21. NC background RPC detector simulation NC - 0 - 2 tracks gap

22. Simulation results • 41020 pot/yr, 5 year run • 50 kton RPC detector, 85% fiducial mass • positioned at a distance=735 km, offset=10 km • m2=2.510-3, sin2(213)=0.1, no matter effects or CP included • Figure of merit: S/B=214.5/49.6=30.4

23. light Ionizing Track Drifting e- ICARUS: a Liquid Argon Imaging Detector • Working principle: • Ionization chamber filled with LAr, equipped with sophisticated electronic read-out system (TPC) for 3D imaging reconstruction, calorimetric measurement, particle ID. • Absolute timing definition and internal trigger from LAr scintillation light detection A. Rubbia

24. Neutrino physics with a Large LArTPC • The ideal detector for a neutrino factory/off-axis a’ la NuMI • Excellent pattern recognition capabilities and energy determination • High efficiency for electron identification and excellent e/0 rejection •  identification via kinematic reconstruction • lepton charge determination if in a magnetic field

25. ICARUS T300 Prototype LAr Cryostat (half-module) View of the inner detector 4 m 4 m 20 m

26. Coil Iron yoke Field shaping electrodes Cathode Cryostat Wire chamber A large magnetized LAr TPC LANNDD: Liquid Argon Neutrino and Nucleon Decay Detector F. Sergiampietri, NuFact’01 • = 40 m H = 40 m 85 m drifts 70 kTon active LAr mass

27. Detector chambers structure F. Sergiampietri, NuFact’01 • # wire chambers: 4 • CH1,CH4 W=26.8 m, H=40 m • CH2,CH3 W=39.2m, H=40 m • readout planes/chamber: 4 • 2 @ 0o, 2 @ 90o • stainless steel 100m wires at a 3 mm pitch • screen-grid planes/chamber: 3 • total # wires (channels): 194648 • # cathode planes: 5

28. R&D on a Large LAr TPC • R&D items to face • Engineering of a large cryostat • Engineering of wire chambers • HV feedthroughs up to 250 kV • Argon purity • Working conditions under high hydrostatic pressure HV=200-250 kV Tmax drift=3.1-3.6 ms

29. My personal conclusions • Different “baselines & energies” have different detector requirements • given the importance of the physics measurements, which could possibly lead to the discovery of CP violation in the leptonic sector, measurements with different detectors are important and different baselines are somewhat complementary • Water Cherenkov detectors are a well established technology • a factor 20 increase in mass is being considered • A large effort is underway to develop large (~50 kton) sampling, tracking calorimeters • R&D is crucial to verify the choice of technology • Impressive results from ICARUS 300 ton prototype • LAr technology is mature to proceed with the construction of a few kton detector • LAr technology could be considered for 10 kton detector • Lots of room for new, clever ideas, … but we need to move up to be ready to fully exploit the facilities that we have now • we are in the lucky situation where a series of upgrades in beamlines/detectors could lead us to important physics discoveries