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 TPCs
• 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
?m22.5?10-3 eV2
noscillation peak
En lt 1 GeV (KEK/JPARC to SuperK, CERN to Frejus
0.3 lt En lt 3 GeV (NuMI off-axis)
0.5lt En lt 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 ton water Cherenkov detector (22.5 kton
fiducial volume)
42 m
39 m
7
Hyper-Kamiokande
Good for atm. n proton decay
1,000 kt
L500 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 ltBgt ? 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
?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 (Ue32 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 ?es 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
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 51
18
Glass RPC detector

• 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 RPCs

• 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 RPCs
  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 RPCs, each made of 3 RPCs, 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 distance735 km, offset10 km
• ?m22.5?10-3, sin2(2?13)0.1, no matter effects
  or CP included

• Figure of merit S/?B214.5/?49.630.4

23
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
20 m
4 m
26
A large magnetized LAr TPC
LANNDD Liquid Argon Neutrino and Nucleon Decay
Detector
F. Sergiampietri, NuFact01

• 40 m
• H 40 m
• 8?5 m drifts
• 70 kTon active LAr mass

27
Detector chambers structure
F. Sergiampietri, NuFact01

• wire chambers 4
• CH1,CH4 W26.8 m, H40 m
• CH2,CH3 W39.2m, H40 m
• readout planes/chamber 4
• 2 _at_ 0o, 2 _at_ 90o
• stainless steel 100?m wires at a 3 mm pitch
• screen-grid planes/chamber 3
• total wires (channels) 194648
• cathode planes 5

28
RD on a Large LAr TPC

• RD 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

HV200-250 kV Tmax drift3.1-3.6 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
• RD 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