About DetectorsAlberto 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

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 few10-3

Experiments, at least in a first phase, will be statistics limited

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

Different strategies

L(km)/n1

(GeV)

2

(GeV)

3

(GeV)

300 0.61 0.20 0.12

800 1.62 0.54 0.32

1200 2.43 0.81 0.49

E < 1 GeV (KEK/JPARC to SuperK, CERN to Frejus0.3 < E < 3 GeV (NuMI off-axis)0.5< E < 5 GeV (C2GT, BNL to ?)

n=oscillation peak

m2=2.510-3 eV2

JPARC• mostly quasi-elastic, 1

NuMI• few ’s, range out

Different detectors

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

Super-Kamiokande

39 m

42 m

50,000 ton water Cherenkov detector (22.5 kton fiducial volume)

Hyper-Kamiokande

~1,000 kt

Candidate site in Kamioka

Good for atm. proton decay

L=500 m10 subdetectors

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

MINOS Detector TechnologyDetector module with 20 scintillator strips

MUX boxes route 8 (1 in Near Detector) fibers to one MAPMT pixel

e Interactions in MINOS?

e CC, Etot = 3 GeV

energy

Detector Granularity:

•Longitudinal: 1.5X0

•Transverse: ~RM

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

How to improve e signal/background: choice of the

beam

NuMI off-axis beam

NuMI low energy beam

These neutrinos contribute to background, but not to the signal

spectrum NC (visible

energy), no rejection

e background

e (|Ue3|2 = 0.01)

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

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

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 ~ 2.4m8.5m2.5cm• 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

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

Assembly of the liquid scintillator

detector

Each stack is equivalent to 7 layers of particle board and one layer of PVC extrusion containing liquid scintillator

Stack: size 48’8’9” weight ~ 5 tons

The detector consists of 750 planes. Each plane is made out of 12 stacks.

48’

8’

29.3 m

14.6

m

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

0

0.2

0.4

0.6

0.8

1

450 500 550 600 650

Wavelength (nm)

Qu

an

tum

eff

icie

nc

y

APD

PMT

w

WLS fiber Emission spectra for L=0.5-16 m

Hamamatsu 32-channel APD array

Pixel size1.81.8 mm2

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

5 planes of stacked modules

17.1 m

19.5

m

200 mAluminum end-frames

Steel end-frames

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, 8.5m2.4m2.6m 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

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

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, 2.8442.425 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

3.7106 digital channels

Fuzzy track = electron

Clean track = muon

Electron/ appearanceRPC detector simulation

NC - 0 - 2 tracks

NC background

RPC detector simulation

gap

Simulation results 41020 pot/yr, 5 year run 50 kton RPC detector, 85% fiducial mass positioned at a distance=735 km, offset=10 km m2=2.510-3, sin2(213)=0.1, no matter effects or CP included

Signal Backgrounds

Beam e

NC CC

Reconstructed events before

cuts

639.4 477.2 6899.8 10110.7

After cuts 214.5 24.6 21.9 3.1

Efficiency/Bckgfraction

33.5% 5.210-

2

3.210-

3

3.110-4

Figure of merit: S/B=214.5/49.6=30.4

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

Drifting

Ionizing Track

e-

light

A. Rubbia

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

LAr Cryostat (half-module)

20 m

4 m

4 m

View of the inner detector

ICARUS T300 Prototype

Iron yoke

Coil

Cryostat

Field shapingelectrodes

Wire chamber

Cathode

A large magnetized LAr TPCLANNDD: Liquid Argon Neutrino and Nucleon Decay Detector

F. Sergiampietri, NuFact’01

= 40 mH = 40 m85 m drifts70 kTon active LAr mass

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 100m wires at a 3 mm pitch• screen-grid planes/chamber: 3

total # wires (channels): 194648 # cathode planes: 5

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 kVTmax drift=3.1-3.6 ms

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