Scintillation + Photo · PDF filemolecules osmall fraction of energy released as ... NIM A...
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Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/1
Scintillation + Photo Detection
Inorganic scintillators
Organic scintillator
Readout & fiber tracking
Photo detectors
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/2
Scintillation
Scintillation
Two material types: Inorganic & organic scintillators
(generally)high light output lower light output
but slow but fast
photodetector
Energy deposition by ionizing particle excitedmolecules small fraction of energy released asoptical photons (scintillation light or luminescense)
Scintillators multi purpose detectors
calorimetrytime of flight measurementtracking detectors (fibers)trigger countersveto counters…..
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/3
Inorganic scintillators
3 different scintillation mechanisms:1a. Inorganic crystalline scintillators (NaI, CsI, BaF2...)most common: sodium iodide with thallium trace [NaI(Tl)]
due to high density& high Z inorganicscintillators well suitedfor charged particle &photon detection.
light output ofinorganicscintillatorswavelengthdependent
energy bandsin crystalsactivated byimpurity tracesoften 2 timeconstants:• fast recombi-nation (10 ns -1 s) from acti-vation centers• delayedrecombinationdue to trapping( 100 ms)
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/4
Inorganic scintillators
Light output of inorganic crystals also shows strongtemperature dependence
1b. Liquid noble gases (LAr, LXe, LKr)
A
A+
A2*
A2+
A
A
e-
ionization
collisionwith g.s.atoms
excitedmolecule
ionizedmolecule
de-excitation anddissociation
UV130nm (Ar)150nm (Kr)175nm (Xe)
A*excitation
A2*
recombination
also here one finds 2 time constants: one at few ns &a second at 10 1000 ns but both at same wavelength.
BGO
PbWO4
(From Harshaw catalog)
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/5
Inorganic scintillators
LAr 1.4 1.295)120-1705 / 860LKr 2.41 1.405)120-170LXe 3.06 1.605)120-170
5) at 170 nm2 / 853 / 22 1.00
14
2.87
A lead tungstate(PbWO4) crystal forCMS electromagneticcalorimeter (goodradiation tolerance &high density ataffordable cost)
Light yield normalized to NaI(Tl) 40k photons / MeVNB! light output dependent on light collection efficiency &quantum efficiency of photo detector (see following pages)
sensitive to humidity?
wavelength of maximum emissionProperties of some inorganic crystal scintillators
for a MIP
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/6
Organic scintillators
Scintillation basedon the twoelectrons of theC C bonds(“aromatic rings”).
Organic scintillators have low Z (H,C) low photondetection efficiency but high neutron efficiency via(n,p) reactions. Reasonable for charged particles.
2. Organic scintillators: liquid or plastic solutionsoriginal emitted light in UV range
Normally made of plastic base/solvent & primary fluor+ secondary (& tertiary) fluors as wavelength shifters.Fast energy transfer from plastic base/solvent to fluorsvia resonant dipole-dipole interactions (”Förstertransfer”) since short distances between molecules
shift emission to longer wavelengthslonger absorption length & more efficient read-out
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/7
Organic scintillators
Some widely used plastic bases/solvents & fluors:
After mixing components together plastic scintillatorsproduced by a complex polymerization method.Very easy to shape.
Most organic scintillators have similar properties:density ( ) 1.03 – 1.20 g/cm3
refractive index (nD) 1.58decay time ( decay) 1-12 nslight yield 10k photons / MeV (25 % of NaI(Tl))
plastic base/solvent primary fluor secondary fluorLiquidscintillators
TolueneXylene
DPOPBD
BBOBPO
Plasticscintillators
PolyvinyltoluenePolystyrene
DPOPBD
TBPBBODPS
Schematicrepresentationof wave lengthshiftingprinciple
(C. Zorn,Instrumentation In HighEnergy Physics, World
Scientific,1992)
DPO = diphenyloxazolePBD = phenyl-biphenylyloxadizole
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/8
Scintillator readout
Scintillator readoutReadout to be adapted to geometry & emissionspectrum of scintillator (need to shift wavelength?).Geometrical adaptation:
optical fibers & light guides: light transport by totalinternal reflection (& outer reflector for light guides)
wavelength shifter (WLS) bars
Photo detector
primary particle
UV (primary)
blue (secondary)
greensmall air gap
scintillator
WLS
adiabatic light guide
optical fiber
corepolystyrene
n=1.59
cladding(PMMA)n=1.49
25 m
fluorinatedouter claddingn=1.42
25 m
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/9
Scintillating fiber tracking
Scintillating fiber trackingScintillating plastic fibersCapillary fibers, filled with liquid scintillatorHigh geometrical flexibility & low massFine granularity & good hermeticity (=“no holes”)Fast response (ns) (if fast read out) 1st level trigger
60 m
Hexagonal fibers with double cladding. In figure onlycentral fiber illuminated low cross talk !
3.4 m
Number of photonsproduced by atraversing minimumionizing particle notvery high so needefficient readout.1 mm fiber< 2000 photons.Taking into accountfiber attenuation,capturing & photodetector efficiency10 20 photons remain (must
be careful not to loose signal).
D0 central tracker at Tevatron:1.6 -2.5 mlongpolysterenefibers.
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/10
Photo Detectors
purpose: convert light into detectable electronics signalprinciple: Use photoelectric Effect to convert photonsto photo electrons (multiplied by some mechanism)
standard requirementhigh sensitivity, usually expressed asquantum efficiency Q.E. = Nphoto electrons / Nphotons
Main types of photo detectorsgas based (use photosensitive additive e.g. TMAE)vacuum based (photosensitive photo cathode)solid state detectors (e.g. GaAs)
Photoemission threshold Wph of various materials
100 250 400 550 700 850 [nm]
12.3 4.9 3.1 2.24 1.76 1.45 E [eV]
VisibleUltraViolet(UV)
Multialkali
Bialkali
GaAs
TEA
TMAE,CsI
InfraRed(IR)
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/11
Photo Detectors
Photo Multiplier Tube (PMT)
main phenomena:• photo emission from
photo cathode.• secondary emission
from dynodes.dynode gain: g = 3 50
total gain:
For example: 10 dynodeswith g = 4 M = 410 106
N
iigM
1
PMT’s very sensitive tomagnetic fields, even toearth field (30-60 T).metal shielding required.
(Philips Photonic)
e
photon
Photoelectric effect in photo cathode 3-step process:- absorbed ’s give energy to e’s in photo cathode (PC)- e’s diffuse through PC, losing part of their energy- e’s reaching surface with enough excess energy escapeideal photo cathode absorb all ’s & emit all created e’semission threshold Wph > Eg (band gap) + Ea (electron affinity)
Photo cathode:Multialkali: SbNa2KCsBialkali: SbKCs, SbRbCs
quartz
dynode: Ag/Mg, Cu/Beor Cs/Sb
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/12
Quantum efficiencies of typical photo cathodes
Photo Detectors
Energy resolution of PM’s: determined by fluctuations ofthe number of secondary electrons emitted by dynodes(follows a Poisson distribution with expectation value ).
Relative resolution:nn
nn
n 1 (fluctuations atthe first dynodemost important!!)
n
up to 8x8 channels.size: 28x28 mm2.active area 18x18 mm2 (41%).bialkali PC: Q.E. = 20% at
max = 400 nm. Gain 106.
Multi anode PM´s e.g Hamamatsu R5900 series
(Hamamatsu)
GaAsP GaAs
CsTe(solarblind)
MultialkaliBialkali
Ag-O-Cs
Photon energy E (eV)12.3 3.1 1.76 1.13
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/13
Photo Detectors/Large area applications
Hybrid photo diodes (HPD) – large window inwave length for photon acceptance
Photo cathode likein PMT, V = 10 20 kV
31056.3
20eV
keVW
VeGSi
V
photocathode
focusingelectrodes
siliconsensor
electron
photo electronacceleration + silicondetector (pixels or strips)
(LHCb - DEP)
Pixel-HPD, 80mm Øcross-focused
3 x 61 pixels
test beam data, 3 HPDs
Cherenkov ring imaging with HPD’s
can do real singlephoton counting !!Q.E. 10 - 30 %
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/14
Photo Detectors/Small area applications
Visible Light Photo Counter (VLPC)
vacuum tube
photo cathode
anode (grid)
dynode
40 m
m
G 7 10. Work in axialmagnetic fields of 1 TUsed by OPAL & DELPHIfor readout of lead glassendcap calorimeters.
High reverse biasvoltage 100 200 V.High internal fieldavalanche multiplication.G 100 107
Q.E. 70 %sub-ns response time
(sketches from J.P. Pansart, NIM A 387 (1997), 186)Avalanche Photo Diodes (APD)
Photo triodes = single stage PMT
•-•+Photon
IntrinsicRegion
GainRegion
SubstrateDriftRegion Spacer
Region
Hole drifts towardshighly doped driftregion & ionizes adonor atom freeelectron. Multiplicationby ionization of furtherneutral donor atoms.
•h•e•e
• Operation at low bias voltage (7 V)• High infrared sensitivity requires liquid He cooling• Q.E. upto 90% in a small wavelength range (500-600 nm).• Gain up to 50.000 but also noise prone system!
IEEE NS-30 No. 1 (1983) 479
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/15
Basic principlesInteraction of chargedparticles & photonsElectromagnetic cascadesNuclear interactionsHadronic cascades
Homogeneous calorimetersSampling calorimeters
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/16
Calorimetry
Calorimetry:Energy measurement by total absorption,combined with spatial reconstruction.
Calorimetry a “destructive” method
Detector response (ideally) E
Calorimetry works both forcharged (e & charged hadrons)neutral particles (neutral hadrons, )
Basic mechanism: formation ofelectromagnetic showers (e , & 0’s)hadronic showers (charged & neutral hadrons)
In the end, all energy converted intoionization or excitation of detector material.
An electromagnetic part to measure e , & 0’s& an hadronic part to measure all other particles
”only” measurement of neutrals
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/17
Interaction of charged particles
Z,A
chargedparticle
Energy loss by Bremsstrahlung
Emission of real photonsby a charged particleaccelerated in Coulombfield of nuclei of absorber
Effectively plays a role only for e± & ultra-relativistic ’sFor electrons:
Taking also into account the interactions with theatomic electrons ( Z)
EZdxdENB
Ioniz
ln!
3/122
220
23 183ln)(
)(4Z
EznZcm
cdxdE
e
)/183ln(4
)/183ln(4
3122
0
0
312
2
ZrZN
AX
XE
dxdE
ZErA
ZNdxdE
eA
eA
)/287ln()1(4.716
0 ZZZAX
radiationlength
[g/cm 2]
(>1 TeV)
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/18
Interaction of charged particles
(Leo)
Radiation length of material defined for electrons !!
For a compound:
Critical energy Ec
For electrons one finds approximately:
For example Ec(e ) in Fe (Z=26) = 22.4 MeVFor muons:
Ec( ) in Fe (Z=26) 1 TeV
bremsstrahlung need only be taken into account for e !!
N
jjj
Xw
X 1 00
1 wj: mass fractionof components
energy loss(bremsstrahlung+ ionization) ofelectrons &protons in copper
Ionizc
Bremsc E
dxdEE
dxdE
92.0710
24.1610 gasliquidssolid
ZMeVE
ZMeVE cc
2
)()(e
cc mm
eEE
Ec
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/19
Interaction of photons
Interaction of photonsTo be detected, a photon has to create chargedparticles and/or transfer energy to charged particles(note photon interaction with matter fundamentallydifferent w.r.t. charged particles since photonseither absorbed or large angle scattered)
3 mechanisms: photo-electric effect, Comptonscattering & pair production
• Photo-electric effect:
Only possible in close neighborhood of a third collisionpartner (the nucleus) photo effect releases mainlyelectrons from the K shell ( 80 %).
cross section shows strong modulation when EEionization
shell. At high energies ( 1)
e-
X+X
eatomatom
)Thomson(32 238
254
7
21
eeTh
e
eTh
Kphoto r
cmE
Z
14 542 ZreKphoto
5Zphoto
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/20
Interaction of photons
independentof energy !
• Compton scattering:
Assume electron as quasi-freecross section: Klein-Nishina formula, at high energies:
atomic Compton cross-section:
• Pair production
Only possible in Coulombfield of a nucleus (or an e ) if
cross section (high energy approximation)
'' ee
cos111EE
)2ln( 21
2ee
cr
ec
atomicc Z
Z
e+
e-nucleuseenucleus
22 2cmE e
At high energiesenergy sharingbetween e+ & emore asymmetric.
31
183ln974 22
ZZrepair
00 7
9197 X
XNA
pairA
the interaction length for photons
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/21
Interaction of photons
...)or( )(
00
PairComptonPhoto
Xx xXeIeIxXI
: massattenuationcoefficient
Comptonscattering
Pairproduction
Photo-electriceffect
4M
eV
In summary for photon interactions with matter: (todescribe the statistical process of photon attenuation):
: linearabsorptioncoefficient
gcmA
Ni
A
i
i 2
(Grupen)
(Kleinknecht)
Dominating effectin each domain ofthe photon energy
atom number Zof absorber plane
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/22
Reminder: basic electromagnetic interactionse+ / e
Photoelectric effect
Compton effect
Pair production
Ionisation
BremsstrahlungE
dE/d
x
E
dE/d
x
E
E
E
Electronshower in a
cloud chamberwith leadabsorbers
A real electromagnetic shower:
NB!
fore
ener
gylo
ss
NB!
for
inte
ract
ion
prob
abili
ty
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/23
Electromagnetic cascades
2lnln 0
maxcEEt
c
t
t
tttotal
EEN 0
0
)1( 2122max
max
process continues until E(t) < Ec
after t = tmax dominating processes ionization,excitation,Compton scattering & photo-electric effect absorption.
Simple qualitative model
e±
consider onlybremsstrahlung& pair production(OK for highenergy e/ ).for simplicity:X0 pair & e 2
t(max): shower depthin radiation lengths(at maximal numberof shower particles)
ttN 2)(tEtE 2/particle)( 0
em
em
em
emem
t = # of X0 or pair
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/24
Electromagnetic cascades
Longitudinal shower development:
98% energy containmentsize of a calorimeter grows only logarithmically with E0
max%98 5.2 tt
Example: 60 GeV electron in leadglass, Ec = 11.8 MeV tmax 8.0,t98% 20.0; X0 2 cm, RM 3.6 cm
][MeV210 cmX
ER
cM
Transverse development of electromagnetic shower(mainly caused by multiple scattering of electrons &positrons with detector material): cone containing 90(95) % of the shower energy has a radius of 1(2) RM
Molière radius
40 cm
14 cm
(Ce = 0.5;C = +0.5)
(PDG)
jc
CEEt 0em
max ln
showermaximum(in reality) at
em
em
btetEdtdE )( em
0
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/25
Energy resolution
Energy resolution of a calorimeter (intrinsic limit)
c
total
EEN 0 total number of track segments
0
11)()(ENN
NEE
Ecb
Ea
EE)(
holds also forhadron calorimeters
stochastic termdepends onthe number ofcreatedsecondary tracksegments
More general:
constant term
inhomogenities,bad cell inter-calibration,non-linearities
noise term
electronic noise,radioactivity,pile up
quality factor !!
also spatial and angular resolution scale like 1/ E
calorimeters relative energyresolution improves with E0 !!
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/26
Nuclear InteractionsThe interaction of energetic hadrons (charged/neutral)determined by inelastic (& elastic) nuclear processes.
For high energies (> 1 GeV) the cross-sectionsdepend only little on the energy & on the type of theincident particle (p, , K…).
In analogy to radiation length X0 a hadronicinteraction length can be defined (inelastic only)
similarly a hadronic collision length (inelastic + elastic)
Nuclear interactions
n
p
+
0
-
hadronZ,A
7.00
3.0 since AAN
Ainel
inelAI
mbAinel 3507.0
0
secondary multiplicity ln(E)
Inelastic: excitation & finally breakup of nucleusnuclear fragments + production of secondary particles.
IctotalA
c AN
A31
transverse size: pt had 0.4 GeV
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/27
Nuclear interactions
Material Z A [g/cm3] X0 [g/cm2] I [g/cm2]
Hydrogen (gas) 1 1.01 0.0899 (g/l) 63 50.8Helium (gas) 2 4.00 0.1786 (g/l) 94 65.1Beryllium 4 9.01 1.848 65.19 75.2Carbon 6 12.01 2.265 43 86.3Nitrogen (gas) 7 14.01 1.25 (g/l) 38 87.8Oxygen (gas) 8 16.00 1.428 (g/l) 34 91.0Aluminium 13 26.98 2.7 24 106.4Silicon 14 28.09 2.33 22 106.0Iron 26 55.85 7.87 13.9 131.9Copper 29 63.55 8.96 12.9 134.9Tungsten 74 183.85 19.3 6.8 185.0Lead 82 207.19 11.35 6.4 194.0Uranium 92 238.03 18.95 6.0 199.0
0.1
1
10
100
0 10 20 30 40 50 60 70 80 90 100
X0
I
X 0,
I[c
m]
Z
For Z > 6: I > X0
I and X0 in cm
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/28
Interaction of neutrons and neutrinos
dA
NN Adet
Interaction of neutrinosNeutrinos interact only weakly tiny cross-sectionsFor their detection we need again charged particles.Possible detection reactions:
• + n + p = e, ,• + p + n = e, ,
Cross-section for the reaction e + n e + p is of theorder of 10 43 cm2 (per nucleon, E few MeV).
Detection efficiency
1 m Iron:Neutrino detection requires very (!!) big detectors(“light year size”) or big & massive detectors (ktons) +very high neutrino fluxes (“long beam line experiments”).Event rates typically low (~ 10) e.g. SN1987a detectedby Kamiokande experiment with handful of events.
In collider experiments fully hermetic detectors allowto detect neutrinos indirectly:• sum up all visible energy & momentum.• attribute missing energy & momentum to neutrino.example UA1: W+ e+ + e. Reconstruct transversemomentum of the e from missing transversemomentum of the whole event (“missing ET & pT”).
17det 105
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/29
Hadronic cascades
Hadronic cascades (showers)
hadronic + electromagneticcomponent
some energy of shower lost due to neutrinos, muons …
large energy fluctuations limited energy resolution
neutral pions ( 2 , electrons, ’selectromagnetic cascade
visible energy
charged hadrons: pions, protons, kaonsneutral hadrons: neutrons, neutral kaons
visible energy
Various processes involved. Much more complexthan electromagnetic cascades.
(Grupen)
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/30
Hadronic showers and instrumental effects
longitudinal shower development
]cm[ln7.0][ln2.0)(
%95
max
bEatGeVEt I
for iron: a = 9.4, b = 39E = 100 GeV
t95% 80 cm
Iron: I =16.7 cm
Hadronic showers are much longer and broader thanelectromagnetic ones !
(B. Friend et al., NIMA136 (1976) 505)Laterally shower consists
of core + halo. 95%containment in acylinder of radius I.
OPAL end cap pre-shower + calorimeter
(C. Beard et al., NIM A 286 (1990) 117)
had
had
had
Material in front of calorimeterShowers start in ‘dead’ material in front of calorimeter(other detectors, solenoid, support structure)Install a highly segmented pre-shower detector in frontof calorimeter- recover lost energy- improved background rejectiondue to better spatial resolution
- improve angular resolution
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/31
Calorimetry
Calorimeter types
Homogeneous calorimeters:
Sampling calorimeters:
detector = absorbergood energy resolutionlimited spatial resolution (particularly in
longitudinal direction)only used for electromagnetic calorimetry
detectors & absorber separated onlyfraction of the energy measured.
limited energy resolution
good spatial resolution
used both for electromagnetic & hadronic
calorimetry
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/32
Homogeneous calorimeters
Homogeneous calorimeterstwo main types: scintillator crystals or “glass” blocks
(that use Cherenkov radiation, see later).photons. readout via photomultiplier, -diode/triode
scintillators (crystals)
Cherenkov radiators
Scintillator Density[g/cm3]
X0 [cm] LightYield/MeV
(rel. yield)
1 [ns] 1 [nm] Rad.Dam.[Gy]
Comments
NaI (Tl) 3.67 2.59 4 104 230 415 10 hydroscopic,fragile
CsI (Tl) 4.51 1.86 5 104
(0.49)1005 565 10 Slightly
hygroscopicCSI pure 4.51 1.86 4 104
(0.04)10 31036 310
103 Slightlyhygroscopic
BaF2 4.87 2.03 104
(0.13)0.6 220620 310
105
BGO 7.13 1.13 8 103 300 480 10PbW04 8.28 0.89 100 10 440
10 530104 light yield =f(T)
Material Density[g/cm3]
X0 [cm] n Light yield[p.e./GeV](rel. p.e.)
cut [nm] Rad.Dam.[Gy]
Comments
SF-5Lead glass
4.08 2.54 1.67 102
SF-6Lead glass
5.20 1.69 1.81 102
PbF2 7.66 0.95 1.82 2000 103 Not availablein quantity
Relative light yield: rel. to NaI(Tl) readout with PM (bialkali PC)
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/33
Homogeneous calorimeters
examplesOPAL Barrel + end-cap: lead glass + pre-sampler
BGO E.M. Calorimeter in L3
10500 blocks (10 x10 x 37 cm3, 24.6 X0),photo multiplier(barrel) or photo triode(end-cap) readout.
002.006.0)( EEE
(OPAL collab. NIM A 305 (1991) 275)
11000 crystals, 21.4 X0,temperature monitoring +control system, lightoutput very sensitive totemperature (-1.55 %/ C)
E/E < 1% for E > 1 GeVspatial resolution < 2 mm
(E >2 GeV)
(L3 collab. NIM A 289 (1991) 53)
Spatial resolution(intrinsic) 11 mmat 6 GeV
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/34
Sampling calorimeters
Sampling calorimetersabsorber + detector separated additional samplingfluctuations
d e te c to rs a b s o rb e rs
d
dX
EEF
dTN
c
10
det detectable track segments
0
1Xd
ENN
EE
• MWPC, streamer tubes• warm liquids
TMP = tetramethylpentane,TMS = tetramethylsilane
• cryogenic noble gases:mainly LAr (LXe, LKr)
• scintillators, scintillation fibers, silicondetectors
”gain”factor
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/35
Sampling calorimeters
ATLAS electromagnetic Calorimeteraccordion geometry absorbers immersed in Liquid Argon
(RD3 / ATLAS)
Liquid Argon (90K)+ lead-steal absorbers (1-2 mm)+ multilayer copper-polyimide
readout boardsionization chamber.
1 GeV E-deposit 5 x106 e-
• geometry minimizes dead zones.• liquid Ar intrinsically radiation hard.• readout board allows fine
segmentation (azimuth, pseudo-rapidity & longitudinal) accordingto the physics needs
Test beam results, e- 300 GeV (ATLAS TDR)
cEbEaEE /)(spatial &angular
uniformity0.5%
spatialresolution5 mm / E1/2
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/36
CMS hadron calorimeterCu absorber + scintillators
Sampling calorimeters
scintillators fill slots & readout via fibres by HPDs
2 x 18 wedges (barrel) + 2 x 18 wedges (endcap)in total a 1500 ton absorber
%5%65EE
Etest beamresolution forsingle hadrons
Accelerators and Experiments 2008Scintillation & Energy Measurement Kenneth Österberg VII/37
Jet clustering