detectors of charged particles and ions 1) gas filled detectors a) ionization chambers b)...
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Detectors of charged particles and ions
1) Gas filled detectors
a) Ionization chambers b) Proportional counters c) Multiwire chambers d) Time projection chambers
2) Scintillation detectors
3) Semiconductor detectors
Mostly high efficiency (ionization will start immediately),big enough detector – absorption of whole energy
Silicon detectors of alpha particles produced by CAMBERA company
Hadron calorimeter of NA49 experiment Calorimeter of ATLAS experiment
Scintillation detectors
dx
dEkB
dx
dEA
dx
dL
1
A – absolute scintillation efficiency, kB – parameter which joins density of ionization centers with ionization
Semiempirical Birks equation:
Response on heavy charged particles:
Non-linearity for L = f(E) starts to manifest
Response of fast plastic scintillator on heavy ions
Limited number of scintillation centers → saturation –part of energy is not converted
(mainly for organic scintillator)
dx
dE
dx
dL
dx
dE~0
dx
dE
dx
dLkB ~0
0~ kB
A
dx
dLkB
saturation: )(ERkB
AL
Many other variants of semiempirical equations
kB
A
dx
dL
dx
dE~
Dependency of light output on ionization losses
Dependency of light output on kB
dx
dEf
dx
dL
)(kBfdx
dL
dxdx
dLL
Total light output L:
Differentiation of different ions by means of analysis of puls shape:
Short and long components of de-excitation – de-excitation of different excited states(ratio of their excitation probability depends on ionization losses)
Possibility to use two types of scintillator with different de-excitation time
Differentiation by means of comparison of light outputs with different time window: BaF2 spectrometer TAPS (right) and CsI(Tl) (left)
L(short)
L(l
ong)
Dependency of response on energy for plastic scintillator NE102A
ΔE-E telescopes 2 mm plastic and CsI scintillator
E
ZE
2
Compensation calorimeter:
Hadron calorimeters
Transversal energy flow and longitudinal energy flow – escape from detector
Bigger response to particles of elmg component Le/Lh = 1,1 – 1.35
Suitable active and passive calorimeter parts: Le/Lh ≈ 1
Possibility of correction during later analysis – usage of information about course of shower
238U – absorption of slow neutrons, shielding from soft photons by layers of materials with small Z
Absorption of photons from neutron captures by means of atoms with large Z
End of hadron shower E ~ ETHR(π) ~ 100 MeV – threshold of π mesons production
Detection of large amount of created neutrons (5 neutrons/GeV), their energies ~ 8 MeV
Uncertainty consists of three components: 1) statistical fluctuations:
2) detector – noise, pedestals:
3) calibration – photomultiplier nonlinearity, in homogeneities:
EEf 1
EED 1
konstEK
Forward calorimeter of ALICE experiment