simulation of a ring imaging cerenkov detector to identify relativistic heavy ions....
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Simulation of a Ring Imaging Cerenkov detector to identify
relativistic heavy ions.
M.Fernández-Ordóñez, J.Benlliure, E.Casarejos, J.Pereira
Universidad de Santiago Compostela
ToF techniques present severe constraints to achieve a velocity resolution 10-3 for large angular ranges.
RICH advantages:High velocity resolution.Large angular aceptance.
RICH disadvantages:Beam intensity loss due to nuclear interactions.Loss in identification resolution due to atomic interactions.
RICH
Motivation:Detailed simulations of the Cerenkov detector to determinethe optimum radiator thickness and radiator nature.
Cerenkov radiation characteristics
Nature Material n Tth
Gas He 1.000035 > 110 GeV/u
Aerogel 1.004 > 9 GeV/u
Aerogel 1.1 1.3 GeV/u
Liquid C6F14 1.28 550 MeV/u
Solid MgF2 1.43 375 MeV/u
Solid SiO2 1.56 280 - 750 MeV/u
2
2 11
nLZ
cdE
dN ph
Frank-Tamm relation:
nC
1cos
nTth
1
Simulation walength range: U-V.
Simulations with the code GEANT 3.21
-Setup geometry.-Particle tracking.-Interactions of heavy-ions with matter:
-Energy loss.-Energy straggling.-Angular straggling.
-Cerenkov radiation:-Dispersion law.-Transmission.-Abortion proccesses.
-Photon Detector:-Quantum efficiency-Granularity.
Velocity determination from the Cerenkov ring radii
1)(
11
21
22
22122
1
nn
nLndR
R
R
N ph
1
E
C
2
2
tan1
tan
8 mm thickness C6F14 radiator.96Ru at 1 GeV/u
Numerical solutionPhoton emission at the middle of the radiator.Mean refractive index.Algorithm accuracy.
R = r.m.s of the data setNph= number of detected photons
Simulated performances of different radiators
96Ru600 MeV/u700 MeV/u for C6F14
2 mm thickness4 mm for C6F14
-The radiators have different ranges.-The required velocity resolution is achieved for ions above Z=15.-The effect of the dispersion law is observed.-The effect of the energy loss in the radiator is also observed.
(2mm)
C6F14 (4 mm)
(2mm)
Simulated performances of different radiators
-The energy loss compensates the photon statistic (radiator thickness).-The dispersion law compenstes the granularity of the photon detector.
96Ru
600 MeV/u
800 MeV/u
96Ru
700 MeV/u
600 MeV/u
2 mm
4 mm
Key experiments: Fission 238U + Pb (600 A MeV)
-Multiple ring events.-Large angular range.-Thick target.
Radius distribution
Atomic interactions for 96Ru
Key Experiments: Fission 238U + Pb (600 A MeV)
Kinetic energy resolution
T=f(v,)
T=f (E, )
Energy range of the fissioning system: -450-600 MeV/u for SiO2.
-Above 550 MeV/u for MgF2
v and are given by Wilkins
Proposed radiator: SiO2 (2 mm)
Key experiments: Spallation 208Pb + p (600 A MeV)
)·3(2
1 22cmcmvmT
From Morrisey
Primary interactionsKinetic energy resolution
Reaction probabilities
Key experiments: Spallation 56Fe + p (600 A MeV)
Reaction probabilities
Primary interactions
Kinetic energy resolution
Key experiments: Fragmentation 132Sn + Pb (600 A MeV)
Primary interactions
Kinetic energy resolution
Reaction probabilities
Key experiments: Spallation 208Pb + p (1000 - 500 A MeV)
-Thin Target.-Large energies: total internal reflexion.
Atomic interactions for 175Re:
Key experiments: Spallation 208Pb + p (1000 - 500 A MeV)
Velocity resolution for SiO2
In total reflexion mode (2 mm).
Proposed radiator: MgF2 (2 mm) or SiO2 (2 mm) in total reflexion.
)·3(2
1 22cmcmvmT
Kinetic energy resolution from:
Conclusions-RICH detectors are better suited than ToF techniques to achieve high accuracyvelocity measurements for large angular ranges. However they induce additionaluncertainty sources: atomic and nuclear interactions Simulation.
-Detailed simulations of the detector: geometry, particle tracking, interactionsof heavy-ions with matter, Cerenkov radiation, transmissions, photon absortion,quantum efficiency and granularity of the photon detector.
-Comprehensive analysis of the performances of different radiators: radiator thicknessand radiator nature.
-Simulation of key experiments:Fission experiments: multiple rings, large angular range, thick targets.
Proposed radiator SiO2 (2 mm)Spallation experiments: large energy range, thin targets.
Proposed radiator MgF2 (2 mm) or SiO2 (2 mm) total reflexion.