1. 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

2. 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 determine the optimum radiator thickness and radiator nature.

3. Cerenkov radiation characteristics NatureMaterialnT th GasHe1.000035> 110 GeV/u Aerogel1.004> 9 GeV/u Aerogel1.11.3 GeV/u LiquidC 6 F 14 1.28550 MeV/u SolidMgF 2 1.43375 MeV/u SolidSiO 2 1.56280 - 750 MeV/u Frank-Tamm relation: Simulation walength range: U-V.

4. 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.

5. Velocity determination from the Cerenkov ring radii 8 mm thickness C 6 F 14 radiator. 96 Ru at 1 GeV/u Numerical solution Photon emission at the middle of the radiator. Mean refractive index. Algorithm accuracy.  R = r.m.s of the data set N ph = number of detected photons

6. Simulated performances of different radiators 96 Ru 600 MeV/u 700 MeV/u for C 6 F 14 2 mm thickness 4 mm for C 6 F 14 -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) C 6 F 14 (4 mm) (2mm)

7. Simulated performances of different radiators -The energy loss compensates the photon statistic (radiator thickness). -The dispersion law compenstes the granularity of the photon detector. 96 Ru 600 MeV/u 800 MeV/u 96 Ru 700 MeV/u 600 MeV/u 2 mm 4 mm

8. Key experiments: Fission 238 U + Pb (600 A MeV) -Multiple ring events. -Large angular range. -Thick target. Radius distribution Atomic interactions for 96 Ru

9. Key Experiments: Fission 238 U + Pb (600 A MeV) Kinetic energy resolution T=f(v,  )  T=f (  E,  ) Energy range of the fissioning system: -450-600 MeV/u for SiO 2. -Above 550 MeV/u for MgF 2 v and  are given by Wilkins Proposed radiator: SiO 2 (2 mm)

10. Key experiments: Spallation 208 Pb + p (600 A MeV) From Morrisey Primary interactions Kinetic energy resolution Reaction probabilities

11. Key experiments: Spallation 56 Fe + p (600 A MeV) Reaction probabilities Primary interactions Kinetic energy resolution

12. Key experiments: Fragmentation 132 Sn + Pb (600 A MeV) Primary interactions Kinetic energy resolution Reaction probabilities

13. Key experiments: Spallation 208 Pb + p (1000 - 500 A MeV) - Thin Target. -Large energies: total internal reflexion. Atomic interactions for 175 Re:

14. Key experiments: Spallation 208 Pb + p (1000 - 500 A MeV) Velocity resolution for SiO 2 In total reflexion mode (2 mm). Proposed radiator: MgF 2 (2 mm) or SiO2 (2 mm) in total reflexion. Kinetic energy resolution from:

15. Conclusions -RICH detectors are better suited than ToF techniques to achieve high accuracy velocity measurements for large angular ranges. However they induce additional uncertainty sources: atomic and nuclear interactions Simulation. -Detailed simulations of the detector: geometry, particle tracking, interactions of 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 thickness and radiator nature. -Simulation of key experiments: Fission experiments: multiple rings, large angular range, thick targets. Proposed radiator SiO 2 (2 mm) Spallation experiments: large energy range, thin targets. Proposed radiator MgF 2 (2 mm) or SiO 2 (2 mm) total reflexion.