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Focusing Aerogel RICH Optimization

Focusing Aerogel RICH Optimization. A . Yu . Barnyakov , M . Yu . Barnyakov , V . S . Bobrovnikov , A . R . Buzykaev , V . V . Gulevich , S . A . Kononov , E . A . Kravchenko, A . P . Onuchin Budker Institute of Nuclear Physics, Novosibirsk, Russia A . F . Danilyuk , V . L . Kirillov

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Focusing Aerogel RICH Optimization

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  1. Focusing Aerogel RICH Optimization A.Yu.Barnyakov, M.Yu.Barnyakov, V.S.Bobrovnikov, A.R.Buzykaev, V.V.Gulevich, S.A.Kononov, E.A.Kravchenko, A.P.Onuchin Budker Institute of Nuclear Physics, Novosibirsk, Russia A.F.Danilyuk, V.L.Kirillov Boreskov Institute of Catalysis, Novosibirsk, Russia Presented by E.A.Kravchenko

  2. Outline • RICH with aerogel and NaF radiators • Multilayer aerogel for FARICH • Xray measurement of longitudinal refractive index variations • MC simulation of real experimental 3-layer aerogel block • Status of aerogel production in Novosibirsk • Conclusion E.A.Kravchenko, "Focusing aerogel RICH optimization"

  3. √2 Sodium fluoride radiator Suggested for RICH with a TEA/TMAE pad-photon detector by R. Arnold et al. [ NIM A273 (1988) 466 ] • CAPRICE RICH (balloon-borne, flight in 1994): • 10mm thick NaF looked by MWPC with TMAE, pad read-out. • AMS-02 RICH (ISS-borne, tested with beam 2003): • 34x34x0.5cm NaF & aerogel n=1.05 looked by MA-PMT array • Good transparency in visible & near UV, • Almost no light scattering as compared with aerogel, • More firm and stable material, though toxic. NaF has the lowest refractive index among solids (except aerogel). for λ >170 nm Cherenkov photons refracts out for normal incidence particle, β≈1 E.A.Kravchenko, "Focusing aerogel RICH optimization"

  4. Aerogel radiators for comparison • SLA 12mm – single layer aerogel with n=1.07 • SLA 24mm – single layer aerogel with n=1.07 • FASR-6 – 6-layer aerogel with single ring • FAMR-3 – 3-layer aerogel with 3 rings FASR-6 gives the best performance at β≈1: Npe = 13, σβ= 5∙10-4 π/K separation up to 8 GeV/c (better 3σ) A.Yu. Barnykov, et al., NIM A553 (2005) 125 A.Yu.Barnyakov, et al., Proceedings of SNIC 2006,eConf C0604032 (2006) 0045 • A low momentum solution wanted below aerogel threshold: • Time-of-flight built in aerogel RICH( suggested and tested by Belle RICH group) • Higher refractive index radiator E.A.Kravchenko, "Focusing aerogel RICH optimization"

  5. Monte Carlo simulation (GEANT4) Physics • The processes defined: • for charged particles: Cherenkov emission, multiple scattering • for optical photons: Fresnel refraction and reflection, Rayleigh scattering, bulk absorption. • Effects considered: • Dispersion of refractive index • Emission point uncertainty • Scattered photons are discarded • Position resolution of photodetector not considered Detector components • Geometry:D = 100 mm (200 mm) - from radiator input face to photodetector plane • Aerogel properties: • Rayleigh scattering length: 5 cm at 400 nm • Aerogel bulk absorption length: 400cm at 400 nm • Photodetector: • Bialkali photocathode with borosilicate window QEmax=24% • Overall efficiency factor: 50%(packing density & pe collection efficiency) E.A.Kravchenko, "Focusing aerogel RICH optimization"

  6. kaons @ 3.5 GeV/c σθ Npe Optimization of NaF radiator Thickness 10 mm=> 9% X0at normal incidence E.A.Kravchenko, "Focusing aerogel RICH optimization"

  7. Normal incidence particles 30o incidence NaF vs aerogel E.A.Kravchenko, "Focusing aerogel RICH optimization"

  8. π/K separation normal incidence 30o incidence NaF: up to 5 GeV/c NaF: up to 3.5 GeV/c Radiator in the endcap can be tilted so that: |θi|<20o E.A.Kravchenko, "Focusing aerogel RICH optimization"

  9. Single photon position resolution NaF is less demanding to pixelization. ~ 4∙103 channels in the forward RICH of SuperB detector (100 mm expansion gap) • Single layer aerogel RICH with 100 mm expansion gapneeds 105 channels, focusing RICH – 4∙105 channels) E.A.Kravchenko, "Focusing aerogel RICH optimization"

  10. NaF-aerogel multi-ring radiator concept FASR NaF The focusing condition for aerogel is yet to be investigated… E.A.Kravchenko, "Focusing aerogel RICH optimization"

  11. Multilayer aerogel 100x100x41 mm, Lsc = 45 mm at 400 nm E.A.Kravchenko, "Focusing aerogel RICH optimization"

  12. Xray measurement, density distribution The increase in density at the internal borders is the result of the production procedure (diffusion). Does it effect the performance? E.A.Kravchenko, "Focusing aerogel RICH optimization"

  13. Monte Carlo simulation of longitudinal refractive index fluctuations • 200 mm expansion gap • 3 types of radiators • 3layer as designed (ideal) • Xray data avereged to 3 layers • Xray data avereged to 14 layers E.A.Kravchenko, "Focusing aerogel RICH optimization"

  14. Simulation results, π/K separation • Npe =14 • σβ = 5∙10-4 • ‘optimal’ radiator → best resolution for 4 GeV/c pions • ‘real’ experimental radiator → best resolution for 3.5 GeV/c kaons • π/K separation up to 8 GeV/c (>3σ) E.A.Kravchenko, "Focusing aerogel RICH optimization"

  15. Status of aerogel production • ~2000 liters have been produced for KEDR ASHIPH detector, n=1.05 • 14 blocks 20020050 mm have been produced for LHCb RICH, n=1.03 • ~200 blocks 11511525 mm have been produced for AMS RICH, n=1.05 • n=1.13 aerogel for SND ASHIPH detector • n=1.008 aerogel for the DIRAC • 3-4 layers focusing aerogel High optical parameters (Lsc≥43mm at 400 nm) Precise dimensions (<0.2 mm) See poster of A. Danilyuk “Progress in aerogel synthesis in Novosibirsk” E.A.Kravchenko, "Focusing aerogel RICH optimization"

  16. Conclusion • Use of NaF radiator in the forward RICH looks very promising (PID at low momenta, small number of channels) • Large 3 layers aerogel block has been produced and characterized • The Monte Carlo simulation taking into account the real longitudinal refractive index fluctuations shows small distinction of resolution between ‘real’ and ‘ideal’ aerogel radiators. E.A.Kravchenko, "Focusing aerogel RICH optimization"

  17. Additional slides E.A.Kravchenko, "Focusing aerogel RICH optimization"

  18. Technical requirements on multilayer aerogel, single ring (layer thickness) • Accuracy on the thickness of the layers • 2 cases – • “correlated” (all layers change equally) • “anti-correlated” (half of the layers increase, other decrease) E.A.Kravchenko, "Focusing aerogel RICH optimization"

  19. Technical requirements on multilayer aerogel, single ring (index of refraction) • Accuracy on the refractive index • in the layers • 6-layer option • 2 cases – • “correlated” (all layers change equally) • “anti-correlated” (half of the layers increase, other decrease) E.A.Kravchenko, "Focusing aerogel RICH optimization"

  20. Technical requirements on multilayer aerogel, single ring (longitudinal density variations) • Accuracy on the density variations along the track • case sensitive • negative – variation in the layer from low values to high (continuous focusing) • positive – variation from high values to low Technical requirements on multi ring aerogel are more simple! E.A.Kravchenko, "Focusing aerogel RICH optimization"

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