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Development of RICH

Development of RICH. Serguei Sadovsky IHEP, Protvino CBM meeting GSI, 8 October 2004. Outline. Conceptual design of RICH Optics Be-glass mirrors Radiator gases Small diameter PMT FEU-Hive Inputs for RICH FEE Simulation results Conclusion. Conceptual design of RICH1.

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Development of RICH

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  1. Development of RICH Serguei Sadovsky IHEP, Protvino CBM meeting GSI, 8 October 2004

  2. Outline • Conceptual design of RICH • Optics • Be-glass mirrors • Radiator gases • Small diameter PMT FEU-Hive • Inputs for RICH FEE • Simulation results • Conclusion

  3. Conceptual design of RICH1 • 2.2-m long gas radiator with 40%He+60%CH4, pure N2 or 60%N2+40%CH4 gas mixture • Two identical walls of the hexagonal spherical Be-glass mirros • Two photo-detector planes with aperture 3x0.6 m2 each on the base of PMT FEU-Hive • Support structure for photo-detector planes and mirror walls • Gas vessel with beam pipe in the center and gas supply system

  4. Optical scheme of the RICH1 detector V.Khmelnikov Vertical Horizontal

  5. RICH in CBMroot

  6. Be-glass mirrors, production details • Curvature radius of the mirror surface is 450 cm • The maximal size of the Be hexagons is 60 cm • Mirror thickness is 3 mm of Be and 0.5 mm of glass, i.e. in total 1.25% of X0 • The weight of one hexagon is 1.3 kg heater High temperature (~600C) glass beryllium

  7. Be-mirror prototype without Al covering, photo

  8. Be-mirror prototype, optics quality measurements • Angle deviation from the nominal value σθ=0.03 mrad • Image diameter of a point sours (95% of the sours intensity) D0=0.4 mm • The optical surface roughness σh of mirror is 1.6 nm after the glass polishing, Al covering and SiO2 coating

  9. Be-mirror reflectivity in dependence on photon wave length • The optical surface roughness σ of mirror is 1.6 nm • Total reflectivity R0 of mirrors with Al coverage is 92% • Specular reflectivity Rsp = R0exp(-4תσ/λ) and defuse reflectivity Rdf =R0-Rsp A.Braen & M.Kostrikov, Preprint IHEP 93-129

  10. Upper wall of the hexagonal Be-glass mirrors in terms of hexagons, aperture is 4.5x1.75m2

  11. one quarter of mirror/ photodetector: f = 80o 60o 40o q = 5o 10o 15o 20o 25o 30o 35o 20o Be-mirror wall, optics simulation Claudia Höhne • rings(q,f) - q polar angle, • f azimuth angle • no diffusion at reflection • no magnetic field, no multiple scattering Simulation result: Optics distortions (eccentricity) for large q,f To do: improve optics of the mirror walls / focussing position of focal planes

  12. Radiator gases, properties N2 60% N2+40%CH4 40%He+60%CH4 n 1.000298 1.000356 1.0002804 gth 41 37.5 42.24 pp,th 5.72 GeV/c 5.25 GeV/c 5.9 GeV/c Qc 1.398o 1.53o 1.36o X0 304 m 386 m 999 m Dispersion of refractive index: N2 A=29.0610-5 B=7.7 10-3 He A=3.48 10-5 B=2.3 10-3 CH4 A=42.6 10-5 B=12.0 10-3 *

  13. Radiator gases, transmittances [Y.Tomkiewicz and E.L.Garwin, NIM V114 (1974) pp. 413-416] [L.Fabbietti for HADES, NIM A 502 (2003) 256]

  14. Photo-detector plane • Hexagonal packing of the small diameter PMT FEU-Hive with glass cathode window • WLS films for detection of 100 - 330 nm ultraviolet photons • Improvement of the photon collection by special Al foil inserts

  15. Aperture optimization of the Photo-detector plane Yuri Kharlov UrQMD PLUTO

  16. The PMT FEU-Hive as the UV detector • The PMT FEU-Hive has been designedin cooperation of IHEP with the Moscow Electrolamp Company (MELZ) on a base of the resistive distributed dynode system with electrostatic focusing, bialkaline photo-cathode and tube with a glass window. • The electrostatic optics, construction details and PMT parameters have been optimized by using computer model of the PMT. • By means of the optics and dinode system optization one achieves effective operation of the PMT in one-photo-electron regime, which isimportantfor applicationin RICH detectors.

  17. Parameters of the PMT FEU-Hive V.Rykalin, R.Sidoreev rykalin@mx.ihep.su • External PMT diameter is 6 mm • Photo-cathode diameter is 5 mm • PMT length is 60 mm • Photo-cathode: K2CsSb • Quantum efficiency at 410 nm is 25% • Effective number of dynodes is 12 • Nominal HV is less than 2 kV • Amplification is 106 • Dynamical charge range is 0.25-2.5 pC • Noise current is 3000 e/sec • Capacitance is 15 pF • Power dissipations is 40 mW • Price is less than 25 Euro/PMT

  18. PMT FEU-Hive, quantum efficiency FEU-Hive, Radiant sensitivity

  19. PMT FEU-Hive, simulation results Photons/PMT in UrQMD One photoelectron spectrum Pulse jitter

  20. V.Leontiev, M.Bogolyubsky Inputs for RICH Front End Electronics on the base of the PMT FEU-Hive: • Negative polarity of the output signals • Total charge in a pulse – from 0.25 to 25 pC • Noise -- 3000 e/sec • Pulse lenght -- several ns • Output capasitance -- 15 pF • ADC bit number -- 8-9 bits • Channel density -- 2.5 channels /cm2 • Total number of channels – 60000-120000 • There is a limitation on the total power consumption of RICH electronics placed in gas vessel

  21. V.Leontiev, M.Bogolyubsky HV regulation • Classical scheme of the HV regulation with ballast resistor and PMT dividing sercuit • The ballast resistor has 6 bit regulation in the region 1.6-2 kV, i.e. with 6V step • Do we really need such fine HV regulation? • This is question to the production technology ... • and avaliable space, we have only 0.4 cm2/channel

  22. Dmitri Seliverstov, RIE Another option of UV photo-detector • Multianode fine-mesh PMT on the base FEU-187, RIE St.Petersburg: - diameter 25.4-30 mm - lenght 65 mm - gain 10^6 - quantom efficiency lies in 300-600 nm, at 425 nm it is 25% - time resolution with plastic scintillators-40-50 nsec (sigma). - 15 stage dinode system performs in axial magnetic field 2 Tesla - 3x3 picels with pixel size 5x5 mm2 and diameter of 25.4 mm - 4x4 pixels with pixel size 5x5 mm2 and diameter of 30 mm - the PMT can be produced with square tubes, size 25x25 mm2 - the main problem is to obtain a good oneelectron sensitivity

  23. Claudia Höhne Yuri Kharlov Boris Polishchuk RICH simulation CbmDetector CbmTask CbmRich CbmRichHitProducer CbmRichRingGuidanceProducer CbmRichRingFinder CbmRichPoint CbmRichHit CbmRichMirrorPoint CbmRichRingGuidances CbmRichRing CbmMCPoint CbmHit TObject

  24. Single particle response: N(p) 50%N2+50%CH4 40%He+60%CH4 N2

  25. Single particle response: R(p) 50%N2+50%CH4 40%He+60%CH4 N2

  26. Ring multiplicity in Au-Au collisions 40%He+60%CH4: 37 rings 50%N2+50%CH4: 39 rings N2: 41 rings

  27. Detector occupancy • On average 700-900 fired PMT per event • Not taken into account yet: • noise yet • diffusive reflection • possible gas fluorescence

  28. MC points + hit s + rings y [cm] photodetector plane: 1 central Au+Au collision, 25 AGeV (UrQMD) hits + rings (primary vertex tracks) + ring center guidances (= extrapolation of charged tracks from primary vertex) x [cm]

  29. Summary • Conceptual design of RICH1 is ready • Realistic CBMroot model of RICH1 has been written, some polishing is still needed • There are 3 options of gas radiator: N2, 60%N2+40%CH4, 40%He+60%CH4, we have to choose the optimal • The gas radiator option is essential for design of the gas vessel and gas supply system • Be-glass mirrors are chosen as the main option, prototype exists, no any problems here • Small diameter PMT FEU-Hive are proposed as main option for the UV photo-detector • Computer model of the PMT FEU-hive exists, construction optimization has been performed, prototyping is needed • Conceptual design of the RICH1 mechanics is need • The first version of the ring reconstruction is written • We need detail simulation of the RICH1 for the project tuning.

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