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

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

3. B M C Conceptual design of RICH1 2.2-m long gas radiator with 40%He+60%CH 4, pure N 2 or 60%N 2 +40%CH 4 gas mixture Two identical walls of the hexagonal spherical Be-glass mirros Two photo-detector planes with aperture 3x0.6 m 2 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. B M C Optical scheme of the RICH1 detector Vertical Horizontal V.Khmelnikov

5. B M C RICH in CBMroot

6. B M C 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 X 0 The weight of one hexagon is 1.3 kg beryllium glass heater High temperature (~600  C)

7. B M C Be-mirror prototype without Al covering, photo

8. B M C Be-mirror prototype, optics quality measurements Angle deviation from the nominal value σ θ =0.03 mrad Image diameter of a point sours (95% of the sours intensity) D 0 =0.4 mm The optical surface roughness σ h of mirror is 1.6 nm after the glass polishing, Al covering and SiO 2 coating

9. B M C Be-mirror reflectivity in dependence on photon wave length The optical surface roughness σ of mirror is 1.6 nm Total reflectivity R 0 of mirrors with Al coverage is 92% Specular reflectivity R sp = R 0 exp(-4תσ/λ) and defuse reflectivity R df =R 0 -R sp A.Braen & M.Kostrikov, Preprint IHEP 93-129

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

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

12. B M C N 2 60% N 2 +40%CH 4 40%He+60%CH 4 n 1.000298 1.000356 1.0002804  th 41 37.542.24 p ,th 5.72 GeV/c5.25 GeV/c 5.9 GeV/c  c 1.398 o 1.53 o 1.36 o X 0 304 m386 m999 m Radiator gases, properties N 2 A=29.06 10 -5 B=7.7 10 -3 HeA=3.48 10 -5 B=2.3 10 -3 CH 4 A=42.6 10 -5 B=12.0 10 -3 * Dispersion of refractive index:

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

14. B M C 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. B M C

16. B M C Yuri Kharlov Aperture optimization of the Photo-detector plane UrQMD PLUTO

17. B M C The PMT FEU-Hive as the UV detector The PMT FEU-Hive has been designed in 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 is important for application in RICH detectors.

18. B M C Parameters of the PMT FEU-Hive External PMT diameter is 6 mm Photo-cathode diameter is 5 mm PMT length is 60 mm Photo-cathode: K 2 CsSb Quantum efficiency at 410 nm is 25% Effective number of dynodes is 12 Nominal HV is less than 2 kV Amplification is 10 6 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 V.Rykalin, R.Sidoreev rykalin@mx.ihep.su

19. B M C PMT FEU-Hive, quantum efficiency FEU-Hive, Radiant sensitivity

20. B M C PMT FEU-Hive, simulation results One photoelectron spectrum Pulse jitter Photons/PMT in UrQMD

21. B M C 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 V.Leontiev, M.Bogolyubsky

22. B M C 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 V.Leontiev, M.Bogolyubsky

23. B M C 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 Dmitri Seliverstov, RIE

24. B M C RICH simulation Claudia Höhne Yuri Kharlov Boris Polishchuk CbmDetector CbmMCPointCbmHit CbmTask CbmRich CbmRichPoint CbmRichHit CbmRichHitProducer CbmRichMirrorPoint CbmRichRingGuidanceProducer CbmRichRing CbmRichRingFinder CbmRichRingGuidances TObject

25. B M C Single particle response: N(p) 40%He+60%CH 4 N2N2 50%N 2 +50%CH 4

26. B M C Single particle response: R(p) 40%He+60%CH 4 N2N2 50%N 2 +50%CH 4

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

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

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

30. B M C 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.