RICH Development Serguei Sadovsky IHEP, Protvino CBM meeting GSI, 9 March 2005

B M C Outline Conceptual design of RICH RICH mechanics Photo-detector plane Simulation results R & D planes Conclusion

B M C Conceptual design of RICH 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 small diamter PMT or gaseous detector Gas vessel with beam pipe in the center Mirror walls, photo-detector planes and support structures are inside of the gas vessel Be- glass mirrors, production details

B M C RICH mechanics overview Flanch Flanch ? Flanch RICH Mechanics meeting, St.Peterburg, Gas vessel Magnet Horizontal view

B M C RICH mechanics overview (cont.) RICH Mechanics meeting, St.Peterburg, Gas vessel at atmospheric pressure Mirror walls are inside of the gas vessel Mirror supports are similar to those in LHCb Mirror optics tuning is inside of the gas vessel Photo-detector planes are inside of the gas vessel Photo-detector planes have probably to be cooled The key elements of the RICH mechanics are the vacuum tube and the relevant flanches

B M C RICH mechanics, open questions: RICH Mechanics meeting, St.Peterburg, Is the vacuum tube a part of RICH ? Is RICH detachable detector? I.e. can RICH be removed from the beam and after be returned back? or it will be assembled one time in its own place around the vacuum tube for all time of the experiment. Will be optics tuned by man or by the special fine mechanics & electronics

B M C Photo-detector plane, ½, as consisting from photo-detector units

B M C Photo-detector unit, 397 PMTs N PMT =(3n-2)(n-1)+2n-1 n=12 D = 7x(2n-1) mm d = 7xn mm 84 mm 161 mm PMT FEU-Hive Cherenkov ring, R=55mm

B M C Photo-detector cell on the base of the PMT FEU-Hive PMT diameter, D = 6 mm Photo-cathode, d = 5 mm High requirements to the one-photoelectron regime

B M C Photo-detector, PMT FEU-Hive, the mechanical prototype, 7 March 2005

B M C Photo-detector, Si HPM FEU-Pike, the mechanical prototype, 7 March 2005

B M C Electron rings after the photo-detector plane tilding Focussing is perfect But sperical abberation is still clearly seen Claudia Höhne RICH simulation, mirror optics

B M C RICH simulations: ring radius resolution vs lower limit of the UV photon region Boris Polishchuk We have no reason to go in the UV region below 150 nm

B M C RICH simulations: ring radius resolution vs PMT radius Boris Polishchuk Taking into account effect of chromatic distortion the PMT diameter of 6-7 mm is close to the optimal

B M C RICH ring recognition algorithm was elaborated. It starts from the coarse histogramming of source data. Then all areas corresponding to separate or overlapped rings are found by clustering. A fragment of this histogram is shown here. One can see that clustering splits this frgment into three areas corresponding to one or two overlapped rings RICH simulation, RICH ring finder Gennadi Ososkov, Boris Polishchuk

B M C Ring centers and radii are found by 2D Hough transfom (HT). It is done by calculating centers {xc, yc} and radii of circles drawn through every possible triplet of points from the selected group. Each time distances between points and obtained radii of a triplet are tested to be within prescribed limits. A fragment of HT histogram for ring centers. Two maxima are seen corresponding to two rig centers. RICH simulation, RICH ring finder (2) Gennadi Ososkov, Boris Polishchuk

B M C A result of typical event handling Average time to handle one event is less than 1 sec on 2200 MHz PC. RICH simulation, RICH ring finder (3): Gennadi Ososkov, Boris Polishchuk

B M C [Y.Tomkiewicz and E.L.Garwin, NIM V114 (1974) pp ][L.Fabbietti for HADES, NIM A 502 (2003) 256] Radiator gases, transmittances and refractive index variation N2CH4

B M C R & D plans, what should be measured Radiator gases: - number of the detected Cherenkov photons for PMT with the K 2 CsSb photo-cathode and glass window - number of the Cherenkov photons for the same PMT, but with the WLS film - number of the Cherenkov photons with and without WLS film for different gas radiators (N2, 60%N2+40%CO2, 60%N2+40%CH4, 40%He+60%CH4) - chromatic distortion of ring radiuses in different gas radiators, see above - Fluorecense in N2 and different gas radiators with N2

B M C R & D plans, photo-detectors Photo-detectors on the base of small diameter PMT: - assembly and tests of the full functional FEU-Hive - assembly and tests of the full functional FEU-Pike - test of the FEU-Hive and FEU-Pike in one photoelectron regime Photo-detector on the base of gaseous detectors: - we have to make the full RICH simulation at first because the present RICH simulations were performed for the PMT version only

B M C Conclusion Inputs for the conceptual design of RICH mechanics has to be clarified, including the status of the vacuum tube. The mechanics of LHCb RICH is chosen as prototype for the CBM RICH mechanics The first mechanical prototypes of small diameter PMTs, FEU- Hive and FEU-Pike, have been produced The full functional prototypes of the small diameter PMT have to be produced and tested RICH simulations is now in rather good shape, it allows to perform the realistic tuning of the RICH detector RICH optics have to be improved on the base of RICH simulation We have to perform the full RICH simulation for the gaseous version of the photo-detector plane R & D of different gas radiators has to be performed with the aim of the final choice of gas mixture, that is important for conceptual design of the RICH gas system