The CRES RICH

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The CRES RICH. CE renkov R ing E lectron S pectrometer at the CERN SPS (1990-2000) www.physi.uni-heidelberg.de/physi/ceres Presented by Peter Gl ässel, Heidelberg (now ALICE ). Univ. Heidelberg, H.J. Specht Weizmann Institute, Rehovot, I. Tserruya MPI-K Heidelberg, J.P. Wurm - PowerPoint PPT Presentation

Text of The CRES RICH

  • The CRES RICH

    CErenkov Ring Electron Spectrometer at the CERN SPS (1990-2000) www.physi.uni-heidelberg.de/physi/ceres

    Presented by Peter Glssel, Heidelberg (now ALICE)Univ. Heidelberg, H.J. SpechtWeizmann Institute, Rehovot, I. TserruyaMPI-K Heidelberg, J.P. WurmPolitechnico di Milano, E. GattiBNL, P. RehakCERN, J. Schukraft

    CBM - RICH - Workshop 6.3.06

  • OutlineCERES setupRadiators and windowsMirrorsUV-photon detectorsUnderstanding performanceSummary

    CBM - RICH - Workshop 6.3.06

  • CERES RICH layoutaxially symmetric

    CBM - RICH - Workshop 6.3.06

  • CERES in 1996

    CBM - RICH - Workshop 6.3.06

  • Radiator and UV windowsCH4 at ambient pressure = 32O2 and H2O about 1 ppmRICH1, L = 90 cm window CaF2 in Al alloy UV bandwidth limited by radiator gas CH4RICH2, L = 175 cm window quartz (Haereus Suprasil) in Invar frame, sliding O-ring seal vs. radiator tankbandwidth limited by quartz

    CBM - RICH - Workshop 6.3.06

  • UV1 CaF2 window10 mm thick10 sectors, each consisting of 4 pieces, gluedAl alloy (cast) with tuned thermal expansion coeffborder to CaF2 shaped like a bellow (1mm wall)

    CBM - RICH - Workshop 6.3.06

  • CERES RICH mirrorsRICH1: 1 mm CFK, replica-molded on glas master~60 cm Invar ring mountReflectivity typ > 85%, 70% @ 140 nmOptical quality does not limit RICH resolutionRICH2: ring-shaped, 10 sectors ~ 1.8 m 6 mm glas, slumping method from flat glass (Andre Braem/ CERN)After software-correction for focal length variations: does not limit RICH resolution

    CBM - RICH - Workshop 6.3.06

  • RICH1 Mirror1 mm CFK replica on glas master~ 60 cm Invar ring mountReflectivity: avg. 85%, 70% @ 140 nmOptical quality does not limit RICH resolution

    CBM - RICH - Workshop 6.3.06

  • RICH2 Mirrorring-shaped 10 sectors ~ 1.8 m 6 mm glas, slumping method from flat glass (Andre Braem/ CERN)After offline-correction for focal length variations: does not limit RICH resolution

    CBM - RICH - Workshop 6.3.06

  • The CERES UV detectors, 1st try

    CBM - RICH - Workshop 6.3.06

  • Assembly of UV2

    CBM - RICH - Workshop 6.3.06

  • UV2 detector

    CBM - RICH - Workshop 6.3.06

  • Why did 2-step (or 3-step) PPAC not work?Avalanches 5107 108 e spark (Raether Criterion 1939)Independent of quencher Fonte, Pestov, Sauli NIM A305(1991)91Gas gain x dE/dx in typ. avalanche dimension: 105 x 1000 e/mm x 1 mm = 108Slow knock-on protons from shower neutrons do it!CERES: in 32S+Au: 20% spark probability per interaction in UV2 (3 m2)

    Solution: fundamentally different behavior of the multiplication schemes in the space-charge limit:PPAC: gain divergesMWPC: gain saturates

    New scheme worked up to Pb-Au ( 20 % dead time due to sparks)Last stage must be a MWPC

    CBM - RICH - Workshop 6.3.06

  • The CERES UV detectors from 1992 on

    CBM - RICH - Workshop 6.3.06

  • UV1 multi-wire anode plane

    CBM - RICH - Workshop 6.3.06

  • Other UV detector specsMeshes stainless steel, 50 m , 500x500 m pitch, except first mesh (30 m for higher transparency)Materials: G10 frames, stainless steel, teflon, delrin, Cu, selected epoxyResistive layer: carbon-filled epoxy, 150 M/MWPC: anodes 30 m , 2 (3) mm pitch53.800 (48.400) padsHe + 6% CH4 + TMAE(400 C) at ambient pressure, operated at 500 CGas gain 2 4105Detectors functioned for 7 beam periods

    CBM - RICH - Workshop 6.3.06

  • Event displaysClose-up of e+e pair

    CBM - RICH - Workshop 6.3.06

  • Event displayPb-Au

    CBM - RICH - Workshop 6.3.06

  • Understanding N0from: CERES Status Report to the SPSLC, CERN SPSLC/94-02

    CBM - RICH - Workshop 6.3.06

  • Understanding Resolution

    CBM - RICH - Workshop 6.3.06

  • Cherenkov Ring Radial distributionRing center resolution: 1-dim, for tracking, momentumc = 1.6 h / sqrt(N)

    CBM - RICH - Workshop 6.3.06

  • Single hit background

    CBM - RICH - Workshop 6.3.06

  • SummaryTMAE is a manageable UV-converterBeware of spark limit for any gas multiplication schemeTheoretical performance limits can be closely reached in practice

    CBM - RICH - Workshop 6.3.06

    Still missing: FEE timelineMore ALTRO testsFEC photoIntegration issuesPASA result table