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R & D at BHU

R & D at BHU. B.K. Singh (On behalf of HEP Group). Outlines. Introduction Past Experience Present Plan Status. Brief History of Gas Detectors. Gaseous Detectors. Good spatial resolution Fast & big signals Good dE/dx Two tracks resolution Large area coverage

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R & D at BHU

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  1. R & D at BHU B.K. Singh (On behalf of HEP Group)

  2. Outlines • Introduction • Past Experience • Present Plan • Status

  3. Brief History of Gas Detectors

  4. Gaseous Detectors • Good spatial resolution • Fast & big signals • Good dE/dx • Two tracks resolution • Large area coverage • Many possible detector configuration • Low cost

  5. Simulation Tools: • Maxwell (Ansoft) electrical field maps in 2D and 3D, finite elements calculations for arbitrary electrodes and dielectrics • HEED (I. Smirnov) Energy loss, Ionization • MAGBOLTZ (Steve Biagi) (electron transport properties: drift, diffusion, multiplication ) • GARFIELD (R. Veenhof) (Fields, drift properties, signals: interfaced to above program ) These tools allow to simulate accurately detector configurations before constructions.

  6. Past Experience: Gaseous Photomultiplier: MICROPATTERN GAS DETECTORS (GEM) Photocathodes (UV/Visible region)

  7. Multiwire Proportional Chamber Typical cell size>1 mm GEM Microstrip Gas Chamber μcat, μGroove, μDot Micromegas Typical cell size ~ 100μm Due to small dimensions, Streamers develop easily into sparks!

  8. Edrift EHole Etrans Multiplication of electrons induced by radiation in gas or from solid converters (e.g. a photocathode) Semi-transparent photocathode Reflective photocathode Multiplication inside holes reduces secondary effects. (No Photon feedback) THGEMs screen the photocathode

  9. 1st generation gas based photodetector with CsI photocathodes (PCs) ALICE/HMPID concept of CsI RICH - liquid C6 F14 radiator - proximity focussing geometry - small gap MWPC (~2 mm) - cathode pads coated with CsI History Late 1980ies: J.Séguinot & T. Ypsilantis (CERN) Searching for an alternative for TMAE: successful R&D on small samples of reflective CsI PC for UV detection Early 1990ies: F.Piuz et al. CERN / RD26 Study development of large area CsI photo-cathodes for RICH-id. for Heavy Ion Physics MWPC pad cathode covered with CsI film front-end electronics NA44 / TIC @ CERN (0.3 m2) finished STAR / RICH @ BNL (1 m2) finished HALL-A / RICH @ JLab (0.7 m2) running HADES / RICH @ GSI (1.5 m2) running ALICE / HMPID @ CERN (11m2) next year COMPASS / RICH1 @ CERN (5.8 m2) running Experiments with CsI RICH (active area m2)

  10. PHOTOCATHODES:processing under vacuum and detector assembly & operation under gas detector assembly, operation & evaluation substrate preparation PC deposition & quality evaluation PC transfer & storage Need state of the art technologies: - vacuum technology - multi-source thin film coating - quality evaluation - in situ encapsulation - cleanroom facilities Recent papers: BK Singh et al., NIM A454 (2000) 364 E.Shefer, J. App. Phys 92 (2002) 4758 Technology of photocathodes • Requirements for large PCs • good flatness & stiffness •  high & reproducible QE on large area • no contact with humidity (i.e. air) during its full lifetime •  Photodetector must be leaktight • (as should be all utilities)

  11. Sealed visible gaseous photomultiplier

  12. . Sealed Gaseous Detector . Triple GEMs (Kapton made) . Semitransparent K-Cs-Sb photocathode . Stable for few months D. Mormann et al., NIMA 504 (2003) 93. M. Balcerzyk et al., IEEE Trans. Nucl. Sc. NS 50 (2003)847

  13. Simulation of the avalanche process in a single THGEM ecoll = e- collected in the holes e- produced above the holes Fextrac = e- extracted from the holes e- produced in the holes • Ar/CO2 (70:30) 760 Torr • VTHGEM=600 V

  14. GEM Hardware Plan Efficient operation of GEM/THGEM needs: • VGEM - (focussing, Gain, backscattering etc) • Eextr • Etrans • Geometry (GEM/THGEM) • Gas/Gas purity - low backscattering and sufficient Gain

  15. GEM Hardware Plan • NIM Crate • Spectroscopy Amplifier (Ortec 672) • HVPS (CAEN N471 A) • THGEM foil • Gas etc √ Preamplifier (142 AH/IH) √ MCA 8K card with software √ Chamber (plexiglass made) √ Oscilloscope (600 Mhz) √ Laminar flow table • Mesh/ R/O PCB • Source (55Fe) 10 mCi

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