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

7. Microstrip Gas Chamber Multiwire Proportional Chamber GEM Micromegas μ cat, μ Groove, μ Dot Typical cell size>1 mm Typical cell size ~ 100 μ m Due to small dimensions, Streamers develop easily into sparks!

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

9. ALICE/HMPID concept of CsI RICH - liquid C 6 F 14 radiator - proximity focussing geometry - small gap MWPC (~2 mm) - cathode pads coated with CsI 1 st generation gas based photodetector with CsI photocathodes (PCs) 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 NA44 / TIC @ CERN (0.3 m 2 ) finished STAR / RICH @ BNL (1 m 2 ) finished HALL-A / RICH @ JLab (0.7 m 2 ) running HADES / RICH @ GSI (1.5 m 2 ) running ALICE / HMPID @ CERN (11m 2 ) next year COMPASS / RICH1 @ CERN (5.8 m 2 ) running Experiments with CsI RICH (active area m 2 ) MWPC front-end electronics pad cathode covered with CsI film

10. 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) substrate preparation PC transfer & storage detector assembly, operation & evaluation PC deposition & quality evaluation PHOTOCATHODES: processing under vacuum and detector assembly & operation under gas Need state of the art technologies: - vacuum technology - multi-source thin film coating - quality evaluation - in situ encapsulation - cleanroom facilities Technology of photocathodes Recent papers: BK Singh et al., NIM A454 (2000) 364 E.Shefer, J. App. Phys 92 (2002) 4758

13. Sealed visible gaseous photomultiplier

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

15. Simulation of the avalanche process in a single THGEM Ar/CO 2 (70:30) 760 Torr  V THGEM =600 V e coll = e - collected in the holes e - produced above the holes F extrac = e - extracted from the holes e - produced in the holes

16. GEM Hardware Plan Efficient operation of GEM/THGEM needs:  V GEM - (focussing, Gain, backscattering etc) E extr E trans Geometry (GEM/THGEM) Gas/Gas purity - low backscattering and sufficient Gain

17. 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 ( 55 Fe) 10 mCi