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P HOTON Y IELD DUE TO S CINTILLATION IN CF4 Bob Azmoun, Craig Woody ( BNL ) Nikolai Smirnov ( Yale University )

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Presentation on theme: "P HOTON Y IELD DUE TO S CINTILLATION IN CF4 Bob Azmoun, Craig Woody ( BNL ) Nikolai Smirnov ( Yale University )"— Presentation transcript:

1 P HOTON Y IELD DUE TO S CINTILLATION IN CF4 Bob Azmoun, Craig Woody ( BNL ) Nikolai Smirnov ( Yale University )

2 Motivation CF4 good radiator for Cherenkon light production (high refraction index, low chromatic dispersion, high transmission properties in the far UV). In a combination with CsI-based UV-photons detectors GEM detectors allows to realize these ideas (windowless). { A. Breskin group pioneer job }. But CF4 has been known as a good scintillation gas ( UV peak around 160 nm) {A.Pansky, A.Breskin, A.Busulutskov, R.Chechik, V.Elkind, J.Va ’ vra mesurements } Detector simulations and proposals for future (and today) set-ups have to include scintillation light production. So, we decided to use triple GEM with CsI to measure CF4 scintillation production once more.

3 The PHENIX Hadron Blind Detector (HBD) Proximity Focused Windowless Cherenkov Detector Radiator gas = Working gas Gas volume filled with pure CF 4 radiator 24 Triple GEM Detectors (12 modules per side) Area = 23 x 27 cm 2 Mesh electrode Top gold plated GEM for CsI Two standard GEMS Kapton foil readout plane One continuous sheet per side Hexagonal pads (a = 15.6 mm) Cherenkov blobs e+e+ e-e-  pair opening angle ~ 1 m

4 ALICE VHMPID variant, GEANT Simulation Y Z X 50 cm AeroGel, 10cm UV Mirror, spherical shape in ZY Double sided Read-out plane Triple GEM foils with CsI CaF2 Window C4F10 gas CF4 gas Particle track & UV photons R position: ~450 cm. Bz: 0.5 T Detector response: GEANT hits (π+, Pt~10. GeV/c; local coordinate system, cm) UV photoelectrons from “CF4 + Mirror” side UV photoelectrons from “C4F10 + Window” side MIP

5 Pb+Pb “ central ” HIJING event, one VHMPI Detector response ( “ slow ” simulator and reconstruction) X - MIP position - Track “reflection” from mirror; “circle center” - Photo-electrons from “bottom” gas UV light + window. Red circle – track has hits in TPC - Photo-electrons from “top” gas UV light + mirror green means Sc. Light from CF4

6 CF4 scintillation data, from NIM 354, (1995), 262; Pansky, Breskin, … Va ’ vra. E , ev N of UV photons / MeV / 4π Two approximations were used (MIN, MAX) in simulation for the variant with spherical mirror.

7 S ET -U P : “S CINTILLATION C UBE ” Signal: SBD  -trigger Signal: GEM pulse HV: Mesh/GEM HV: SBD CF4 Flow control SS Cubical Vessel Gas Analyzer Scintillation Light Collimated  -source (Am-241) Surface Barrier Det. (SBD) (  -trigger) Bubbler 3x3 cm Mesh &Triple GEM Stack/ 7 electrode volt. divider Plunger (y) Plunger (x) Fe55 (GEM abs. gain) Pressure Gauge CsI Photocathode

8 Absolute Quantum Efficiency of CsI photocathodes CsI PMT Comparison of our CsI photocathodes with a calibrated CsI PMT Good quality CsI photocathodes are now being made at Stony Brook Stack with Au coated GEM foil for depositing CsI photocathode VUV Spectrometer Scint. peak  160nm QE=27.5%

9 MAXIMIZING PE COLL. EFF. +0.1kV/cm

10 Gas Amplification Of GEM Detector Monitored gain of GEM through-out measurement, every hour or so. Gain ~ 7860

11 MC simulation Alpha Path Length

12 dE/dX for Alpha particles in CF4. -- SBD measurements in vacuum and gas -- Energy v Range published data

13 Preliminary result for CF4

14 STILL TO DO … Study ( measure ) systematic errors Measure abs. pe coll. Efficiency. Results with gases of know scintillation photon yield (Ar, CH4, mixtures) Try interesting mixtures such as Ar-CF4. More data in the report for IEEE meeting (November) Preliminary result – 180 +/- 20(?) UV photons / MeV / 4π


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