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Beam test of low index sillica aerogel

Beam test of low index sillica aerogel. Yukiyoshi Kon RCNP, Osaka University. Collaboration meeting @ Tiwan 2008/5/2. Low reflective index silica aerogel was developed by Chiba University group. To use as AC veto Counter, we tested this sillica aerogel by beam at LEPS . 2008/4/21,22

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Beam test of low index sillica aerogel

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  1. Beam test of low index sillica aerogel Yukiyoshi Kon RCNP, Osaka University Collaboration meeting @Tiwan 2008/5/2

  2. Low reflective index silica aerogel was developed by Chiba University group. • To use as AC veto Counter, we tested this sillica aerogel by beam at LEPS . • 2008/4/21,22 • Tabata, Saito, Kawai, Chiba University, Kon • Detection efficiency and mean # of photoelectron was estimated about index n = 1.015, 1.0082 and 1.0027.

  3. Method to estimate efficiency • Aerogel Counter: • Cerenkov effect • Photomultiplier Emission of photoelectrons from cathode obey Poisson statistics. • Detection efficiency:

  4. Cerenkov counter(: C)’s signal is taken with S1, S2 coincidence trigger. • Beam is injected inside Cerenkov counter perfectly. • Pulse hight distribution obteined by ADC outputs forms Poisson distribution. C S1 S2 S1, S2: Scintillation counters C: Cerenkov Counter I. Adachi et al./Nucl. Instr. and Meth. in Phys. Res. A 355 (1995) 390-398

  5. Beam test Counter design Light guide box: width 125 x hight 260 x thickness 65 Covered by reflector Alminized mylar & Gore-tex sheet. 4 Photomultiplier: Fine mesh type (Hamamatsu Photonics H6614-70) Aerogel was arranged by hangging in midair by strings. TOF Wall C S3 Set up S1 • Beam: Converting LEP into e+e- shower by 10mm x 10mm lead sheet. • Trigger: Tag x !UP x (S1 x S2 x S3) • S1, S2: front Scintillation Counters, • S3: backward Scintillation Counter. S2 LEP Convertor

  6. Index and Reflector Scillica aerogel n = 1.0027 was first beam test in the world. But, Transmission was bad. 20 mm Threshold momentums 100 mm 100 mm

  7. Cerenkov angle • Cerenkov angle: • Beam: electron • In very low index point, Cerenkov angle is a few degrees. θ [rad.] n: smaller n = 1.0027, 1.0082, 1.015, etc. β

  8. Aerogel arangement Version A: 40 mm 65 mm 20 mm 100 mm e Emitted photon is larger than 40mm one. But path length is longer. Light‘s pass length is shorter. But emitted photon is less.

  9. Version B: Only n = 1.0027, mylar 40 mm e Cerenkov light mainly is ejected to forward direction. It is difficult to go out from aerogel in horizontal dirrection.

  10. Index dependence Analyzed event #: 10000 for all samples. n=1.0027 n=1.015 n=1.0082 Mylar, 40mm Pulse hight distribution was selected to get correct photoelectron event by TDC cut. 4 photomultiplier‘s event # was summed up. Photoelectron’s number became smaller, as soon as index was smaller.

  11. Estimation - The number of mean photoelectron and efficiency n=1.015 n=1.0082 n=1.0027 Pedestal 25794 All 40000 Npe = 0.191 Eff. = 0.355 Pedestal 13898 All 40000 Npe = 0.451 Eff. = 0.653 Pedestal 9163 All 39984 Npe = 0.640 Eff. = 0.771

  12. Pass length dependence 40mm 65mm Npe = 0.640 Eff. = 0.771 Npe = 0.994 Eff. = 0.899 Npe and efficiency was increased , as pass length longer.

  13. Difference of aerogel arrangemnt B A Npe = 0.191 Eff. = 0.355 Npe = 0.168 Eff. = 0.321 Npe and efficiency of version B was little worse.

  14. Difference of reflecting materials mylar Gore-tex Npe = 0.639 Eff. = 0.771 Npe = 1.061 Eff. = 0.913 Efficiency ofGore-tex counter was better - it’s suitable for random reflection in light guide box.

  15. Empty Counter Mylar Gore-tex Npe = 0.181 Npe = 0.014 • Little Cerenkov light was emitted • Air Cerenkov ? • Photon # was more than mylar. • Scintillation light from Gore-tex ?

  16. Summary Efficiency • We tested low index sillica aerogel with beam, and estimated detection efficiency. • For NTPC Experiment, counter coverd Gore-tex one is not suitable for e+e- beto counter because of over veto the hadron. • AC beto counter was exchanged to (n=1.0082, version B, mylar) from (n=1.01, version B, Gore-tex). • Efficiency should be rechaecked another method, beacause pedestal couldn’t from distribution perfectly. • - Fitting with poisson distribution conboluted gaussian function.

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