4 separation confirmed Cherenkov photon “K”4.0GeV 4.0GeV Aerogel radiator n=1.05 Position sensitive PD with B=1.5Tesla 200mm R&D project since 2000 Crack-free large sample has been made refractive index control n =1.050 n = 0.0003 index deviation from average 110x110x20mm3 150x150x20mm3 1.045 1.055 1.050 1.062 A Study of Proximity Focusing RICH with Multiple Refractive Index Aerogel Radiator1I. Adachi, 2I. Bertović, 3K.Fujita, 4T. Fukushima, 2A. Gorišek, 3D. Hayashi, 3T. Iijima, 3K.Ikado, 5M.Iwabuchi, 4H. Kawai, 6,2S. Korpar, 3Y. Kozakai, 7,2P. Križan, 4A. Kuratani, 8T. Matsumoto, 3Y. Mazuka, 8T. Nakagawa,1S. Nishida, 5S. Ogawa, 2R. Pestotnik, 8T. Seki, 8T. Sumiyoshi, 4M. Tabata, 1Y. Unno1:IPNS, KEK, Tsukuba, Japan / 2:J.Stefan Institute, Ljubljana, Slovenia / 3:Dept. of Physics, Nagoya Univ., Nagoya, Japan /4:Dept. of Physics, Chiba Univ., Chiba, Japan /5:Dept. of Physics, Toho Univ., Funabashi, Japan 6:Faculty of Chemistry and Chemical Engineering, Univ. of Maribor, Maribor, Slovenia 7:Faculty of Mathematics and Physics, Univ. of Ljubljana, Ljubljana, Slovenia / 8:Dept. of Physics, Tokyo Metropolitan Univ., Tokyo, Japanpresented byPeter Križan (firstname.lastname@example.org) Proximity Focusing RICH with Aerogel Radiator Performance Test at 2002 Beam Experiment • Developed for a new particle ID device in the Belle forward region • improve/K separation up to 4 at 4GeV/c • limited space • operational under 1.5 Tesla magnetic field • Key components • Hydrophobic aerogel with refractive index of ~1.050 as a Cherenkov radiator • Position sensitive photodetector with ~5x5mm2 pixel size • Electronics for read-out RICH prototype counter n=1.05 aerogel radiator =14mrad Npe = 6 typical event Hamamatsu Multi-anode Flat-Panel PMT(H8500) /K 4 separation at 4 GeV/c achieved with a prototype counter need more photoelectrons for a further improvement as well as for more robustness Belle detector HOW ? Concept Validation in Beam Innovative idea to Get More Photoelectrons w/o Degrading Resolution Employ multiple layers with different indices so that Cherenkov images from individual layers overlap on the photon detector. 4cm-thick single index aerogel Simple accumulation of aerogel layers allows to detect more Cherenkov photons, however it deteriorates overall resolution. 2001 sample n1 n2 sq(1p.e.) = 22 mrad Npe ~ 10.6 sq(track) = 6.9 mrad Focusing by 2cm+2cm aerogel (n1:1.047, n2:1.057) n1 n2 sq(1p.e.) = 14.4 mrad Npe ~ 9.6 sq(track) = 4.8 mrad n1<n2 Novel idea of dual radiator “focusing scheme” has been proven • Only possible because refractive index of aerogel radiator can be adjusted in the production • Require further improvement of aerogel transparency not only for n=1.050 but for other indices Progress in Aerogel Radiator Production Extension of the newconcept: multiple layer radiator With new aerogels provided, we have examined the performance by stacking more layers duringa 2005 beam test Transparency improvement for sampleswith n=1.040~1.060 High accuracy of index is advantageous for dual/multiple layer radiator configurations Transmission length at = 400nm more than doubled Transmission length at 400nm(mm) Comparison between single index and multiple radiator schemes(3.0 GeV/c pion beam) old synthesis method # of photoelectrons single photon resolution resolution per track |()-()|/(track) ~5.5 separation achieved for 4 GeV/c with Npe= 9.1 Measured index 4th Progress on aerogel optical quality has been examined in test beam 3rd best (track) = 4.2 mrad 2nd 4th Npe 3rd 2nd 1st 2005 sample ▲：single index layer ●：multiple layer ▲：single index layer ●：multiple layer 1st 2001 sample Significant increase of Npe observed for 2005 sample, while old sample gets saturated around Npe~4.5 We have succeeded in getting more Npe without an increase in the single photon uncertainty. radiator thickness(cm) Conclusions Additional feature: RICH+TOF In 2004 we have introduced and tested a new technique which uses multiple aerogel tiles with different indices so that Cherenkov photons can be imaged tooverlapping rings. With this configuration, we have demonstrated a 5.5 separation with ~9 photoelectrons in the 2005 beam test. Optical quality of aerogel tiles has been significantly improved. As a result, photoelectron yield has been doubled. The radiator size can be enlarged by 86% and crack free sample was obtained. We have tested additional time-of-flight capabilities of such a counter. Both Cherenkov photons from the aerogel radiator as well as from the PMT window can be used. The latter would allow to extend the PID capabilities of the counter to particles which are below the Cherenkov threshold in aerogel. Idea: Make use of the fast photon detectors and measure time-of-flight with Cherenkov photons from aerogel and from the PMT window Beam test data: 50ps resolution per single photon ~20ps per track 10mV ~38ps per track References T.Iijima et al., NIM A543(2001)321. T.Matsumoto, S.Korpar et al., NIM A521(2004)367. T.Iijima, S.Korpar et al., NIM A548(2005)383. I.Adachi et al., NIM A553(2005)146. P.Križan et al., physics/0603022, to be published in NIMA. The Cherenkov photons from the window: can be used for particles below the threshold in aerogel The separation in Belle should be even better: flight distance ~2m (instead of 0.7m in the beam test set-up). Separation of pions and protons at 2 GeV, flight distance 0.7m.