TOP counter overview and issues K. Inami (Nagoya university) 2008/7/3-4 2 nd open meeting for proto-collaboration - Overview - Design - Performance - Prototype construction - Summary

2008/7/3-4 2nd open meeting for proto-collaboration 2 Side view of Super Belle detector 2.6m 1.2m e - 8.0GeV e + 3.5GeV 1.5T Introduction TOP (Time Of Propagation) counter Developing to upgrade the barrel PID detector For Super B factory L peak ~10 35~36 /cm 2 /s, 20~100 times higher than present Need to work with high beam BG To improve K/  separation power Physics analysis B   /K , , K etc. Flavor tag Full reconstruction Target; 4  for 4 GeV/c

2008/7/3-4 2nd open meeting for proto-collaboration 3 TOP counter Cherenkov ring in quartz bar Reconstruct ring image using ~20 photons on the screen reflected inside the quartz radiator as a DIRC. Photons are detected with photon detectors. Different ring image for the pion and kaon of the same momentum Need large screen...

2008/7/3-4 2nd open meeting for proto-collaboration 4 TOP counter 2D position information  Position+Time Compact detector! Linear array PMT (~5mm) Time resolution  ~40ps ~2m KK Simulation 2GeV/c,  =90 deg. ~200ps Different opening angle for the same momentum  Different propagation length(= propagation time) + TOF from IP works additively.

2008/7/3-4 2nd open meeting for proto-collaboration 5 Baseline design Quartz: 255cm L x 40cm W x 2cm T Focus mirror at 47.8deg. to reduce chromatic dispersion Multi-anode (GaAsP p.c.) MCP-PMT Linear array (5mm pitch), Good time resolution (<~40ps)  Measure Cherenkov ring image with timing information MCP-PMT TTS~35ps

2008/7/3-4 2nd open meeting for proto-collaboration 6 Chromatic dispersion GaAsP photo-cathode Higher quantum-efficiency at longer wavelength → less chromatic error Multi-alkali p.c. + cut filter (option) Light propagation velocity inside quartz Photon sensitivity at longer wavelength shows the smaller velocity fluctuation. Variation of propagation velocity depending on the wavelength of Cherenkov photons

2008/7/3-4 2nd open meeting for proto-collaboration 7 Focusing TOP Remaining chromatic effect makes ~100ps fluctuation for TOP. Use dependence of Cherenkov angle to correct chromaticity  Focusing system to measure  c   c  y position Reconstruct ring image from 3D information (time, x and y). Focus Mirror Side view Mirror image

2008/7/3-4 2nd open meeting for proto-collaboration 8 Focusing TOP (2)  c ~12mrad over sensitive range   y~20mm (~quartz thickness) We can measure dependence and obtain good separation even with narrow mirror and readout plane, because of long propagation length. Not need focusing block Not need fine readout channels 1850mm Virtual readout screen 22mm x 5mm matrix Focusing mirror  c ~12mrad

2008/7/3-4 2nd open meeting for proto-collaboration 9 Performance Focusing type + GaAsP photo-cathode >400nm filter, Correction Eff.=35% 4.2  K/  for 4 GeV/c,  =70 ﾟ

2008/7/3-4 2nd open meeting for proto-collaboration 10 TOP module A module supporting quartz and PMT Quartz radiator Support by aluminum honeycomb box Black box MCP-PMT Assemble with front-end elec. Connect elec. part to honeycomb Not glue PMT with quartz Prototype construction 1st step) quartz 1m (forward, backward part) By the end of June  Beam test 2nd step) quartz 2m + focus mirror By the end of December

2008/7/3-4 2nd open meeting for proto-collaboration 11 Quartz radiator Size; 915 x 400 x 20 mm Flatness; <2  m Roughness; <0.5nm By Okamoto optics work, inc. Support by Aluminum honeycomb panel 1cm thickness With plungers Keep quartz in air ~1kg/plunger on honeycomb ~2.5kg/plunger on side panel

2008/7/3-4 2nd open meeting for proto-collaboration 12 Focusing mirror Spherical mirror (R=5m) Check peak position of spherical mirror wrt. quartz edge By 3D measurement system at Nagoya univ. 0.33±0.30±0.20mm outside from bar edge Acceptable in simulation Cross check by interferometer in Okamoto optics work, inc. Pin gauge Mirror Lens Focusing mirror 2cm 40cm Spherical mirror (R=5m)

2008/7/3-4 2nd open meeting for proto-collaboration 13 PMT box MCP-PMT 27.5x27.5 mm square By Hamamatsu photonics Multi-alkali p.c.  beam test GaAsP p.c.  lifetime test PMT module HV divider AMP + CFD No CFD part for beam test PMT box 13 modules <40ps TTS for single photon Support modules and filters Attach to quartz box

2008/7/3-4 2nd open meeting for proto-collaboration 14 Photon detector; main issue Photo-cathodes of MCP-PMT Multi-alkali (bi-alkali); OK. Almost established production Confirmed enough lifetime GaAsP; in progress Better efficiency at longer wavelength Need more production R&D and lifetime test Multi-alkali without Al protection layer on MCP (option)  4   /K separation for 4GeV/c Improved efficiency (x1.6) Almost established production, but need some modification to improve lifetime (3-layer MCP, operation with lower gain, etc.) Al layer

2008/7/3-4 2nd open meeting for proto-collaboration 15 Summary Baseline design Focusing system To correct Chromatic effect with narrow mirror (20mm t ) GaAsP photo-cathode MCP-PMT Prototype shows the enough performance TTS = 35ps for single photon, High Q.E. (>40% at 500nm) Performance; >4  for 4GeV/c Prototype construction is in progress. Quartz bar + support structure Focusing mirror  Need to measure the TOP performance MCP-PMT + front-end elec. Issues MCP-PMT; Need better photon efficiency Need help, DAQ electronics (high precision TDC;  ~10ps) Structure construction, Software,...

2008/7/3-4 2nd open meeting for proto-collaboration 16 Test counter Beam KEK PS  2 line 3 GeV/c   beam  in =  in =90 degree Clear ring image Reasonable time resolution Enough bar quality 1mm pitch readout

2008/7/3-4 2nd open meeting for proto-collaboration 17 Geometry 18 counters in r-  Al wall (1mm t ) Quartz  10% dead space in  Maybe need to be overlapped layout Need to locate support structure in narrow space ~20mm between quartz and outer structure Overlapped layout

2008/7/3-4 2nd open meeting for proto-collaboration 18 Performance Focusing type + Multi-alkali >350nm filter, Correction Eff.=60% 3.5  K/  for 3 GeV/c,  =70 ﾟ Because of complicated ring image

2008/7/3-4 2nd open meeting for proto-collaboration 19 TOP configuration summary Focusing type can reduce the dead space and remove middle PMT. option K/pi separation performance at 70 deg, 4GeV/c issues 3 readout + multi-alkali 2.8 sigma(Make prototype) 3 readout + GaAsP 3.5 sigma PMT production PMT lifetime Focusing + multi-alkali 2.5 sigma  4.0 sigma if improved eff. PMT lifetime Focusing + GaAsP 4.2 sigma PMT production PMT lifetime