TOP counteroverview and issues

K. Inami (Nagoya university)

2008/7/3-4 2nd 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-

8.0GeVe+

3.5GeV

1.5T

Introduction TOP (Time Of Propagation) counter

Developing to upgrade the barrel PID detector For Super B factory

Lpeak~1035~36/cm2/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

Simulation2GeV/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: 255cmL x 40cmW x 2cmT

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 ~1

00ps fluctuation for TOP. Use dependence of Cherenkov angle

to correct chromaticity Focusing system to measure c

c y position Reconstruct ring image from 3D info

rmation (time, x and y).

Focus Mirror

))(

1(cos=)( 1

βλnλθ c

ー

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 obtaingood 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; <2m 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 gaugePin gaugeMirrorMirror

LensLens

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 lifetim

e test Multi-alkali without Al protection la

yer on MCP (option) 4 /K separation for 4GeV/c Improved efficiency (x1.6) Almost established production, but ne

ed 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 (20mmt)

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 counterTest counterBeam test

@ KEK PS 2 line 3 GeV/c beamin=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 (1mmt)

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.

optionK/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 productionPMT lifetime

Focusing + multi-alkali

2.5 sigma 4.0 sigma if improved eff.

PMT lifetime

Focusing + GaAsP 4.2 sigma

PMT productionPMT lifetime