Development of TOP counter for Super B factoryTDC (ns) 6 gaussian fit. σ common = 82.ps TDC distribution (x=11.3mm) Test counter Quartz bar spec. Quartz : sprasil P20 (Synthetic fuzed

Development of TOP counterfor Super B factory

K. Inami (Nagoya university)

2008/3/19-20 Open meeting for proto-collaboration

- Introduction- Design study

- PMT property- Focusing system

- Prototype construction- Summary

2008/3/19-20 Open meeting for proto-collaboration 2

Side view of Super Belle detector

2.6m

1.2m

e-

8.0GeVe+

3.5GeV

1.5T

IntroductionTOP (Time Of Propagation) counter

Developing to upgrade the barrel PID detectorFor Super B factory

Lpeak~1035~36/cm2/s, 20~100 times higher than presentNeed to work with high beam BG

To improve K/π separation powerPhysics analysis

B ππ/Kπ, ργ, Kνν etc.Flavor tagFull reconstruction

Target; 4σ for 4 GeV/c


TOP counterCherenkov 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.

πK

x

y

θc = cos (1/nβ)

Quartz : n = 1.471 (@λ=390nm)

Φ

Different ring image for the pionand kaon of the same momentum

Need large screen...


TOP counter2D position information Position+Time

Compact detector!~400mm

Linear-array type photon detector

LX

20mm

Quartz radiator

x

y

zLinear array PMT (~5mm)Time resolution σ~40ps

~2m

12000

14000

16000

18000

20000

22000

24000

26000

28000

30000

-20 -10 0 10 20

TD

C (

ps)

X (cm)

Kπ

Simulation2GeV/c, θ=90 deg.

~200ps

Different opening angle for the same momentumDifferent propagation length(= propagation time)

+ TOF from IP works additively.


0

50

100

150

200

250

300

-100 -50 0 50 100x (mm)

TOP

(

ch/2

5ps)

2 3 4 5TDC (ns)

6 gaussian fit.

σcommon = 82.ps

TDC distribution (x=11.3mm)

Test counter

Quartz bar spec. Quartz : sprasil P20 (Synthetic fuzed silica,

made by shin-etsu co.) size : 1000mm 200mm 20mm surface : 0.5nm(rms), figure < 2μm squrness : < 0.3mrad, edge radius < 5μm polished by Okamoto optics work,inc

1000mm

PMT HPK R5900-U-L16

200mm

Test counterBeam test@ KEK PS π2 line

3 GeV/c π− beamθin=φin=90 degree

• Clear ring image

• Reasonable time resolution

• Enough bar quality

1mm pitch readout

2008/3/19-20 Open meeting for proto-collaboration 6IP

Forward Backward

Focus mirror(sphere, r=5000)

32.8o~123.5o

47.8o

R=1180z=1830 z=1070 z=-780

5mm

40cm

2cm

Baseline designQuartz: 255cmL x 40cmW x 2cmT

Focus mirror at 47.8deg. to reduce chromatic dispersion

Multi-anode (GaAsP) MCP-PMTLinear array (5mm pitch), Good time resolution (<~40ps)

Measure Cherenkov ring image with timing information

MCP-PMT


ChromaticityDetection time depending on the wavelength of Cherenkov photons

Worse time resolution→ Worse ring-image separation

Propagation velocity depending on λ in the quartz bar

12000

14000

16000

18000

20000

22000

24000

26000

28000

30000

-20 -10 0 10 20

TD

C (

ps)

X (cm)

300

400

500

600

16000 20000 24000 28000

TDC(ps)0

100

200

16000 20000 24000 28000

λ(nm

)

π, 2GeV/c, θ=90deg., ch=40


0

5

10

15

20

25

30

35

40 Bi-alkali

GaAsP

photon lambda(nm)

QE

(%)

300 400 500 600 700

Multi-alkali

GaAsP photo-cathode ( alkali p.c.)Higher quantum-efficiency at longer wavelength → less chromatic error

Chromatic dispersion

0.19

0.2

0.21

300 400 500 600 700Wave length (nm)

Gro

up v

eloc

ity (m

/ns) 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


GaAsP MCP-PMT developmentSquare-shape MCP-PMT with GaAsP photo-cathode is developed with Hamamatsu Photonics.

PrototypeGaAsP photo-cathode

Al protection layer

2 MCP layersφ10μm hole

4ch anodesSlightly large structure

Less effective area

Performance testTime resolution

22(effective area)27.5mm

1ch

2ch

3ch

4ch

Target structure

DISC

PLP PMT ATTN AMP DIV

TDC

ADCFILTER

BLACK BOXDISC

λ=407nmJitter～10ps

there 100mV

36dB

there 20mV

25ps/1bin

CAMAC

START

GATE

DISC


TDC

ADCFILTER

BLACK BOXDISC


there 100mV

36dB

there 20mV

25ps/1bin

CAMAC

DISC


TDC

ADCFILTER

BLACK BOXDISC


there 100mV

36dB

there 20mV

25ps/1bin

CAMAC

DISC


TDC

ADCFILTER

BLACK BOXDISC


there 100mV

36dB

there 20mV

25ps/1bin

CAMAC


TDC

ADCFILTER

BLACK BOXDISC


there 100mV

36dB

there 20mV

25ps/1bin

CAMAC

START

GATE


Wave form, ADC and TDC distributions for single photon

Enough gain to detect single photo-electronGood time resolution (TTS=35ps) for single p.e.

GaAsP MCP-PMT performance

Single p.e.0.5ns/div20mV/div

ADC

0

100

200

300

400

500

600

100 120 140 160 180/0.25pc

cou

nt

pedestal

single photon peak

Gain～0.64×106

Time

0

1000

2000

3000

-20 -10 20/25ps

cou

nt

0 10

TTS~35ps


Focus Mirror

y

PM

T

Focusing TOPRemaining chromatic effect makes ~100ps fluctuation for TOP.Use λ dependence of Cherenkovangle to correct chromaticityFocusing system to measure θc

λ θc y positionReconstruct ring image from 3D information (time, x and y).

Focus Mirror

))(1

(cos=)( 1

βλnλθ cー

Side view

Mirror image


Focusing TOP (2)Δθc~1.2mrad over sensitive λ range

Δy~20mm (~quartz thickness)We can measure λ dependence and obtaingood separation even with narrow mirror and readout plane, because of long propagation length.

Not need focusing blockNot need fine readout channels

1850mm

Virtual readout screen22mm x 5mm matrixFocusing

mirror

Δθc~1.2mrad


IP

Forward Backward


32.8o~123.5o

47.8o

R=1180z=1830 z=1070 z=-780

0

2

4

6

8

10

12

14

16

40 60 80 100 120polar angle (deg.)

Sep

arat

ion

pow

er (

σ)

2GeV/c3GeV/c4GeV/c

Focusing type + GaAsP photo-cathode>400nm filter, Correction Eff.=35%

4.2σ K/π for 4 GeV/c, θ=70ﾟ

Performance

90

92

94

96

98

100

40 50 60 70 80 90θ (deg.)

Effi

cien

cy (

%) 2.0GeV/c

3.0GeV/c4.0GeV/c

0

2

4

6

8

10

40 50 60 70 80 90θ (deg.)

Fak

e ra

te (

%)

2.0GeV/c

3.0GeV/c4.0GeV/c


Robustness against beam BGDegradation of ring image separation due to the BG photons from beam BGCurrent BG rate x 100 is acceptable.

compared to L=1034 level


Prototype construction

18 counters in r-φ

Al wall (1mmt)

Quartz

Geometry∼10% dead space in φ

Maybe need to be overlapped layoutNeed to locate support structure in narrow space

~20mm between quartz and outer structure

Overlapped layout


TOP module

A module supporting quartz and PMTQuartz radiator

Support by aluminum honeycomb boxBlack box

MCP-PMTAssemble with front-end elec.Connect elec. part to honeycomb

Not glue PMT with quartz

Prototype construction1st step) quartz 1m (forward, backward part)

By the end of June2nd step) quartz 2m + focus mirror

By the end of December

PMT

AMP+CFD

HV divider


Quartz supportSupport structure for 1mx40cmx2cm quartz

Honeycomb panel1cm thickness

PlungersKeep quartz in air~1kg/plunger on honeycomb

Al land is glued by araldite

~2.5kg/plunger on side panel

10mm

M4

Honeycomb

Plunger


Assemble stageFlatness and reflectance of quartz bar inside support structure

Measure laser position and intensity by CCD through quartz bar

Flatness; <100μm

CCDInternal reflection

Laser Support structure


Focusing mirrorCheck accuracy of mirror shape

Peak position of spherical mirror wrt. quartz edgeBy 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 gauge

MirrorMirror

LensLens

Focusing mirror

2cm

40cm

Spherical mirror (R=5m)


Photon detectorsGaAsP MCP-PMT

Basic performance; OK.Check QE distribution by moving stage

Good performance in recent sampleQE lifetime; shorter than multi-alkali p.c.

Multi-alkali photocathode with improved efficiencya) 3-layer MCP-PMT; test with BINPb) another configuration of Al protection layer

PD

MCP-PMT

SpotX

Y

Monochrometer

YH0053 YH0056 YH0057 YH0081

old new


Front-end electronicsHV divider + AMP + CFD

Constant fraction discriminator

Compact test module<8ps timing jitter

AMP testNeed low noise and suitable output voltageSome candidates (MMIC, discrete IC module, etc.)

CFD testWith MCP-PMTResult; 30ps resolution without correction

PMT module1st prototype will be ready soon.

5cm

PMT

AMP+CFD

HV divider

HV divider


SummaryR&D of TOP counter is in progress!Design studies

To suppress the influence of chromaticityGaAsP photo-cathode MCP-PMT

Prototype shows the enough performanceGain = 0.64x106, TTS = 35ps for single photonHigh Q.E. (>40% at 500nm)

Focusing systemNarrow mirror and narrow readout planeForm large virtual readout screen

Not need focusing block and fine PMT channels

Performance; >4σ for 4GeV/c

Prototype constructionQuartz bar + support structureFocusing mirror; enough accuracyMCP-PMT + front-end elec.

quartz bar 915x40x2cm


0

5

10

15

20

25

30

35

40 Bi-alkali

GaAsP

photon lambda(nm)

QE

(%)

300 400 500 600 700

Multi-alkaliPhoto-cathode of MCP-PMT

Multi-alkaliAlmost established productionEnough lifetime

GaAsPBetter efficiency at longer wavelengthNeed more production R&D and lifetime test

Multi-alkali without Al protection layer on MCP (option)

Better efficiency (x1.6)Almost established production, but need some modification to improve lifetime (3-layer MCP, operation with lower gain, etc.)

Possible configuration

GaAsPMCP-PMT


IP

Forward BackwardPMT

32.8o~123.5o

47.8o 1180mm

z=1830mm z=1070mm z=-780mm

0

2

4

6

8

10

12

14

16

40 60 80 100 120polar angle (deg.)

Sep

arat

ion

pow

er (

σ)

2GeV/c3GeV/c4GeV/c

90

92

94

96

98

100

40 50 60 70 80 90θ (deg.)

Effi

cien

cy (

%) 2.0GeV/c

3.0GeV/c

4.0GeV/c

0

2

4

6

8

10

40 50 60 70 80 90θ (deg.)

Fak

e ra

te (

%)

2.0GeV/c3.0GeV/c

4.0GeV/c

3-readout type + GaAsP photo-cathode>400nm filter, Correction Eff.=35%


Performance


0

2

4

6

8

10

12

14

16

40 60 80 100 120polar angle (deg.)

Sep

arat

ion

pow

er (

σ)

2GeV/c3GeV/c4GeV/c

IP

Forward Backward


32.8o~123.5o

47.8o

R=1180z=1830 z=1070 z=-780

Focusing type + Multi-alkali>350nm filter, Correction Eff.=60%


Performance

90

92

94

96

98

100

40 50 60 70 80 90θ (deg.)

Effi

cien

cy (

%) 2.0GeV/c

3.0GeV/c4.0GeV/c

0

2

4

6

8

10

40 50 60 70 80 90θ (deg.)

Fak

e ra

te (

%)

2.0GeV/c

3.0GeV/c4.0GeV/c

Because of complicated ring image


TOP configuration summary

Focusing type can reduce the dead space and remove middle PMT.

optionK/pi separation

performance at 70 deg, 4GeV/c

critical 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

Documents

Development of TOP counter for Super B factoryTDC (ns) 6 gaussian fit. σ common = 82.ps TDC distribution (x=11.3mm) Test counter Quartz bar spec. Quartz : sprasil P20 (Synthetic fuzed