Beam test of scintillator strips

Miho NISHIYAMA

Shinshu University

・ scintillator strip calorimeter・ Kuraray scintillator strips and KNU extruded・ the result of DESY beam test・ KEK beam test・ results・ conclusion and plan

Scintillator strip

4.5cm

1cmMPPC

・ sampling calorimeter scintillator strips ＋ W

・ MPPC : light sensor

・ PFA requires scintillator fine segmented. → We need 10M scintillator strips. Production cost of scintillator strips must be cheap.

Thickness ： 0.3cm

Scintillator strip calorimeter

Comparison of scintillator strip

Method Extruded Casting

Production Extrusion Casting

and machining

Character Fiber hole and reflector (TiO2)

are made at the same time.

High accuracy of fiber hole

Problem Accuracy of fiber hole expensive

Company Misung Chemical Company and Kungpook National University

Kuraray

Beam position (mm)

Sig

nal (

AD

C c

ount

s) Casting reflector film Extruded 　 TiO2

Uniformity

Layer #

Strip #

CastingReflector film

ExtrudedTiO2

The result of DESY beam test

Response of MIP

2007 spring…Extruded scintillator strips ・ Light yield is low.・ Uniformity is bad.

Read out : fiber

Signal

(ADC counts)

Fiber – MPPC bad matching

Fiber

Sensitive surface of MPPC

extruded

・ Some extruded scintillator strips have too big fiber hole. 　　　　　　　 ・ Sometimes fiber holes aren’t correctly centered. 　　 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

Extruded scintillator strips

Too big fiber hole

The objective of KEK beam test

• We’ll use extruded scintillator strips at FNAL beam test in this summer. So we need them because their cost of production is cheap.

• Extruded scintillator strips have some problems.

position and size of fiber hole

Beam test with using carefully chosen extruded scintillator strip was carried out and compared with Kuraray.

KEK Fuji beam line・ Electron beam・ This beam is made form bremsstrahlung photons from KEKB ring・ Beam spot size: ~ 3cm x 4 cm・ Beam energy : 3 GeV ・ Rate: 15Hz @ 3 GeV

beam

Setup

Semiconductor Tracker(borrowed by ATLAS group) 12cm×6cm　　 Resolution 　　 vertical : 23μm 　　 horizontal: 580μm

Veto counter

Beam e-

Scintillator Fiber Tracker

Trigger countersMovable stage

Scintillator strips

scintillator

Beam e-

Semiconductor Tracker

Scintillator Fiber Tracker

Scintillator strips

Movable stage

Veto counter

Scintillator

Setup of side view

A B C D E F

beam

Scintillator Strips

Method Read-

out

Cover Thickness(mm)

A1

Extruded

Fiber

TiO2

3

No fiber !

A2 good positioning

B1

Reflector

big hole

B2 matched hole

C1 Direct TiO2

D

KurarayDirect

Reflector

2E

3F Fiber reference

• 8 layers with different types of strips• 4 same type strips per one layer

MIP selection 　

MIP selected strip

spacer

Only pedestal signal

For the selected strip, MIP event must satisfy following conditions: ・ In the same layer, strips show the pedestal signal but the selected strip.

・ In the front and the rear layer, the strips at same position of the selected strip show the MIP signal. 　

MIP signal

e-

All collected events MIP events

Response for MIP

extruded TiO2

No fiber

extruded TiO2

good matching

extrudedreflectorbad matching

extrudedreflector good matching

extruded TiO2

Kurarayreflector

Kurarayreflectorthickness:2mm

Kurarayreflector

reference

Num

ber

of e

vent

s (lo

g sc

ale)

Signal (ADC counts)

0 5000 0 5000 0 5000

0 0 0 0

0

5000 5000 5000 5000

5000

Response for MIPVariation of strip by strip

Num

ber

of e

vent

s (lo

g sc

ale)

Signal (ADC counts)

All collected events MIP events

Extruded scintillator strip ＋ reflector film good matching

These plots show the variation of strip by strip is big.

Uniformity

extruded TiO2

No fiber

extruded TiO2

good matching

extruded reflector bad matching

extruded reflectorgood matching

extruded TiO2

Kuraray reflector 　thickness:2mm

Kurarayreflector

Kuraray reflector

reference

Beam position (mm)

Sig

nal (

AD

C c

ount

s)

Beam position (mm)

Sig

nal (

AD

C c

ount

s)Uniformity

Variation of strip by strip

Extruded scintilattor strip ＋ reflector film good matching

These plots show the variations of the uniformity aren’t so big. However light yields aren’t same.

Conclusion

• The position of fiber and MPPC is important.

• Reflector film works better than TiO2 .

⇒ We asked KNU to make extruded scintillator

　　　 with the precise size of fiber hole and position

without TiO2 .

Plan

• More detail analysis about KEK beam test is neccesary.

• In this summer, FNAL beam test will be carried out using improved extruded scintillator strips.

Does direct light cause bad uniformity?

1mm

1mm

Direct light 100%

Direct light 25%

1mmφ

Sig

na

l (A

DC

cou

nts

)

Beam position (mm)

Extruded TiO2

Extruded TiO2

Good matching

Setup

PMT

Discriminator Gate Generator

90SrMPPC

ADC

(Vbias = 76.5 [ V])

Trigger scintillator

Thermostatic chamber (25 )℃

Extruded with TiO2

Collimator with2 mmhole

Signal input

Gateinput

AMP (x63)

72 [ns]

Position of-ray source

×x mm

MPPC

57mm

Measurement of 3 types

1mmφ 1mmφ

White paint to shield direct light

KIMOTO reflector to shield direct light

Scintillator with TiO2

Nothing to shield direct light

Result of measurementFiber : 43mmFiber : 57mm ＋ KIMOTO reflectorFiber : 43mm ＋ paint

MPPC side

Conclusion

• Direct light causes bad uniformity.

　→ We have the plan

to use the coupler

as the left figure shows.

Using this, direct light is

shielded and the fiber

position becomes stable.

Back up

Extruded scintillator strip with a fiber hole （ A,B ）

A1 A2

matched hole B2

bigger hole B1

Type : A covered with TiO2 A1 : fiber - MPPC bad matching A2 : fiber – MPPC good matching

Type : B covered with KIMOTO reflector film B1 : bigger hole B2 : matched hole

MPPCsensitive surface

Scintillator Assembly

scintillator strips 3mm

black sheet

KIMOTO reflector film

frame

frame

spacer

9 strips for a layer 12cm

9cm

FCBWith MPPC

4.5cm

4.5cm

0.4cm1cmThickness 0.3cm

Response for MIP(strip1) All collected events MIP events

extruded TiO2

No fiber

extruded TiO2

extrudedreflector

extrudedreflector

extruded TiO2

Kurarayreflector

Kurarayreflector thickness:2mm

Kurarayreflector

reference

Num

ber

of e

vent

s (lo

g sc

ale)

Signal (ADC counts)

All collected events MIP events

extruded TiO2

No fiber

extruded TiO2

extrudedreflector

extrudedreflector

extruded TiO2

Kurarayreflector

Kurarayreflectorthickness:2mm

Kurarayreflector

reference

Num

ber

of e

vent

s (lo

g sc

ale)

Signal (ADC counts)

Response for MIP(strip3)

All collected events MIP events

extruded TiO2

No fiber

extruded TiO2

extrudedreflector

extrudedreflector

extruded TiO2

Kurarayreflector

Kurarayreflectorthickness:2mm

Kurarayreflector

reference

Num

ber

of e

vent

s (lo

g sc

ale)

Signal (ADC counts)

Response for MIP(strip4)

Response Uniformity 　 (strip1)

extruded TiO2

No fiber

extruded TiO2

extruded reflector

extruded reflector

extruded TiO2

Kuraray reflector 　thickness:2mm

Kurarayreflector

Kuraray reflector

reference

Beam position (mm)

Sig

nal (

AD

C c

ount

s)

Response Uniformity (strip3)

extruded TiO2

No fiber

extruded TiO2

extruded reflector

extruded reflector

extruded TiO2

Kuraray reflector 　thickness:2mm

Kurarayreflector

Kuraray reflector

reference

Beam position (mm)

Sig

nal (

AD

C c

ount

s)

Response Uniformity (strip4)

extruded TiO2

No fiber

extruded TiO2

extruded reflector

extruded reflector

extruded TiO2

Kuraray reflector 　thickness:2mm

Kurarayreflector

Kuraray reflector

reference

Beam position (mm)

Sig

nal (

AD

C c

ount

s)