R&D status of Scintillator

Youngdo OhKyungpook National University

Junsuk Suh, Youngdo Oh, Kihyun Cho, Donghee Kim : Kyungpook National UniversityIntae Yu : SungKyunKwan Univesity

Soobong Kim : Seoul National University

8th ACFA WorkshopDaegu, Korea

Current R&D Status

1. At first, the pure polystyrene bar was produced without PPO, POPOP

The mechanical process is established

2. At second, PPO and POPOP were mixed up with polystyrene The 1st scintillator was produced.

3. Light yield was measured and compared with reference scintillator

Component: Polystyrene pellets + Dopants (primary & secondary)

Dopants

• Primary dopants (blue-emitting) PT(p-Teraphenyl), PPO(2,5-biphenyloxazole) 1-1.5% (by weight) concentration

• Secondary dopants (green-emitting) POPOP(1,4-bis(5-Phenyloxazole-2-yl)benzene), bis-MSB(4-bis(2-Methylstyryl)benzene)

0.01-0.03% (by weight) concentration

Production : Extrusion extrusion is easy to make thin scintillator

Plastic Scintillator

Plastic Scintillator – how does it work ?

Excitation of bas plastic by radiation

Foster energy transfer ( resonant dipole-dipole interaction)

Emit UV ~340nm

Absorb UV photon

Emit blue ~400nm

10-8 m

10-4 m photon

photon

Detector (PMT, photo diode …. )

Base plastic

PPO (~1%)

POPOP(~0.05%)

Extrusion Process All the work is done at one facility → reduces costs By removing its exposure to another high temperature cycle → reduces hits history of the product → eliminates an additional chance for scintillator degradation

Die and Materials

4cm

1cm2mm1.2 mm

Die profile

Mixture of dopants

Polystyrene : 3 kg PPO : 1.3 % POPOP : 0.03%

First Batch from Misung chemical At first, We try to produce polystyrene bar without PPO and POPOP to make sure the chemical and mechanical process. TiO2 was coextruded to make reflector.

At 2005/5/17 , Misung launched extrusion for scintillator The first product had big groove die had minor problem At 2005/6/9 , the excellent bars were produced. At 2005/7/7, the 2nd bacth has PPO, POPOP.

Evolution

2nd Production PPO and POPOP were mixed up 110 cm bars were produced We produced this batch in air

Comparision of transparency

Referencesamples

Polysyrenebar

New samples

Oxidation made the sample opaquebecause of production in air.

Scintillator test setup

Typical cosmic ray From reference sample + WLS

FAN IN-OUT

Logicunit

Gate Generator

100 ns

Delay

VME readout

Disc

5 reference samples and new samples with the same geometrical shape and size were used to compare light yield

Preparation of test samples

Light Yield MeasurementTrigger : threshold = 100mV , Gate=150ns

New scintillator bars (5 samples)<ADC counts> = 236.8 25.1

Reference scintillator bars(5samples)<ADC counts> = 590.6 76.9

Relative Light Yield of new samplesshows 40.1% of reference samples

Reference sample

New sample

ADC counts

ADC counts

Light Yield MeasurementTrigger : random trigger (1000Hz) , Gate=150ns (amplifier used : x100 )

New scintillator bars (5 samples)<ADC counts> = 225.9 24.9

Reference scintillator bars(5 samples)<ADC counts> = 534.8 56.9

Relative Light Yield of new samplesshows 42.3% of reference samples

New sample

Reference sample

ADC counts

ADC counts

Trigger : random trigger (1000Hz) , Gate = 2 s (amplifier not used)

Light Yield Measurement

New scintillator bars (5 samples)<ADC counts> = 26.5 3.5

Reference scintillator bars(5 samples)<ADC counts> = 79.1 8.4

Relative Light Yield of new samplesshows 33.5% of reference samples

New sample

Reference sample

ADC counts

ADC counts

Light Yield Measurement

Pico ammeter is used

Relative Light Yield of new samples shows 36.6% of reference samples’ one.

Reference samples Average = 4.35 RMS = 0.39

New samples Average = 1.59 RMS = 0.18

A

Sample ID

Light Yield Measurement

A

cm cm

ARefernce sample

New sample

Summary and Plan

First Polystyrene bar produced with PPO and POPOP The mechanical process is established Light yield measued for new and reference samples new sample shows ~40% light yield of reference sample low light yield because of oxidation in air

To avoid oxidation, we need to change process under Nitrogen or vaccum

If we get good light yield, then we will change die to produce “thin” scintillator for tile calorimeter thickness : 3mm , width : 1cm