R&D status of Scintillator

R&D status of Scintillator 8th ACFA Workshop Daegu, Korea Youngdo Oh Kyungpook National University Junsuk Suh, Youngdo Oh, Kihyun Cho, Donghee Kim : Kyungpook National University Intae Yu : SungKyunKwan Univesity Soobong Kim : Seoul National University

Current R&D Status • 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

Plastic 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 – how does it work ? Excitation of bas plastic by radiation Base plastic 10-8 m Foster energy transfer ( resonant dipole-dipole interaction) PPO (~1%) Emit UV ~340nm 10-4 m photon Absorb UV photon POPOP(~0.05%) Emit blue ~400nm photon Detector (PMT, photo diode …. )

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

1.2 mm 2mm 1cm 4cm Die and Materials • 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 Oxidation made the sample opaque because of production in air. Polysyrene bar Reference samples New samples

FAN IN-OUT Disc Logic unit Gate Generator 100 ns Delay VME readout Scintillator test setup • 5 reference samples and new samples with the same geometrical shape and size were used to compare light yield Typical cosmic ray From reference sample + WLS

Preparation of test samples

Light Yield Measurement Trigger : threshold = 100mV , Gate=150ns New sample New scintillator bars (5 samples) <ADC counts> = 236.8  25.1 Reference scintillator bars(5samples) <ADC counts> = 590.6 76.9 ADC counts Reference sample Relative Light Yield of new samples shows 40.1% of reference samples ADC counts

Light Yield Measurement Trigger : random trigger (1000Hz) , Gate=150ns (amplifier used : x100 ) New sample New scintillator bars (5 samples) <ADC counts> = 225.9  24.9 Reference scintillator bars(5 samples) <ADC counts> = 534.8 56.9 ADC counts Reference sample Relative Light Yield of new samples shows 42.3% of reference samples ADC counts

Light Yield Measurement Trigger : random trigger (1000Hz) , Gate = 2 s (amplifier not used) New sample New scintillator bars (5 samples) <ADC counts> = 26.5  3.5 Reference scintillator bars(5 samples) <ADC counts> = 79.1  8.4 ADC counts Reference sample Relative Light Yield of new samples shows 33.5% of reference samples ADC counts

Reference samples Average = 4.35 RMS = 0.39 A New samples Average = 1.59 RMS = 0.18 Sample ID Light Yield Measurement Pico ammeter is used Relative Light Yield of new samples shows 36.6% of reference samples’ one.

A A cm cm Light Yield Measurement Refernce 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

R&D status of Scintillator