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 extrusion is easy to make thin 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

Die and Materials Polystyrene : 3 kg PPO : 1.3 % POPOP : 0.03% Die profile 4cm 1cm 2mm 1.2 mm 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. Reference samples Polysyrene bar New samples

Scintillator test setup FAN IN-OUT Logic unit 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 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

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

Light Yield Measurement cm 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