PENGEMBANGAN DETEKTOR SINAR-X BERBASIS FOTOTRANSISTOR DEVELOPMENT OF PHOTOTRANSISTOR BASED X-RAY DETECTOR

Ramacos Fardela, Prof. Drs. Kusminarto

2014 | Tesis | S2 Ilmu Fisika

Interaksi sinar-x dengan materi dapat menghasilkan gejala fluoresensi yang mengemisikan cahaya tampak. Fenomena ini dimanfaatkan untuk merancang detektor sinar-x berbasis fototransitor dengan menempelkan layar pemendar ZnS(Ag) di permukaan fototransistor yang disusun dalam rangkaian Darlington. Pengukuran daerah aktif detektor dilakukan dengan langkah mengkolimasi berkas sinar-x dari tabung pembangkit sinar-x Philips 2000 watt, 60 kV tipe PW 2215/20 NR 780026 dan mengukur tegangan keluaran detektor (Vout) setiap 1 mm perubahan posisi berkas secara horisontal maupun vertikal. Pengujian respon detektor terhadap perubahan intensitas sinar-x dilakukan dengan memvariasikan arus pada panel sinar-x sebesar 5, 10, 15, 20, 25, 30, 35 dan 40 dalam mA. Berdasarkan hasil eksperimen menunjukkan bahwa rangkaian Darlington dapat diterapkan untuk merancang detektor sinar-x berbasis fototransistor. Daerah aktif detektor yang disinari sinar-x diperoleh sebesar (3,5±0,5) mm horisontal dan (3,3±0,5) mm arah vertikal. Hasil menunjukkan bahwa terdapat hubungan linear antara tegangan keluaran detektor yang didekatkan dengan bahan fluoresensi Zns(Ag) terhadap perubahan intensitas sinar-x, ditunjukkan oleh koefisien korelasi R 2 = 0.99. Sensitivitas detektor didapatkan sebesar 4,0 × 10 -2 mV per cpm.

X-ray interaction with matter can produce phenomenon of fluorescence that emits visible light. This phenomenon was exploited to design an x-ray detector based on phototransistor by attaching a screen ZnS(Ag) on the surface of the phototransistor which is arranged in a Darlington circuit. Detection of active region of detector was done by collimating of x-rays beam from the x-ray generator tube Philips 2000 watts, 60 kV type PW 2215/20 NR 780 026 and measure the detector output voltage (Vout) at one millimeter change in x-ray beam position horizontally and vertically. Testing the detector response to changes in the intensity of x-rays was done by varying the current by 5 10, 15, 20, 25, 30, 35 and 40 mA in the x-ray panel. The experimental results showed that the Darlington circuit can be applied to design the detector of x-ray based on phototransistor. The active region of the detector was illuminated by x-rays obtained by (3,5±0,5) mm horizontally and (3,3±0,5) mm vertically. The results show that there is a linear relationship between the change in the intensity of x-ray detectors with voltage output phototransistor when was closed with fluorescence materials ZnS(Ag), the linearity coefficient was R 2 =0.99. Sensitivity of detector was obtained to be 4,0 × 10 -2 mV per cpm.

Kata Kunci : Detektor, fototransistor, Sinar-X, Layar ZnS(Ag)