Sains Malaysiana 43(6)(2014): 953–958

 

UV-VIS Spectral Evaluation of CR-39 Detector Exposed with Diagnostic Dosage

(Penilaian Spektrum UV-Vis Pengesan CR-39 Terdedah dengan Dos Diagnostik)

Z. NUR SHA’DAH*1, S.M. ISKANDAR1, A.R. AZHAR1, M.J. SUHAIMI1, R. NUR LINA1 & M.K. HALIMAH2

1School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia

 

2Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia

 

Received: 3 November 2013/Accepted: 28 December 2013

 

ABSTRACT

The effects of the X-ray irradiation and chemical etching on the physical and optical properties of CR-39 plastic detectors were investigated for different doses of X-ray. CR-39 detectors were etched in the solution of the 3 M of NaOH after irradiation for revelations of the track. The tracks formed on CR-39 either by irradiated X-ray or due to the effect of environment. The changes in the thickness after exposed have significant decrease in 60 kVp and started to increase in range of 70 kVp up to 100 kVp due to the formation of oxidation layer on surface by free radicals. The optical band gaps before etching and after etching were determined by using Ultraviolet-visible (UV-Vis) spectroscopy. The optical band gap is attributed to the indirect transition due to its amorphous nature which is significantly decline trend energy in increase of the energy fluence of radiation. The Urbach’s energy, is defined as the width of the tail localized states in the forbidden band gap which change increment trend as increase in dose delivered due to the distortion structure of the CR-39 in terms of the electron charges in valences electron hence attributes to the induced modification of angle bond between the neighboring atoms.

 

Keywords: CR-39; optical band gap; X-ray irradiation

 

ABSTRAK

Kesan sinar-X pada beberapa pengesan plastik CR-39 dan punaran kimia telah dikaji dalam dos sinar-X yang berbeza dalam aspek perubahan sifat fizikal dan sifat optik. CR-39 terpunar dalam cecair NaOH 3 M selepas sinaran untuk pendedahan runut terbentuk pada CR-39 sama ada oleh sinaran-X atau kerana kesan alam sekitar. Perubahan ketebalan pendedahan mempunyai peningkatan penurunan yang beerti pada 60 kVp dan memulakan peningkatan dalam julat 70kVp sehingga 100 kVp ekoran daripada pembentukan lapisan pengoksidaan di permukaan oleh radikal bebas. Jurang jalur optik sebelum dan selepas punaran telah ditentukan dengan menggunakan spektrofotometer Ultralembayung-nampak (UV-Vis) yang dikatakan oleh peralihan secara tidak langsung disebabkan sifat amorfus yang ketara menolak trend tenaga di dalam peningkatan fluensi tenaga radiasi. Tenaga Urbach, ditakrifkan sebagai hujung lebar keadaan setempat dalam jurang jalur yang terlarang yang menukar trend kenaikan sebagai peningkatan dalam dos dihantar disebabkan oleh struktur herotan CR-39 dalam jangka caj elektron dalam elektron valen dan mengakibatkan pengubahsuaian teraruh sudut ikatan di antara atom jiran.

 

Kata kunci: CR-39; jurang jalur optik; sinar-X

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*Corresponding author; email: shaadahzainuddin@yahoo.com