In this study, prototype ultra-thin fiber-optic dosimeters were fabricated using organic scintillators, wavelength shifting fibers, and plastic optical fibers. The sensor probes of the ultra-thin fiber-optic dosimeters consisted of very thin organic scintillators with thicknesses of 100, 150 and 200 μm. These types of sensors cannot only be used to measure skin or surface doses but also provide depth dose measurements with high spatial resolution. With the ultra-thin fiber-optic dosimeters, surface doses for gamma rays generated from a Co-60 therapy machine were measured. Additionally, percentage depth doses in the build-up regions were obtained by using the ultra-thin fiber-optic dosimeters, and the results were compared with those of external beam therapy films and a conventional fiber-optic dosimeter.

The metrology and inspection of contact hole layers is an extremely complex task. At feature sizes below 45 nm, an aspect ratio higher than 1:10 is required. SEM metrology and electron beam defect inspection both face extreme difficulties due to the fact that the secondary electrons from the bottom of the contact holes are absorbed by the walls and do not reach the detector. In this paper, the pre-charging of a large area before taking images of the hole was explored. An understanding of the physics involved in contrast formation and optimization of the system setup may improve SEM imaging. Pre-charge and imaging were simulated using CHARIOT Monte Carlo software with varying pre-charge and observation conditions. It was found that at specific parameters in the e-beam setting, image contrast is sufficient for metrology and defect inspection. The simulations involved high aspect ratio contact holes without defects, as well as with two types of defects: the remaining under-etched layer at the bottom, and a particle defect at the bottom. The experimental results of the e-beam defect inspection and CD-SEM of the contact holes involving the flood beam are presented. The results of the simulation qualitatively agreed with the measured data.

We developed a multichannel all-in-one phantom dosimeter system composed of nine sensing probes, a chest phantom, an image intensifier, and a complementary metal-oxide semiconductor (CMOS) image sensor to measure the dose distribution of an X-ray beam used in radiation diagnosis. Nine sensing probes of the phantom dosimeter were fabricated identically by connecting a plastic scintillating fiber (PSF) to a plastic optical fiber (POF). To measure the planar dose distribution on a chest phantom according to exposure parameters used in clinical practice, we divided the top of the chest phantom into nine equal parts virtually and then installed the nine sensing probes at each center of the nine equal parts on the top of the chest phantom as measuring points. Each scintillation signal generated in the nine sensing probes was transmitted through the POFs and then intensified by the image intensifier because the scintillation signal normally has a very low light intensity. Real-time scintillation images (RSIs) containing the intensified scintillation signals were taken by the CMOS image sensor with a single lens optical system and displayed through a software program. Under variation of the exposure parameters, we measured RSIs containing dose information using the multichannel all-in-one phantom dosimeter and compared the results with the absorbed doses obtained by using a semiconductor dosimeter (SCD). From the experimental results of this study, the light intensities of nine regions of interest (ROI) in the RSI measured by the phantom dosimeter were similar to the dose distribution obtained using the SCD. In conclusion, we demonstrated that the planar dose distribution including the entrance surface dose (ESD) can be easily measured by using the proposed phantom dosimeter system.

-A fiber-optic beta/gamma dual detector system with two types of sensing probes was fabricated to detect the beta-and gamma-rays simultaneously. As scintillators of the sensing probe type 1, two different inorganic scintillators, CaF2(Eu) and LYSO(Ce) crystals, were used to obtain the each scintillating efficiency with respect to betaand gamma-rays and the inherent energy spectra of radioactive isotopes. In the case of the sensing probe type 2, which is composed of two identical inorganic scintillators and a beta shielding material based on the lead, it could discriminate beta-and gamma-rays using a subtraction method. In conclusion, we demonstrated that the proposed fiber-optic beta/gamma dual detector could measure and discriminate beta-and gamma-rays using both energy spectroscopy and subtraction method.Key Words : Fiber-optic detector, Beta-ray, Gamma-ray, CaF2(Eu) cryatal, LYSO(Ce) cryatal

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