Abstract
In this study, a wavelength shifting fiber that shifts ultra-violet and blue light to green light was employed as a sensor probe of a fiber-optic Cerenkov radiation sensor. In order to characterize Cerenkov radiation generated in the developed wavelength shifting fiber and a plastic optical fiber, spectra and intensities of Cerenkov radiation were measured with a spectrometer. The spectral peaks of light outputs from the wavelength shifting fiber and the plastic optical fiber were measured at wavelengths of 500 and 510 nm, respectively, and the intensity of transmitted light output of the wavelength shifting fiber was 22.2 times higher than that of the plastic optical fiber. Also, electron fluxes and total energy depositions of gamma-ray beams generated from a Co-60 therapy unit were calculated according to water depths using the Monte Carlo N-particle transport code. The relationship between the fluxes of electrons over the Cerenkov threshold energy and the energy depositions of gamma-ray beams from the Co-60 unit is a near-identity function. Finally, percentage depth doses for the gamma-ray beams were obtained using the fiber-optic Cerenkov radiation sensor, and the results were compared with those obtained by an ionization chamber. The average dose difference between the results of the fiber-optic Cerenkov radiation sensor and those of the ionization chamber was about 2.09%.
Highlights
Cerenkov radiation is produced in a dielectric material when a charged particle passes through the medium with a velocity greater than the phase velocity of light in the same medium [1]
In order to characterize Cerenkov radiation generated in the wavelength shifting fiber (WSF) and a plastic optical fibers (POFs), spectra and intensities of Cerenkov radiation were measured with a spectrometer
A fiber-optic Cerenkov radiation sensor (FOCRS) was fabricated using a WSF to measure Cerenkov radiation induced by gamma-ray beams of a Co-60 therapy unit
Summary
Cerenkov radiation is produced in a dielectric material when a charged particle passes through the medium with a velocity greater than the phase velocity of light in the same medium [1]. In the case of the FOCRS including the POF and the optical fiber for transmission, the intensity of Cerenkov radiation has a peak at a wavelength of 510 nm. This discrepancy is caused by the attenuation characteristics of the optical fiber for transmission. The measured spectrum of Cerenkov radiation has a similar trend as the characteristic transmission of the optical fiber In this experiment, optical fiber for transmission with a length of 20 m was used, and the original wavelength of the Cerenkov radiation might be incorrectly obtained according to the transmission properties of the optical fiber. The light output of the WSF via the optical fiber for transmission was 22.2 times higher than that of the POF; here, the intensities were obtained by integrating the counts from 400 to 800 nm
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