Development of a wavelength-separated type scintillator with optical fiber (SOF) dosimeter to compensate for the Cerenkov radiation effect.
Bottom Line: The scintillator of the current SOF dosimeter is a 1-mm diameter hemisphere.A dichroic mirror was used for separating input light signals.Individual signal counting was performed for high- and low-wavelength light signals.
Affiliation: Department of Medical Physics and Engineering, Graduate School of Medicine, Hokkaido University, N-15 W-7 Kita-ku, Sapporo Hokkaido, 060-8638, Japan email@example.com.Show MeSH
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Mentions: On the other hand, for the spectrum filtering technique, the possibility exists of efficiency change due to spectrum change that may occur by bending the optical fiber. To confirm the effect of optical fiber bending, wavelength spectra was measured at 180°, as shown in Fig. 5, with the optical fiber lopped five times (diameters 10, 15 and 20 cmφ) using probe #1 and the USB-2000 spectrometer (manufactured by Ocean Optics Ltd). The relative efficiency for the 10, 15 and 20 cmφ loops were 1.000 ± 0.0027, 1.005 ± 0.0026 and 1.007 ± 0.0025, respectively. Here, relative efficiency refers to the ratio of the signal value with and without bending of the optical fiber. The efficiency change due to bending an optical fiber seems thus not to be observed. Figure 9 shows the measured wavelength spectra of the scintillation and Cerenkov signals with and without bending using another scintillator-less probe. As shown in Fig. 9, both the scintillation and Cerenkov light spectrum are almost identical, even if the optical fiber was bent with 10 cmφ × 5 times. For practical usage, looping optical fiber with less than 10 cmφ diameter is rare; the efficiency due to bending will thus be negligible. The Cerenkov spectrum was different from that reported by Frelin et al. (2005) , indicating that attenuation of short wavelengths in the optical fiber might occur. However, calibration was performed including such an attenuation effect; influence to the dose evaluation seems therefore to be negligible for light attenuation in the fiber.Fig. 9.
Affiliation: Department of Medical Physics and Engineering, Graduate School of Medicine, Hokkaido University, N-15 W-7 Kita-ku, Sapporo Hokkaido, 060-8638, Japan firstname.lastname@example.org.