The sensitivity of low-loss perfluorinated polymer optical fiber (PF-POF) to gamma radiation is investigated for on-line
radiation monitoring purposes. The radiation-induced attenuation (RIA) of a commercial PF-POF based on Cytop material
is measured in the visible spectral region. The fiber RIA shows strong wavelength dependence with rapid increase towards
the blue side of the spectrum. The wide range of radiation sensitivities is available via careful selection of appropriate
monitoring wavelength. The accessible sensitivities span from 1.6 ± 0.2 dBm-1/kGy measured at 750 nm to
18.3 ± 0.7 dBm-1/kGy measured at 420 nm. The fairly high radiation sensitivity as well as its wide tunability makes the
fiber a promising candidate for a broad range of applications.
Two Organic Photovoltaic devices having a photoactive layer containing Poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5- (4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM, 99%), and the layer sequences – glass/ITO/ZnO/PAL/PEDOT:PSS/Ag/encapsulation were non-destructively investigated by diffuse optical spectral reflectance, THz spectroscopy and THz imaging. The proposed methods proved to be powerful tools to support quality assurance in organic solar cells development, facilitating both the localization of manufacturing defects and the device degradation, as they are combined with “classical” evaluation means.
In this paper, we report the results concerning electron beam irradiation of mid-IR windows and mid-IR detectors for possible use in trace gas detection systems, in the 1 μm to 5 μm spectral range under ionizing radiation conditions. Four windows materials (CaF2, BaF2, ZnSe, and sapphire) for the mid-IR were tested as they were exposed to electron beam irradiation at a dose rate of 4 kGy/min, for doses from 0.5 kGy to 2.2 kGy. Two IR detectors (photoconductive – PbSe, photovoltaic – InAs) were subjected to the same type of irradiation at dose rate of 4 kGy/min, in three subsequent exposures, for a total dose up to 6.8 kGy. Before the irradiation and after each irradiation step the windows were measured as it concerns the spectral optical transmittance, spectral optical diffuse reflectance, and, in the THz range (0.06 THz – 3 THz), the dielectric constant and the refractive index were evaluated. THz imaging analysis of the irradiated samples was done. For the IR detectors we measured at different irradiation stages the spectral responsivity and the dark current. The most affected by electron beam irradiation was the CaF2 window, in the spectral interval 250 nm – 800 nm. The spectral transmittance of the four windows remained unchanged after their exposure to ionizing radiation in the near-IR and mid-IR. Noticeable variations of the spectral responsivity appeared upon electron beam irradiation in the case of the InAs detector.
In this paper, we present the first results regarding the on-line monitoring of gamma-ray exposure effects on a commercial multi-mode perfluorinated polymer optical fiber (PF-POF), type GigaPOF-50SR from Chromis Fiberoptics. Our focus was to evaluate on-line the radiation induced attenuation (RIA) over a wide spectral range (320 nm – 1700 nm), in order to assess the fiber’s radiation hardness and its possible use in radiation detection. An Ocean Optics QE65000 high sensitivity spectrometer and a StellarNet near-IR spectrometer were used to cover the spectral ranges 200 nm – 1μm and 900 nm – 1.6 μm, respectively. Electron paramagnetic resonance was used to monitor the recovery of the irradiation induced centers at room temperature. The study indicated that the optical fiber can be used as radiation monitor at low dose rates by measuring the attenuation in the UV, while higher dose rates irradiation can be observed by RIA monitoring at specific wavelengths in the visible spectral range.
We report the first demonstration of single-mode laser beam delivery in hollow-core waveguides (HCWs) operating in the 3.7-7.3 μm spectral range. We investigated the transmission properties of HCWs with 200 μm bore diameter and internal coatings properly designed to enhance the spectral response in the spectral range of 3-12 μm. We achieved single mode output throughout the 3.7-7.3 μm range. We measured a coupling efficiency < 90% and transmission losses as low as 1 dB, when using a 15 cm-long fiber at 3.7 μm under optimized coupling conditions between input beam and HCW.
A PMMA based plastic optical fibre sensor for use in real time radiotherapy dosimetry is presented. The optical fibre tip is coated with a scintillation material, terbium-doped gadolinium oxysulfide (Gd2O2S:Tb), which fluoresces when exposed to ionising radiation (X-Ray). The emitted visible light signal penetrates the sensor optical fibre and propagates along the transmitting fibre at the end of which it is remotely monitored using a fluorescence spectrometer. The results demonstrate good repeatability, with a maximum percentage error of 0.5% and the response is independent of dose rate.
The atmospheric aerosol particles have variable optical properties, depending on their composition and their size
distribution. The aim of this paper is to use six measured parameters with a Nephelometer, to derive optical properties of
sub-micrometric and micrometric particles. The analysis of the backscatter to total scattering ratio and the wavelength
dependence of particle scattering showed a daily and monthly variability, the ratio being bigger for the summer month
than the autumn month. This result can affect seasonal variation of radiative forcing at surface. The results were
compared with those obtained from sun - photometer data.