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We evaluated the radiation tolerance of volume holographic elements written in photo-thermo refractive glass. To do so these elements were exposed to Co60 gamma-radiation and 60 MeV protons. At 10 kGy dose levels a high stability has been observed. Our results confirm that such components can operate in a space radiation environment. [ABSTRACT FROM AUTHOR]

Presents a study that assessed the development of radiation-tolerant instrumentation data links that could be used in thermonuclear fusion experiments. Background on the digital optoelectronic serial data link for International Thermonuclear Experimental Reactor remote handling tasks; Discussion on radiation-hardened electronics; Analysis of the implementation of error-correction schemes.

Focuses on a study that tested a radiation-tolerant opto-electronic transmitter based on vertical-cavity surface-emitting lasers and dedicated driver electronics consisting of discrete components. Background and method; Irradiation results and discussion; Conclusion.

Focuses on a study which examined the wavelength division multiplexing (WDM) optical link for the thermonuclear fusion reactor instrumentation. Information on the force sensor based on multiplexed Fiber Bragg grating strain sensors; Details on WDM coupler behavior under radiation; Conclusion.

Presents information on a study which examined the effect of MGy dose level gamma-irradiation on the parameters of fibre Bragg gratings (FBG) intended for sensing applications. Properties of optical fibre sensors and FBG; Experimental details; Results and discussion; Conclusions.

A digital VCSEL driver has been designed, simulated and assessed under radiation, using discrete SiGe HBTs. The circuit tolerates high levels of gamma radiation, up to 12 MGy, features less than 2% drift in the forward current of the VCSEL and operates well above 10 MHz. The output duty cycle shows no notable degradation at 200 kHz, enabling the design of robust analog and digital communication systems using pulse-width-modulation (PWM) schemes. [ABSTRACT FROM AUTHOR]

Fiber Bragg gratings are all-fiber wavelength-selective refractive index structures manufactured through UV exposure of optical fibers. Their applications range from WDM all-fiber filters, dispersion compensators and fiber laser resonators for optical telecommunication applications to different types of point or distributed optical fiber sensors for a large variety of applications. The nuclear industry is considering the use of photonic technology for data communication in the next generation of nuclear power plants. In addition, fiber Bragg grating sensors are being evaluated by the nuclear industry for structural integrity and temperature monitoring. This work aims to study, in harsh radiation environments, a new type of FBG referred to as chemical composition grating. These gratings differ from other types of FBG in that their refractive index structure is attributed to a change in the chemical composition. Chemical composition gratings have shown to be extremely temperature stable surviving temperatures in excess of 1000 °C. We have experimentally studied the effect of very harsh gamma- neutron radiation on the properties of chemical composition gratings fabricated in a Ge-F doped silica optical fiber. [ABSTRACT FROM AUTHOR]

Presents a study that investigated dose-rate effects on gamma-irradiated fiber Bragg grating filters. Examination on the application problem concerning electronic or photonic equipment in nuclear environments; Analysis of fiber Bragg gratings under pure gamma radiation; Assessment on the use of fiber-optic technology for data communication in nuclear power plants.

Presents a study that investigated the radiation-induced absorption of pure silica core fibers exposed to fission nuclear radiation. Background on the effect of ionizing radiation on the optical properties of silicon dioxide glasses; Analysis of an estimate of the recoil proton contribution; Examination of hydrogen diffusion.

The fiber Bragg gratings (FBGs) inside photonic crystal fibers (PCFs) having high fiber birefringence, such as in PCF with butterfly shape microstructure, are characterized by two Bragg peaks. The spectral distance between these two peaks is not affected by a change of temperature or by a longitudinally applied strain, but this spectral separation evolves when the sensor is subjected to a transversal strain. This makes such FBGs inscribed in highly birefringent PCFs very interesting for structural health monitoring of civil structures, as well as for operation in harsh environments such as the ones associated with the nuclear industry. In this paper, we monitor the radiation-induced Bragg wavelength shift (RI-BWS) of the punctual sensor and the radiation-induced attenuation in the fiber used for its inscription up to a dose of 1.5 MGy(SiO2). Even if we observe a RI-BWS for both Bragg peaks, the spectral distance between them only slightly evolves, of less than 10 pm. These gratings are then very promising sensors for the structural health monitoring of nuclear facilities. [ABSTRACT FROM AUTHOR]

The effect of gamma-radiation on the spectral characteristics of FBGs has been studied experimentally. The FBGs were fabricated in optical fibers with a GeO2 concentration in the core in a range from several to 99 mol.%. Various pre- and post-fabrication treatments were applied with the aim to improve the radiation tolerance of the FBGs. The best result was obtained for a Type ha annealed grating written in SM310 fiber, where the Bragg peak shift saturated at a 12 pm level and an amplitude change of 0.04 dB with the maximal dose of about 50 kGy. [ABSTRACT FROM AUTHOR]

The radiation responses of two erbium doped fibers are studied in harsh pulsed X-ray and gamma ray environments. Their transient and continuous responses were measured in the near-infrared spectral range. The online transmission measurement of Radiation-Induced Attenuation (RIA) show no detectable change in the 1450-1600 nm erbium-ions-absorption domain, whereas the background losses from the silica-based host matrix are strongly increased by the creation of point defects. For both harsh environments, the rare-earth doped samples exhibit higher RIA levels compared than standard passive optical fibers. From all our measurements, we proposed that the main contribution to the induced losses is due to the radiation-induced changes of the host matrix rather than changes related to erbium ions. Photo-luminescence analyses confirm the generation of NBOHC in erbium doped fibers and suggest the existence of energy transfer between the radiation-induced point defects and the Er3+ ions. [ABSTRACT FROM AUTHOR]

We characterized the responses of three erbium-doped fibers with slightly different concentrations of rare-earth ions (240-290 ppm) and Al2O3 (7-10 wt.%) during proton and γ-ray exposures. We have simultaneously measured the radiation-induced attenuation (RIA) around the Er3+ ion pumping wavelength (980 nm) and the associated changes of the Er3+ emission around 1530 nm. The three erbium-doped fibers show similar radiation responses. All fibers exhibit RIA levels between 9 × 10-3 and 1.7 × 10-2 dB m-1 Gy-1 at 980 nm and between 4 × 10-3 and 1.1 × 10-2 dB m-1 Gy-1 at 1530 nm. Protons and -y-rays lead to similar radiation damages, with small differences between the protons of different energies (50 MeV and 105 MeV). Furthermore, we have performed online measurements of the spectral dependence of RIA from 600 to 1600 nm and offline measurements from 1200 to 2400 nm. The three fibers exhibit the same spectral response. Losses decrease monotonically from the visible to the infrared part of the spectrum. We have performed spectral decomposition of these RIA curves with the help of absorption bands previously associated with radiation-induced point defects. Our analysis shows that the main part of the RIA (600-1700 nm) in erbium-doped glass can be explained by the generation of Al-related point defects. The other defects related to the germanium and phosphorus doping of the silica seem to have a lower contribution to the induced losses. The Er3+ ion properties seem to be mainly unaffected by proton exposure, suggesting a solvation shell around the Er3+ ion formed by Al2O3 species. [ABSTRACT FROM AUTHOR]

The assessment of the durability of candidate space components and materials requires the use of ground laboratory testing facilities when no reliable information exists in the published literature. Accelerated tests simulating the radiation/temperature/vacuum environment need to be performed to investigate possible synergistic degradation effects. An irradiation chamber combining high vacuum and thermal cycling with a large range of gamma dose rates has been designed and constructed for this purpose at SCK·CEN, the Belgian Nuclear Research Center. The irradiation chamber module with actively-controlled vacuum is designed to fit in our gamma irradiation facilities. The vacuum irradiation module operates in the high-vacuum regime even in the presence of moderate outgassing from polymer materials. A pressure of 10-5 mbar can be routinely achieved but lower pressure can be obtained in the case of inert and mineral materials. In addition to the facility description, our paper discusses preliminary results of radiation-assisted outgassing of common polymers obtained using this new vacuum irradiation module. [ABSTRACT FROM AUTHOR]

Future maintenance tasks of the International Experimental Thermonuclear fusion Reactor (ITER) will require communication links between the remotely operated equipment in the reactor vessel and the control room, that are radiation tolerant up to MGy dose levels. We therefore assessed the DC behaviour of a COTS SiGe heterojunction bipolar transistor (HBT) under gamma radiation up to more than 4 MGy. The DC current gain (β) presents a limited loss of about 30% for a base current of 100 μA. Our in-situ measurements allowed us to adapt the manufacturer's SPICE model and account for these radiation effects. Circuit-hardened driving electronics for both photonic transmitters and receivers can hence be designed. [ABSTRACT FROM AUTHOR]

We have investigated the variation of the optical absorption induced by pulsed (dose rate > 108 rad/s) and continuous (<50 rad/s) γ-ray exposures in pure-silica-core optical fibers. Tested multimode waveguides, designed with well-defined concentrations of hydroxyl groups and chlorine impurity, are possible candidates for integration in the plasma diagnostics of LMJ and ITER facilities. We evaluated their radiation-tolerance to low dose levels (<5 × 104 rad) in the visible and near-infrared parts of the spectrum. We measure the time dependent changes (10-9–10-1 s) of the radiation-induced attenuation (RIA) at fixed wavelengths and we complete these measurements with a spectral (450–1100 nm) analysis of these losses in the time range from 10-2 to 10³ s. We compared the responses obtained under transient exposures with measurements done at same dose levels (5 × 10³ rad) with lower dose rate (<10² rad/s). We showed that the radiation-induced changes are strongly dose rate dependent for this kind of optical fibers. Depending on the hydroxyl group concentration in the silica-glass, different point defects are shown to alter the fiber transmission after both irradiation types. The self-trapped holes play a particular role in the transient responses of optical fibers whereas non-bridging oxygen hole centers are mainly responsible for γ-ray radiation-induced losses. The consequences of these different behaviors for the integration of optical fibers in the LMJ are discussed. [ABSTRACT FROM AUTHOR]

Raman Distributed Temperature Sensors (RDTS) are attractive for the monitoring of large structures in nuclear power plants such as containment structures and coolant loop systems. We demonstrate the high radiation tolerance of a Raman distributed fiber optic temperature sensor, up to total gamma doses in excess of 300 kGy, using a double-ended configuration and commercially-available optical fibers. [ABSTRACT FROM AUTHOR]

The radiation tolerance testing of materials or opto-electronic components in a nuclear reactor requires a careful determination of the different components of the mixed gamma-neutron field. While the characterization of the neutron field can be performed using, for example, activation foils and validated by Monte-Carlo computation codes, the experimental measurement of the in-reactor gamma dose rate requires the use of costly ionization chambers. In this paper, we evaluate the possibility of using Red Perspex from Hanvell Technologies for routine gamma dosimetry in mixed gamma neutron field. Self-powered gamma detectors and ionization chambers were used as reference dosimeters. We show that the accuracy of the Red 4034 dosimeter's is better than 10% in mixed gamma-neutron fields. [ABSTRACT FROM AUTHOR]

The radiation behavior of a commercially available Er-doped fiber is evaluated under varying gamma dose rates with in-situ spectral loss measurements. Complementary post-irradiation photoluminescence measurements allow us to better under- stand the radiation effects. Our results suggest that the microscopic enviromnent of the Er3+ ions is not much affected by the gamma irradiation, unlike the host matrix. We discuss the impact for potential applications of these commercially available fibers in radiation environments. [ABSTRACT FROM AUTHOR]

We evaluated the performances of the hydrogen-loading technique to reduce the radiation-induced absorption in optical fibers in the visible part of the spectrum. A reduction factor as large as one order of magnitude can be obtained in high dose-rate regime. Based on a spectral deconvolution method, we showed that hydrogen preferentially interacts with NBOHC defects while the number of POR defects is not affected. [ABSTRACT FROM AUTHOR]