An engineering and design activity in a project of developing International Thermonuclear Experimental Reactor is accumulating data on radiation effects in optical materials and components to be used for plasma diagnostics and for remote sensing. Radiation effects of neutrons, gamma-rays, and energetic-particles are quantitatively evaluated and a database is being made for designing optical components to be used in relatively heavy radiation environments.
Nine different fused silica core optical fibers were irradiated in a fission reactor up to an ionizing dose of 109Gy and a fast neutron fluence of 1023n/m2 at 400 K. One specimen, fluorine doped and specially sintered and annealed, showed good radiation resistance in the wavelength range of 300 - 1850 nm. Results showed that the fibers can be applied in a neutron associated heavy radiation environments.
Optical fiber technology is seriously considered for communication and monitoring applications during the operation and maintenance of future thermonuclear fusion reactors. Their environment is characterized, in particular, by possibly high gamma dose-rates and total doses up to 100 MGy. The feasibility of applying photonic technique in such intense radiation fields therefore needs to be assessed. Whereas many reports deal with the radiation behavior of a variety of fiber-optic devices, only little information is available on the radiation tolerance at high total dose (e.g. > 1 MGy). We describe our recent results obtained at fiber-optic components intended for ITER (International thermonuclear Experimental Reactor) remote-handling applications. We have conducted high total dose (up to 15 MGy) irradiation experiments on a variety of COTS fiber- optic devices, including edge-emitting laser diodes, vertical-cavity surface-emitting lasers, PIN photodiodes and single-mode optical fibers. A remarkably low radiation induced loss was obtained on a single-mode pure silica core optical fiber, whereas VCSELs confirmed their excellent radiation hardness. With the exception of photodiodes, the optical characteristics of selected fiber-optic devices seem to be able to cope with high total gamma doses. However, our results also indicate that radiation induced degradation of connector assemblies might limit their use in severe radiation environments.
Radiation resistant fused silica core optical fibers, 900 ppm OH doped with their hydrogen treated fibers with a plastic jacket, 18000 ppm OH doped one having very low optical transmission loss with a carbon jacket, and a fluorine doped fiber with a plastic jacket, were irradiated in a JMTR fission reactor, at 400 +/- 10 K with a fast neutron (E > 1 MeV) flux of 3.2 X 1017 n/cm2s and a gamma dose rate of 3 X 103 Gy/s for 527 hours. Their optical transmission loss at 850 nm was measured in- situ during irradiation.
Nuclear industry may benefit from the implementation of Optical Fiber Sensor (OFS) technology. This is obvious if the OFS integrates features that meet specific nuclear sensing needs, such as distributed dose monitoring in underground radioactive waste disposals. The use of radiation sensitive fibers for dosimetry has already been proposed in literature. In this paper, we report on our gamma irradiation of such dedicated Ge-P co-doped and pure P-doped optical fiber, fabricated by the Fiber Optic Research Center in Moscow. We show that after a careful selection of the wavelength at which the radiation-induced attenuation is measured, it is possible to reconstruct the dose within 20% accuracy by means of a linear model or a second order polynomial, depending on the temperature.
Optical fiber sensors (OFSs) offer numerous advantages, which include immunity to electromagnetic interference, intrinsic safety, small size, a possibly high sensitivity, multiplexing capabilities, and the possibility of remote interrogation. However, OFSs have a relatively low penetration in the commercial market, which is still dominated by standard electromechanical sensors. Nuclear environments are an example where particular OFSs might have a distinct superiority in the competition, but the feasibility of using OFSs in radiation environments still needs to be assessed. In the present paper we report on irradiation experiments performed to provide a sound basis for the design of a fiber Bragg grating based sensor capable to operate even under high total dose exposure.
The combined effects of radiation damage and accelerated ageing in COTS lasers and p-i-n photodiodes are presented. Large numbers of these devices will be employed in future High Energy Physics experiments and it is vital that these devices are confirmed to be sufficiently robust in terms of both radiation resistance and reliability. Forty 1310 nm InGaAsP edge-emitting lasers (20 irradiated) and 30 InGaAs p-i-n photodiodes (19 irradiated) were aged for 4000 hours at 80 degree(s)C with periodic measurements made of laser threshold and efficiency, in addition to p-i-n leakage current and photocurrent. There were no sudden failures and there was very little wearout-related degradation in either unirradiated or irradiated sample groups. The results suggest that the tested devices have a sufficiently long lifetime to operate for at least 10 years inside the Compact Muon Solenoid experiment despite being exposed to a harsh radiation environment.
During the past 30 years of development of Space optical instrumentation for such missions as METEOSAT, SPOT, HIPPARCOS and SILEX with ESA and CNES, Matra Marcon Space (MMS) has conducted extensive studies on the behavior of optical materials under irradiation such as quantifying transmission losses in optical glasses and measuring the dimensional stability of Zerodur as a substrate for mirror applications. Thanks to this background experience, MMS, in cooperation with SCK-CEN, is conducting a study (under ESA sponsorship) to define the approach for the gathering of a comprehensive data base to quantify these effects through the use of linear sensitivity coefficients (so-called `Dose Coefficients'). This follows recent investigations which have shown that the space radiation environment can affect not only transmission but also other characteristics of refractive optical materials in both classical and Cerium doped glasses. A number of selected examples from specific MMS studies will first be shown. Then, the actual approach being taken to this problem, on the basis of already obtained results from preliminary experiments performed by ESTEC, will be presented.
Future space systems will be based on components evolving from the development and refinement of new and existing photonic materials. Optically based sensors, inertial guidance, tracking systems, communications, diagnostics, imaging and high speed optical processing are but a few of the applications expected to widely utilize photonic materials. Knowledge of the response of these materials to space environment effects such as spacecraft charging, orbital debris, atomic oxygen, ultraviolet irradiation, temperature and ionizing radiation will be paramount to ensuring successful space applications. The intent of this paper is to address the latter two environments via a succinct comparison of the known sensitivities of selected photonic materials to the temperature and ionizing radiation conditions found in space and enhanced space radiation environments. Delineation of the known temperature and radiation induced responses in LiNbO3, AlGaN, AlGaAs, TeO2, Si:Ge, and several organic polymers are presented. Photonic materials are realizing rapid transition into applications for many proposed space components and systems including: optical interconnects, optical gyros, waveguides and spatial light modulators, light emitting diodes, lasers, optical fibers and fiber optic amplifiers. Changes to material parameters such as electrooptic coefficients, absorption coefficients, polarization, conductivity, coupling coefficients, diffraction efficiencies, and other pertinent material properties are examined for thermooptic and radiation induced effects. Conclusions and recommendations provide the reader with an understanding of the limitations or attributes of material choices for specific applications.
Cumulative effects on electro-optic devices are presented based on the test results of combined temperature, vacuum and total dose gamma irradiation. The survivability criteria were established in IEEE Standard 1156.4. Testing of a PIN diode and an infrared light emitting diode, under thermal vacuum conditions to a total dose of 2 Mrads, was undertaken.
Optical and infrared interferometry will open new vistas for astronomy over the next decade. Space based interferometers, operating unfettered by the Earth's atmosphere, will offer the greatest scientific payoff. They also present the greatest technological challenge: laser metrology systems must perform with sub-nanometer precision; mechanical vibrations must be controlled to nanometers requiring orders of magnitude disturbance rejection; a multitude of actuators and sensors must operate flawlessly and in concert. The Interferometry Technology program at NASA's Jet Propulsion Laboratory is addressing these challenges with a development program that plans to establish technology readiness for the Space Interferometry Mission by early in the year 2001.
This paper describes the development of compact, polarization insensitive mode-locked erbium-doped fiber lasers producing picosecond pulses for use as optical sampling sources in photonic analog to digital converters (ADCs). High-sampling rate and high resolution ADCs are required to convert the `naturally occurring' received analog signals to digital signals suitable for on-board data processing. The laser was constructed in a linear cavity, Fabry-Perot configuration with the saturable absorber at one end of the cavity and a chirped fiber Bragg grating at the other end. Theoretical modeling of the pulse formation within the laser cavity is presented and is in close agreement with the experimental data. The influence of radiation effects on erbium-doped fiber and fiber Bragg gratings is also investigated.
Relatively simple photonic devices like optoisolators have been shown to be surprisingly sensitive to the natural radiation environment of space. This paper will present space results from the Microelectronics and Photonics Testbed Experiment looking into the mechanisms responsible for this damage.
The MIRAS space instrument under development by the European Space Agency will be used to measure ocean salinity and soil moisture of the Earth by listening to the Earth radiation at 1.4 GHz. The instrument is a microwave radiometer based on aperture synthesis technology: 84 antennae, divided over 3 arms, collect data which is then correlated in a central processing unit to simulate a single large antenna. Radiation data is digitized at the antennae. An optical harness distributes clocking data to the antennae to synchronize the digitizing of the data, and transports the captured binary data to the processing unit. Data from four antennae is grouped, resulting in a speed of 559.8 Mbps (16/20 encoding) per fiber. The optical harness is built using RoCC (Robust Communication Controller), a serializer/de-serializer/phase-recovery chipset being developed by Siemens (Herentals) in DMILL (Durci Mixte Isolant Logico Lineaire) technology for radiation hardened communication. The presentation gives an overview of the complete optical harness: fiber, transmitter and receiver, and focuses on technology choices made to realize the RoCC chipset. The chipset also accommodates other speeds, and can e.g. be used to realize fiber channel or gigabit ethernet using two fibers. Architectural details are provided.
A transmission data link has been simulated using a high speed digital signal to modulate a 1300 nm laser diode. A Nd:YAG laser was used to simulate ionizing effects induced by transient particle irradiation on the laser diode by creating carriers only in the laser cavity. With this method, calibration of ionizing effects, error amplitude and influence of operational parameters of the link (frequency, amplitude of modulation...) have been studied. Heavy ions at different energies have been used to confirm transient effects, but the perturbation duration, too short compared with the Nd:YAG, have limited observation of the transient error due to ionizing effects. Permanent damages have been observed and their origin linked with the particle.
Radiation Imaging diagnostics invariably utilize gated micro-channel plate intensified components matted to solid state camera systems. Imaging is accomplished by conversion of radiation patterns to light which is viewed by optical sensors. This paper describes the effects of transient ionizing radiation directly impinging upon the solid state photo sensors which are typically used in the camera systems. These spurious radiation effects can cause degradation of the camera image. Gamma and neutron studies from earlier work are reviewed as well as electronic and electro-optic mitigation techniques to alleviate the problems of unwanted induced radiation artifacts in these photo sensors. Characterization of the true optical gating properties of the gated micro-channel plate operated in the nanosecond region (which aids image capture in pulse radiation scenarios) is described. X-Ray radiography imaging with large format gated intensified camera systems using high energy pulsed sources in the MeV region is also described.