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For a first-of-a-kind nuclear fusion reactor like ITER, remote maintainability of neutron-activated and contaminated components is one of the key aspects of plant design and operations, hence a fundamental ingredient of its success, as well as of the demonstration of long-term viability of fusion as an energy source. The whole ITER Remote Maintenance System (IRMS) is of unprecedented complexity and includes specifically developed technologies. Its procurement and start of operation will represent a major innovation to maintenance in hostile environments. Europe is a key contributor, with three remote handling (RH) systems, a.k.a. packages, plus a robotic inspection and metrology tool, currently under design. This paper gives an update on the status of design and procurement activities related to the IRMS. It will first introduce some key aspects of the reactor remote maintainability, and then give an overview of the present configuration of the global system. After this, the scope, status and challenges of the European (EU) packages will be illustrated in more detail, together with some key technological developments. Finally, the way all these efforts are coordinated will be presented together with the overall implementation scenario and milestones, and the way they fit with ITER construction and operation.

In this work we present a study on teh Super Luminescent LIght Emitting Diodes (SLEDs) performance under high doses of gamma radiation. We investigate GaAs SLEDs with emission wavelengths around 830 nm. The devices were exposed to ionising radiation at a dose rate of about 4.7 Gy/s, up to a cumulated dose of 10.1 MGy in the CMF facility of the Belgian nuclear research centre SCK•CEN. We measured the device characteristics before adn after irradiation. We show that the SLED performance is only marginally affected.

International audience; In the framework of the fusion for energy radiation hard imaging system project, the main radiation effects affecting the image quality of a miniaturized complementary metal-oxide-semiconductor-based camera exposed to radiation doses up to 1 MGy(SiO 2 ) are investigated for ITER applications. The radiation effects related to two of the three subcomponents of the camera are investigated: the optical system (OS) and the illumination system (IS). Subsystem demonstrators have been manufactured selecting radiation tolerant or hardened materials and components to demonstrate the feasibility to withstand such high dose levels while fulfilling the ITER remote handling needs in terms of optical performances and miniaturization. Regarding the OS, the observed degradation of the radiation-hardened optical glasses used for the OS lenses is characterized in terms of both radiation-induced attenuation and radiation-induced refractive-index change. At the system level, impact of these phenomena on the OS demonstrator performances is discussed in terms of image contrast. Radiation test results highlight the high radiation tolerance of manufactured monochrome and color OS to both degradation mechanisms. Regarding the IS, the selected architecture consists in a ring of 20 commercially available light-emitting diodes (LEDs) with monochrome (amber) or white emissions. An appropriate choice for the LEDs allows designing an IS with the requested performances and slight degradation of its output power at the MGy dose levels. From the obtained results, developing miniaturized IS and OS subcomponents for MGy dose operation levels appears realistic using commercially available technologies and appropriate hardening procedures.

The ITER Neutral Beam cell will include a suite of Remote Handling equipment for maintenance tasks. This paper summarises the current status and recent developments in the design of the ITER Neutral Beam Remote Handling System. Its concept design was successfully completed in July 2012 by CCFE in the frame of a grant agreement with F4E, in collaboration with the ITER Organisation, including major systems like monorail crane, Beam Line Transporter, beam source equipment, upper port and neutron shield equipment and associated tooling. Research and development activities are now underway on the monorail crane radiation hardened on-board control system and first of a kind remote pipe and lip seal maintenance tooling for the beam line vessel, reported in this paper.

For a first-of-a-kind nuclear fusion reactor like ITER, remote maintainability of neutron-activated components is one of the key aspects of plant design and operations, and a fundamental ingredient for the demonstration of long-term viability of fusion as energy source. The European Domestic Agency (EU DA, i.e. Fusion for Energy, F4E) is providing important support to the ITER Organisation (IO) in specifying the functional requirements of the Remote Handling (RH) Procurement Packages (i.e. the subsystems allocated to EU DA belonging to the overall ITER Remote Maintenance Systems IRMS), and in performing design and R&D activities – with the support of national laboratories and industries – in order to define a sound concept for these packages. Furthermore, domestic industries are being involved in the subsequent detailed design, validation, manufacturing and installation activities, in order to actually fulfil our procurement-in-kind obligations. After an introduction to ITER Remote Maintenance, this paper will present status and next stages for the RH systems allocated to EU DA, and will also illustrate complementary aspects related to cross cutting technologies like radiation tolerant components and RH control systems. Finally, the way all these efforts are coordinated will be presented together with the overall implementation scenario and key milestones.

The ITER neutral beam cell will contain up to three heating neutral beams and one diagnostic neutral beam, and four upper ports. Though manual maintenance work is envisaged within the cell, when containment is breached, or the radiological protection is removed the maintenance must be conducted remotely. This maintenance constitutes the removal and replacement of line replaceable units, and their transport to and from a cask docked to the cell. A design of the remote handling system has been prepared to concept level which this paper describes including the development of a beam line transporter, beam source remote handling equipment, upper port remote handling equipment and equipment for the maintenance of the neutral shield. This equipment has been developed complete the planned maintenance tasks for the components of the neutral beam cell and to have inherent flexibility to enable as yet unforeseen tasks and recovery operations to be performed., Comment: 4 pages, 9 figures

International audience; In this review paper, we present radiation effects on silica-based optical fibers. We first describe the mechanisms inducing microscopic and macroscopic changes under irradiation: radiation-induced attenuation, radiation-induced emission and compaction. We then discuss the influence of various parameters related to the optical fiber, to the harsh environments and to the fiber-based applications on the amplitudes and kinetics of these changes. Then, we focus on advances obtained over the last years. We summarize the main results regarding the fiber vulnerability and hardening to radiative constraints associated with several facilities such as Megajoule class lasers, ITER, LHC, nuclear power plants or with space applications. Based on the experience gained during these projects, we suggest some of the challenges that will have to be overcome in the near future to allow a deeper integration of fibers and fiber-based sensors in radiative environments.

The gamma radiation-induced variation of the transconductance in the subthreshold region is studied for different back-gate voltages and for different kinds of SOI MuGFETs: devices with and without selective epitaxial growth (SEG) and 45° rotated transistors. Wide fin devices show a larger degradation when the back-gate is grounded. The back-channel of narrow fin transistors, on the other hand, needs to be inverted before degradation in the transconductance is observed. The radiation behavior of the transconductance is similar for devices with and without SEG. It is shown that the maximum variation in transconductance correlates with the mobility for narrow fin devices. This mobility varies when the transistor is rotated. For wide fin devices this correlation is not as strong.

The effect of an airgap deep trench isolation on the gamma radiation behavior of a 0.13 mum SiGe NPN HBT technology is studied with the help of in-situ measurements. The incorporation of this deep trench isolation in the technology leads to a lower degradation of the transistor during irradiation as well in forward-mode as in reverse-mode operation. A possible explanation is briefly mentioned.

This paper describes the characterization and SPICE model adaptations for a SiGe Heterojunction Bipolar Transistor (HBT) with a characteristic emitter width of 0.4 mum, which is part of the device library in a commercial 0.35 mum SiGe BiCMOS technology. The developed model is used to design and validate the operation of an integrated driver for a 1550 nm Vertical Cavity Surface-Emitting Laser (VCSEL). The static measurements of the driver during irradiation up to 600 kGy correspond well with the simulations. A second irradiation experiment up to 1.6 MGy allowed us to verify the dynamic operation. Investigation of the eye diagram of the output signal both before and after irradiation revealed no significant signal degradation.

International audience; We compare the visible and infrared luminescence spectra obtained by a green (514.5 nm) and infrared (830 nm) excitation of an erbium-doped fiber before and after irradiation with 105 MeV protons to an equivalent dose of 0.6 kGy(Si). For the irradiated fiber, we measured an increase of the luminescence intensity in this wavelength range due to the generation of additional color centers. Radiation defects such as Ge-NBOHC, Si-NBOHC are generated in both the fiber core and the cladding by the 105 MeV protons. They contribute through their luminescence bands at 1.84 eV (FWHM = 0 2 eV) and 2 eV (0.2 eV) to the fiber emission spectra. Two other pre-existing luminescence bands at 1.75 eV (0.32 eV) and 2.1 eV (0.37 eV), associated to host-matrix-point-defects, are enhanced by proton-irradiation. The Er3+ ions luminescence in both visible and infrared spectral ranges is also affected by the irradiation.

International audience; Abstract—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 measurements 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

The proton irradiation effects on n-MuGFET devices with three different geometries (single fin, wide fin and multiple fin) are studied. Also, the effect of tensile strain in the fin on the radiation behavior is investigated. A fundamental difference in the radiation behavior between the non-strained and the strained devices is found. The degradation of the strained devices is most affected by the mobility decrease of the backside transistor. The non-strained devices show a much lesser back gate mobility degradation. For these devices the creation of positive oxide traps is dominant. This shifts the onset of the back channel to lower gate voltages, inducing a transconductance increase at intermediate gate voltages. This effect is less pronounced for single fin MuGFETs. At higher gate voltage, the transconductance decreases for the strained and increases for the non-strained transistors.

International audience; Abstract—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 gamma-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 gamma-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.

The radiation hard design of a 155 Mb/s, 0.7 mum CMOS driver for a vertical-cavity surface-emitting laser (VCSEL) is presented. The circuit features enhanced tolerance to radiation induced shifts in the device characteristics by employing a replica-based feedback mechanism. The layout was achieved using an in-house developed radiation hardened component library. At a low dose rate of 4.5 Gy/h or 450 rad/h, the output current remains constant up to at least 3.5 kGy. At a dose rate of 21 kGy/h, the output current of the driver drops by 10% at a dose of 3.5 MGy and breaks down completely at 5.5 MGy.

Several single mode silica-based fibers with different levels of erbium concentrations have been tested under Co-60 gamma radiation. Irradiation has been performed at a dose-rate of similar to 30 Gy/h to a total dose of similar to 2 kGy. Transmission spectra were measured in situ in a spectral range from 1250 to 1630 nm. The measurements show no detectable change in the Er-ions luminescence and absorption spectrum profiles, while a significant (similar to dB/m/kGy at 1530 nm) increase in transmission losses is attributed to the silica host matrix modifications. This conclusion is drawn based on the post-irradiation photo-luminescence analyzes realized with a confocal micro-spectrometer (514.5 nm excitation, P similar to 2 mW). (c) 2007 Elsevier B.V. All rights reserved.

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 (beta) presents a limited loss of about 30% for a base current of 100 muA. 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.

A digital VCSEL driver has been designed, simulated and assessed under radiation, using discrete SiGe HBT's. 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.

One of the key maintenance operations for the ITER tokamak is the remote replacement of its divertor system. The components making up this system are expected to be activated to a level of several hundred gyrations per hour and contaminated with hazardous and/or activated dust (beryllium, carbon, tungsten) and tritium. A suite of specialized remote handling (RH) equipment is, therefore, necessary to facilitate divertor exchange. This paper describes the ITER divertor maintenance approach together with recent European efforts towards the design and development of the associated remote handling equipment and procedures.

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 understand the radiation effects. Our results suggest that the microscopic environment of the Er/sup 3+/ 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.

A first assessment of the total dose behavior of bulk p-multiple-gate field-effect transistors (MuGFETs) is reported, and special attention is given to the effect of the fin width on the radiation behavior. It was found that the effect of radiation-induced traps in the shallow trench isolation is larger when the fin width decreases. This is in contrast to the total dose behavior of SOI MuGFETs.

The basic components of fiberoptic links, such as light emitting diodes (LED), pin-type photodetectors (PD) and optical fibers are evaluated under (/sup 60/Co) /spl gamma/-ray irradiation, so as to ascertain their qualification for nuclear applications and to develop predictive models for their behavior under well defined environmental conditions, such as those encountered in nuclear power plants. This paper presents some results of irradiation tests, together with a discussion of proposals for optical fibers' behavioral models.

The maintenance requirements for the equipment in the ITER Neutral Beam Cell requires components to be lifted and transported within the cell by remote means. To meet this requirement, the provision of an overhead crane with remote handling capabilities has been initiated. The layout of the cell has driven the design to consist of a monorail crane that travels on a branched monorail track attached to the cell ceiling. This paper describes the principle design constraints and how the remote handling attributes were applied to the concept design of the monorail crane, concentrating on areas where novel design solutions have been required and on the remote recovery requirements and solutions., 4 pages, 10 figures

In the present article the integration of the convective diffusion equation for compression at a constant dilatation rate is presented, which enables us to describe the course of surface tension with time for the desorption rate of an adsorbed monolayer. The theory is evaluated by compression experiments performed with decanoic acid and Triton X-45.

Recent developments of stability control in mines, essentially based on Ge-doped fiber Bragg gratings (FBG) are reported including results about the different aspects of the system: accurate characterizations of FBG, sensor network topology and multiplexing method, user interface design and sensor packaging. >

The pressure versus area curves for a spread myristic acid monolayer are markedly affected by the compression velocities as becomes clear from the published results of K. Motomura, A. Shibata, M. Nakamura, and R. Matuura ( J. Colloid Interface Sci. 29, 623, 1969). This is due to the dissolution of spread molecules into the bulk solution. From these apparent Π- A curves the thermodynamic Π- A curve (without a phase transition), where no diffusion is present, can be constructed in three different ways. A qualitative explanation for the different diffusion relaxation times obtained by each approach is given.

This paper presents the design of a radiation tolerant configurable discrete time CMOS signal conditioning circuit for use with resistive sensors like strain gauge pressure sensors. The circuit is intended to be used for remote handling in harsh environments in the International Thermonuclear Experimental fusion Reactor (ITER). The design features a 5 V differential preamplifier using a Correlated Double Sampling (CDS) architecture at a sample rate of 20 kHz and a 24 V discrete time post amplifier. The gain is digitally controllable between 27 and 400 in the preamplifier and between 1 and 8 in the post amplifier. The nominal input referred noise voltage is only 8.5 μV while consuming only 1 mW. The circuit has a simulated radiation tolerance of more than 1 MGy.

Experiments are presented to verify our theory (J. Colloid Interface Sci., 155, 271 (1993) concerning the steady state dynamic surface tension of a compressed adsorbed soluble monolayer with a constant dilatation rate. Two kinds of experiments were performed: (i) expanding and compressing the surface with a constant dilatation rate (area changes logarithmically), while measuring the surface tension as a function of time, and (ii) expanding and compressing the surface respectively by a receding and an advancing meniscus in a capillary, while measuring the pressure as a function of time. It is shown that good agreement between the performed experiments and the theory is obtained.

In this work the influence of Selective Epitaxial Growth (SEG), high- k gate-dielectric and rotation of the channel on the low frequency (LF)-noise is investigated. The carrier number fluctuations dominate the 1/ f noise for all the devices studied. An unusual effective trap density profile is found. It decays with a larger distance from the interface. This implies a higher trap density in the interfacial SiO 2 -layer, compared with the high- k dielectric. The shape of the profile is different for a HfSiON gate-dielectric compared with a HfO 2 gate-dielectric. Higher trap densities are found for the latter. The Selective Epitaxial Growth (SEG) and channel orientation show only a negligible impact on the noise behavior when a HfSiON-dielectric is used.

Near UV-visible absorption coefficients of an erbium-doped optical fiber were investigated through an original technique based on a transverse cw UV-laser irradiation operating at 244 nm. Such irradiation leads to the generation of a quite intense guided luminescence signal in near UV spectral range. This photoluminescence probe source combined with a longitudinal translation of the fiber sample (at a constant velocity) along the UV-Iaser irradiation, presents several major advantages: (i) we bypass and avoid the procedures classically used to study the radiation induced attenuation which are not adapted to our case mainly because the samples present a very strong absorption with significant difficulties due to the injection of adequate UV-light levels in a small fiber diameter: (ii) the influence of the laser irradiation on the host matrix of the optical fiber is directly correlated to the evolution of the generated photoluminescence signal and (iii) in our experimental conditions, short fiber sample lengths(typically 20-30 cm) suffice to determine the associated absorption coefficients over the entire studied spectral domain. The generated photoluminescence signal is also used to characterize the absorption of the erbium ions in the same wavelength range with no cut-back method needed. (C) 2008 Elsevier B.V. All rights reserved.

This paper describes the characterization and SPICE model adaptations for a SiGe Heterojunction Bipolar Transistor (HBT) with a characteristic emitter width of 0.4μm, which is part of the device library in a commercial 0.35μm SiGe BiCMOS technology. The developed model is used to design and validate the operation of an integrated driver for a 1550nm Vertical Cavity Surface-Emitting Laser (VCSEL). The static measurements of the driver during irradiation up to 600 kGy correspond well with the simulations. A second irradiation experiment up to 1.6 MGy allowed us to verify the dynamic operation. Investigation of the eye diagram of the output signal both before and after irradiation revealed no significant signal degradation.

We evaluated the radiation tolerance of volume holographic elements written in photo-thermo refractive glass. To do so these elements were exposed to Co-60 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.

We compare the visible and infra-red luminescence spectra obtained by a green (514.5 nm) and infra-red (830 nm) excitation of an erbium-doped fiber before and after irradiation with 105 MeV protons to an equivalent dose of 0.6 kGy(Si). For the irradiated fiber, we measured an increase of the luminescence intensity in this wavelength range due to the generation of additional color centers. Radiation defects such as Ge-NBOHC, Si-NBOHC are generated in both the fiber core and the cladding by the 105 MeV protons. They contribute through their luminescence bands at 1.84 eV (FWHM=0.2 eV) and 2 eV (0.2 eV) to the fiber emission spectra. Two other pre-existing luminescence bands at 1.75 eV (0.32 eV) and 2.1 eV (0.37 eV), associated to host-matrix-point-defects, are enhanced by proton-irradiation. The Er3+ ions luminescence in both visible and infra-red spectral ranges is also affected by the irradiation.

The effect of airgap deep trench isolation on the radiation behavior of a 0.13 mum NPN SiGe:C HBT is studied and compared with standard components with conventional junction isolation. Proton and gamma irradiations are performed. The only effect discerned on this technology after a proton irradiation of 7 kGy is a decrease in collector current at higher base-emitter voltages. After 100 kGy gamma irradiation, no change in collector current is observed. However, the base current increases severely at lower base-emitter voltages. In forward-mode the base current degradation of devices featuring deep trench isolation is higher compared to conventional devices. In reverse-mode the effect is opposite: degradation is higher for conventional devices. The difference in degradation between the two isolation types is smaller in forward-mode operation.

We discuss on-going reliability studies of micro-optical components and assemblies as conducted in the EU FP6 Network of Excellence on Micro-Optics "NEMO". We focus on three case studies including first biaxial fatigue testing of micro-optical components, second reliability testing and quality control of MEMS and third micro-interferometric tomography for measuring optical fibre refractive index changes. For each of these case studies we discuss the dedicated measurement and characterization methods as well as first results and the perspectives for future research.

This paper presents the first results of long term experiments conducted within the SOFTI (Study of Optical Fibres and components under Thermal ageing and Irradiation) project. This on-going 6-years study is intended to determine the effects of ageing on the behaviour of optical fibres and their fibre-end components submitted to harsh environments, with respect to the safety of nuclear facilities. The test program consists of irradiations at low dose rates with different thermal constraints and spool radius. After completion, these tests will enable us to write a guideline for qualification procedures related to future fibre-optic systems, for their applications in nuclear facilities. The observations of these first results show a clear dependence of the radius of curvature for the radiation induced loss. To our knowledge, it is the first time that this was experimentally verified for a radius of curvature superior to 6 cm.

The deployment of optical fibre networks for communication and monitoring in nuclear environments, including nuclear power plants, future thermonuclear power reactor buildings and even spacecrafts is a very particular issue. A major reliability problem when dealing with photonics in these environments is the presence of nuclear radiation fields. It is well known that electronic or photonic components may suffer from exposure to high-energy radiation. Any resulting system malfunctions might have dramatic consequences on safety and cost and it is therefore essential to investigate the reliability of optical communication devices exposed to radiation. In this paper, we try to summarize the degradation mechanisms of state-of-the-art fibre optic components. We illustrate these findings with recent results obtained on commercially available optical fibre components.

The future International Thermonuclear Experimental Reactor (ITER) requires remote handling tools for its maintenance that will operate in a harsh environment. The numerous instrumentation cables for this maintenance equipment call for (de)multiplexing solutions, in order to reduce the umbilical size. Fibre-optic data links, using commercial-off-the-shelf (COTS) components, are seriously considered as a radiation tolerant solution, offering wavelength encoded multiplexing possibilities. However, an adapted modus operandi for a reliable assessment of this evolving technology is needed, to enable their long-term implementation in a radiation environment. In this paper, we present a methodology towards qualification methods for these instrumentation data links, and illustrate it with results obtained for different individual components. These results should enable the future design of robust architectures for communication links.

We design and test a radiation tolerant opto-electronic transmitter based on vertical-cavity surface-emitting lasers (VCSELs) and dedicated driver electronics consisting of discrete components. VCSELs have already demonstrated their good radiation tolerance level. We confirm this by on-line irradiation experiments on such devices up to a 10 MGy total dose. For the design of the driver circuit, we rely on discrete commercial-off-the-shelf (COTS) bipolar transistors. When the radiation induced degradation of these components is considered within the design of the circuits, total dose levels larger than 1 MGy can be tolerated. The driver uses standard TTL input signals and delivers a forward current of 12 mA to a pigtailed 840 nm VCSEL. SPICE simulations show that the driver still delivers a sufficient forward current to the VCSEL, in spite of the radiation induced degradation of the h/sub fe/ and V/sub CEsat/ values of the transistors. These simulations are verified by our experiments. At a total dose of 1 MGy, the measured decrease of the forward current is only about 8 %, as measured for three driver circuits This induces an optical output power decrease that can still be tolerated with irradiated VCSELs, as shown by our experiments. We conclude that a high total dose hardened optical transmitter for use in nuclear instrumentation systems can be fabricated using discrete COTS bipolar transistors, COTS vertical-cavity surface-emitting lasers and COTS optical fiber.