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New diagnostic measurements have driven important steps forward in the JET experimental program in areas related to H-mode, advanced tokamak physics, and divertor erosion-redeposition phenomena. As a consequence, a program of diagnostics developments has been started. The first part of the article describes recent diagnostic measurements, with special emphasis on the motional stark effect observation of the currentless core, the poloidal velocity measurements by charge exchange recombination spectroscopy, the edge profile measurements with light detecting and ranging Thomson scattering and Li-beam emission, the real-time control of the q profile, and the first results from the quartz microbalance on divertor carbon deposition. The second part describes the program of diagnostics developments on JET that is being prepared for commissioning in 2004. Special emphasis will be devoted to the new high-resolution Thomson scattering, the Li-beam polarimetry system (still under assessment), ITER-relevant activity, like the mirror test program (as a support activity for the ITER diagnostics), and the effort on fusion products diagnostics: neutron spectroscopy and lost alpha collectors.

In this paper we investigate the use of lines from tungsten (W) ions to measure the properties of W impurities in ITER plasmas. We calculate the intensities of the brightest spectral lines expected to be radiated by W ions with wavelengths longer than 45 A, abundance of 10−4 and at densities of 1020 m3. Using the calculated wavelengths and intensities we propose a concept for segmented multilayer‐coated imaging telescopes that could be used to investigate the properties of W impurities as a function of time and space using spectral lines from highly ionized W

In Tokamaks, the Electron Cyclotron Emission (ECE) radiation frequency spans from 80 GHz up to 1 THz for high magnetic field (Bt>5 T) and higher harmonics (n>2). This frequency ranges between Microwaves and Far Infrared (FIR), moulding an intrinsically hybrid nature for ECE diagnostics(1). Signal detection is carried out in two surprisingly different ways: electronics and optics. The two detection methods, beyond the chief external differences, are conceptually the same. The dualism often reflects the mindset of the laboratory performing the measurement. In this paper we discuss a different approach to an integrated instrument. A traditional quasi‐optical interferometer is the first down‐conversion stage with intrinsic broad band capability. Its output signal can then be analysed with a radio‐style detection, in the amenable kHz frequency range.

This year marks the 30th anniversary of the decision on 17 October 1977 by the European Council of Ministers to proceed with the JET project. Very little thought had been given to the diagnostic requirements during the design phase—indeed many people assumed that JET would not do detailed physics studies and would need only a few basic diagnostics. Of course this view turned out to be incorrect—JET needed a comprehensive set of diagnostics and has conducted a very extensive physics programme. The large physical dimensions of JET, the radiation environment and the stringent interface standards radically changed our concept of diagnostics compared to the smaller fusion experiments that had gone before. In this paper I will review some of the experience on burning plasma diagnostics on JET.

To investigate the deuteron and triton density ratio in core plasmas, a new methodology with measurement of tritium (DT) and deuterium (DD) neutron count rate ratio using a double‐crystal time‐of‐flight (TOF) spectrometer is proposed. Multi‐discriminator electronic circuits for the first and second detectors are used in addition to the TOF technique. The optimum arrangement of the detectors and discrimination window were examined considering the relations between the geometrical arrangement and deposited energy using a Monte Carlo Code, PHITS (Particle and Heavy Ion Transport Code System). An experiment to verify the calculations was performed using DD neutrons from an accelerator.

A probing He0 beam for confined alpha particle measurement using a double charge exchange process is now under development. A proof of principle experiment for ground‐state He0 beam production will be performed on a test stand. Several methods are developed to measure the metastable fraction of a He0 beam. A full‐size strong‐focusing He+ source has been constructed and sufficient beam current was achieved with a beam size tolerable to be used on ITER.

The advanced tokamak research program at DIII‐D relies critically on the measurement of the current density profile. This was made possible by the development of a Motional Stark Effect (MSE) polarimeter that was first installed in 1992. Three major upgrades have since occurred, and improvements in our understanding of critical performance issues and calibration techniques are ongoing. In parallel with these improvements, we have drawn on our DIII‐D experience to begin studies and design work for MSE on burning plasmas and ITER. This paper first reviews how Motional Stark Effect polarimetry (MSE) is used to determine the tokamak current profile. It uses the DIII‐D MSE system as an example, and shows results from the latest upgrade that incorporates an array of channels from a new counter‐Ip injected neutral beam. The various calibration techniques presently used are reviewed. High‐leverage or unresolved issues affecting MSE performance and reliability in ITER are discussed. Next, we show a four‐mirror collection optics design for the two ITER MSE views. Finally, we discuss measurements of the polarization properties of a few candidate mirrors for the ITER MSE. Work supported by the U.S. Department of Energy under W‐7405‐ENG‐48.

The roles of fusion products in diagnosing plasmas are quite diversified and rich in scientific content. From the early days to the new frontier of burning plasmas, the study of fusion products has allowed a deeper understanding of the physics found in these plasmas, spanning all configurations, in both magnetic and inertial confinement. In many early experiments, the measurement of plasma performance was based almost entirely on neutron yield measurements. Since then, the capability to measure fusion products has grown tremendously, and many new measuring techniques have been successfully tested and used in experiments. The first role is based on single‐particle diagnosis, which can yield important information on performance, confinement, source and current profiles, plasma fluctuations, effects of ripples, MHD mode structure, etc. The second role, which has expanded tremendously in the last few years, includes the diagnosis of collective effects, which can yield additional information on instabilities, ...

Due to high neutron and gamma‐ray yields and large size plasmas many future fusion reactor plasma parameters such as fusion power, fusion power density, ion temperature, fuel mixture, fast ion energy and spatial distributions can be well measured by various fusion product diagnostics. Neutron diagnostics provide information on fusion reaction rate, which indicates how close is the plasma to the ultimate goal of nuclear fusion and fusion power distribution in the plasma core, which is crucial for optimization of plasma breakeven and burn. Depending on the plasma conditions neutron and gamma‐ray diagnostics can provide important information, namely about dynamics of fast ion energy and spatial distributions during neutral beam injection, ion cyclotron heating and generated by fast ions MHD instabilities. The influence of the fast particle population on the 2‐D neutron source profile was clearly demonstrated in JET experiments. 2‐D neutron and gamma‐ray source measurements could be important for driven plasma heating profile optimization in fusion reactors. To meat the measurement requirements in ITER the planned set of neutron and gamma ray diagnostics includes radial and vertical neutron and gamma cameras, neutron flux monitors, neutron activation systems and neutron spectrometers. The necessity of using massive radiation shielding strongly influences the diagnostic designs in fusion reactor, determines angular fields of view of neutron and gamma‐ray cameras and spectrometers and gives rise to unavoidable difficulties in the absolute calibration. The development, testing in existing tokomaks and a possible engineering integration of neuron and gamma‐ray diagnostic systems into ITER are presented.

Neutron emission profiles are routinely measured in JT‐60U Tokamak. Stinbene neuron detectors (SNDs), which combine a Stilbene organic crystal scintillation detector (Stilbene detector) with an analog neutron‐gamma pulse shape discrimination (PSD) circuit, have been used to measure neutron flux efficiently. Although the SND has many advantages as a neutron detector, the maximum count rate is limited up to ∼1× 105 counts/s due to the dead time of the analog PSD circuit. To overcome this issue, a digital signal processing (DSP) system using a Flash‐ADC has been developed. In this system, anode signals from the photomultiplier of the Stilbene detector are fed to the Flash ADC and digitized. Then, the PSD between neutrons and gamma–rays are performed using software. The photomultiplier tube is also modified to suppress and correct gain fluctuation of the photomultiplier. The DSP system has been installed in the center channel of the vertical neutron collimator system in JT‐60U and applied to measurements of n...

Experiments on plasma configurations with Liquid Lithium Limiter (LLL) have been performed on FTU to investigate liquid lithium facing the plasma. The liquid lithium surface with capillary porous system (CPS) has been inserted in the scrape off layer (SOL) of the FTU vacuum chamber in various plasma discharges. MHD activity in discharges with and without LLL has been investigated and compared. The main MHD effect observed with LLL is a reduction of the amplitude of tearing modes with poloidal (toroidal) number m = 2 (n = l). The magnetic activities in FTU are analysed by means of a set of poloidal field pick‐up coils. A total of 57 coils are installed at various toroidal and poloidal positions. In this paper we will describe in details the diagnostic apparatus and experimental results.

In the recent years Plasma Control has always increased his importance in any advanced experiment. It is now clear that ITER will not be able to operate without a quite advanced and sophisticated control apparatus. Necessarily this system will have to integrate several different aspects of the Plasma behavior. One of the most important parts of a closed loop control system is the quality of the measurement of the plasma parameters that should be controlled. Eventually, this aspect involves sophisticated and complex diagnostic apparatus. This paper presents an overview of the present status, and further studies and developments needed, in the next future, for the design and realization of an integrated plasma control system aimed at both stabilizing the plasma non-axisymmetric instabilities and controlling the most important internal plasma parameters. In particular the Edge Localized Modes (ELMs), the Neo-Classical Tearing Modes (NTM), the Resistive Wall Mode (RWM) and the Plasma Profiles control system necessities will be shortly illustrated. Keywords: Plasma, Control, Diagnostics PACS: 52.55.Fa, 52.70.Ds, 07.05.Dz.

Electron cyclotron resonance heating (ECRH) and current drive (ECCD), disruptive instability events and sawtooth activity have been demonstrated to produce suprathermal electrons in fusion devices. The importance of these phenomena for fusion reactors renders suprathermal electron generation and dynamics a key topic in the physics of burning plasmas. Here some significant results from the TCV tokamak are briefly reviewed and a preliminary design of a novel tomographic hard X-ray spectrometer proposed for TCV is discussed. The design is aided by simulations of tomographic reconstruction.

The code SPECE has been developed for the analysis of electron cyclotron emission (ECE) in a general tokamak equilibrium. The code solves the radiation transport equation along the ray trajectories in a tokamak plasma, in which magnetic equilibrium and plasma profiles are given either analytically or numerically, for a Maxwellian plasma or a non thermal plasma characterized by a distribution function that is the sum of drifting Maxwellian distributions. Ray trajectories are computed making use of the cold dispersion relation, while the absorption and emission coefficients are obtained solving the relevant fully relativistic dispersion relation valid at high electron temperature. The actual antenna pattern is simulated by means of a multi‐rays calculation, and the spatial resolution of the ECE measurements is computed by means of an algorithm that takes properly into account the emission along each ray of the beam. Wall effects are introduced in the code by means of a heuristic model. Results of ECE simulations in a standard ITER scenario are presented.

We give here a short overview of the status of the development for ITER thermography as performed by the CEA‐Cadarache and some of its collaboration partners. The topics that have been included in this synthesis are the status of the optical design, the role of multi‐wavelength mesurements, multicolour pyroreflectometry, photothermal methods, and reflection simulations and measurements.

This tutorial gives a brief introduction into passive spectroscopy and describes the working principles of bolometers, a high‐resolution grating spectrometer, and a novel X‐ray imaging crystal spectrometer, which is also of particular interest for profile measurements of the ion temperature and plasma rotation velocity on ITER and future burning plasma experiments.

Laser‐aided plasma diagnostics, aiming for establishment of reliable density measurement in next step magnetically confined fusion devices, are under development at the National Institute for Fusion Science. A new type of two color laser (57.2/47.6‐μm CH3OD) interferometer has been developed and its original function, vibration subtraction, was confirmed in a test stand. The line integrated density measurements by the polarimeter were demonstrated at Compact Helical System by the Cotton‐Mouton polarimeter and at the LHD by the Faraday rotation polarimater.

This paper offers a preliminary review of the present diagnostics and data analysis techniques in the domain of Soft X‐ray (SXR) emissions of fusion magnetic plasmas, including a short description of the theoretical background as well. Particular attention is devoted to the wide use of SXR tomography and impurity transport simulation. In their actual form, these techniques are not adequate to future real time applications. For this goal a step forward in the diagnosing and analysis of SXR emissions is required. The following part of the paper is therefore dedicated to the discussion of these improvements. The first one is the SXR tomography optimized for real time applications, like that one developed at Tore Supra (Cadarache, France). Fast 2‐D tomographic inversions using different techniques (regularisation of Minimum Fisher, Maximum entropy, Zernicke polynomial expansions), will be optimized to be performed in a few millisecond time scale, crucial for MHD analysis, mode detection and localisation. The ...

The present status of investigations on the first mirror (FM) problem is discussed on the basis of the last experimental results obtained in modern tokamaks and laboratory devices. Engineering solutions that are necessary for protection of Fms for CXRS and H‐alpha diagnostics are considered. Future plans for R&D that has yet to be done are presented. Results of neutron irradiation and heating tests of multilayered dielectric mirrors are given briefly.

For continuous operation expected in DEMO, all the plasma current must be non‐inductively driven, with self‐generated neoclassical bootstrap current being maximized. The control of such steady state high performance tokamak plasma (so‐called ‘Advanced Tokamak Plasma’) is a challenge because of the strong coupling between the current density, the pressure profile and MHD stability. In considering diagnostic needs for the advanced tokamak research, diagnostics for MHD are the most fundamental, since discharges which violate the MHD stability criteria either disrupt or have significantly reduced confinement. This report deals with the development in diagnostic application to control advanced tokamak plasma, with emphasized on recent progress in active feedback control of the current profile and the pressure profile under DEMO‐relevant high bootstrap‐current fraction. In addition, issues in application of the present‐day actuators and diagnostics for the advanced control to DEMO will be briefly addressed, where port space for the advanced control may be limited so as to keep sufficient tritium breeding ratio (TBR).

The diagnostics requirements for the control of NTM instabilities is outlined stressing the importance of correctly managing the estimate uncertainty by the control system. A methodology for the Bayesian assimilation of model predictions and observations is outlined together with an example of application.

The detailed design of the Impurity Influx Monitor (divertor) has been carried out to provide the measurement capability in the harsh environment such as higher irradiation levels of neutron, gamma‐ray and particles than in present devices. The in‐situ calibration system using a micro retro‐reflector array has been developed to monitor the sensitivity change of the optical system due to the environmental effects. The optical alignment system for the Monitor has been developed by using a dedicated optics for alignment in the collection optics for measurement.

A second‐harmonic interferometer based on a CW Nd:YAG laser is presented. The device is extremely compact and versatile and is developed for line‐integrated electron density measurements in large plasma machines. A sensitivity in measuring line‐integrated electron density of 4×1013 cm−2 with time resolution of 8 μs, and 1013 cm−2 with time resolution of 50 μs, is demonstrated.

The size distribution of dust particles present in FTU after disruptions has been evaluated in the range 0.05 μm–0.1 μm using the Thomson scattering system. Rayleigh approximation has been used to estimate the dust size. The distribution, although the radii considered do not differ more than an order of magnitude, behave like a power law. The laser energy density far exceed that necessary to vaporize, at least partially, the particles. This can affect the previous estimate of the particle sizes, and suggests that the effective radii might be larger than the estimated values. A preliminary analysis on the broad band signal is presented.

The Physikalisch‐Technische Bundesanstalt (PTB) has many years of experience with the development, detailed characterization and use of organic liquid scintillation detectors. Such detectors, e.g. NE213, are routinely used as high resolution compact neutron spectrometers in many nuclear experiments. In recent years, a series of measurements with a carefully characterized detector was carried out by PTB in collaboration with ENEA and EFDA‐JET at the Joint European Torus (JET). The results show that these detectors can be used as high resolution compact neutron spectrometers for diagnostic purposes in fusion research. The neutron energy spectrum can be reliably determined from the acquired pulse height spectrum provided the response function of the detector is well determined, a suitable unfolding method is applied and care is taken to ensure stable operation of the system during the measurement. We describe in this paper tests of the performance of the spectrometer carried out at the PTB accelerator. The irradiation facilities at PTB are well suited for such investigations since they allow testing of neutron and photon detectors over a wide range in energy and intensity. Among the reference neutron fields available, there are fields with energies of 2.5 MeV and 14 MeV, produced by means of D(d,n) and T(d,n) reactions. Detailed calculations of the energy spectra have been carried out, and they indicate that the widths of the peaks are comparable to those of thermal fusion plasmas with Maxwellian temperatures of the order of 1 keV. Measurements carried out with a compact neutron spectrometer under fusion‐relevant conditions (i.e., using reference fields with energies of 2.5 MeV and 14 MeV and suitable ranges of count rates and statistics) are discussed in terms of the energy resolution that is achievable and the influence of the different irradiation conditions.

The European Power Plant Conceptual Study (PPCS) has been a study of conceptual designs for commercial fusion power plants. It focused on five power plant models, named PPCS A, B, AB, C and D, which are illustrative of a wider spectrum of possibilities. The PPCS study highlighted the need for specific design and R&D activities as well as the need to clarify the concept of DEMO, the device that will bridge the gap between ITER and the first fusion power plant. An assessment of the PPCS models with limited extrapolations has led to the clarification of the objectives of DEMO. Many parameters will have to be controlled in DEMO in order (1) to control the machine, (2) to satisfy the testing requirements, (3) to satisfy regulatory requirements (primarily safety), and (4) to protect the investment. On the other, DEMO will ulilise one or two plasma scenarios only.

Integrated Data Analysis (IDA) offers a unified way of combining information relevant to fusion experiments. Thereby, IDA meets with typical issues arising in fusion data analysis. In IDA, all information is consistently formulated as probability density functions quantifying uncertainties in the analysis within the Bayesian probability theory. For a single diagnostic, IDA allows the identification of faulty measurements and improvements in the setup. For a set of diagnostics, IDA gives joint error distributions allowing the comparison and integration of different diagnostics results. Validation of physics models can be performed by model comparison techniques. Typical data analysis applications benefit from IDA capabilities of nonlinear error propagation, the inclusion of systematic effects and the comparison of different physics models. Applications range from outlier detection, background discrimination, model assessment and design of diagnostics. In order to cope with next step fusion device requirements, appropriate techniques are explored for fast analysis applications.

During ITER lifetime, dusts and flakes will be produced due to the interaction of plasmas with the in‐vessel materials or due to maintenance. They will be made of carbon, beryllium and tungsten and will be activated, tritiated and chemically reactive and toxic. Safety limits have been set in order to reduce dust hazards. Thus dust diagnostics and removal methods need to be developed for ITER within the constraints linked to magnetic field, radiation, vacuum and temperature. This paper reviews potential diagnostics to monitor the dust content using techniques already used for erosion or deposition monitoring or techniques specially developed for measuring dust in suspension.

Charge eXchange Recombination Spectroscopy (CXRS) will play a crucial role in the diagnosing of burning plasmas: items like helium ash, transport barriers, impurity content or fuel ratio can all be assessed with CXRS. In fact this is the only direct method to obtain information about the light impurity ions, such as temperature, concentrations and rotation, in the core of the plasma. Two of such systems are foreseen at ITER, one in the upper port plug and one on the equatorial level, both viewing the 100 keV diagnostic H-beam. Challenges for this diagnostic development project are: constructing a mirror close to the plasma able to keep its reflectivity under the extreme bombardment by neutrons, erosion by fast neutrals and deposition of sputtered material, design of an optical labyrinth with well enough neutron shielding, developing spectrometers with a throughput about a factor 100 larger than on present day devices, with a similar or better dispersion, calibration and alignment techniques and last but not least, finding ways to obtain the physics relevant information from the measured complicated spectra in real time. With all these issues in mind, an ITER-CXRS pilot experiment has been developed and became operational on the TEXTOR tokamak, to address some of the above aspects. The results of this show the feasibility and the sensitivity of the ITER system: the simulation code for ITER signal levels could be verified, the sensitivity to the current profile has been tested, the beam emission has been compared to beam attenuation calculations and used to obtain absolute impurity concentrations and a high throughput spectrometer became operational.

The absolute measurement of neutron emission rate from the whole plasma is a very important diagnostics as a fusion power monitor in fusion experimental devices with D‐T or D‐T operations. Here measurement techniques of time‐resolved and time‐integrated absolute neutron emission on the present tokamaks and ITER are reviewed. In the present tokamaks, fission chamber installed outside the vacuum vessel are very popular in the absolute neutron emission rate measurement. As well as conventional neutron monitors installed outside the vacuum vessel, in‐vessel neutron monitors using micro fission chamber are proposed for the absolute neutron emission rate measurement in ITER. The neutron activation system provides time‐integrated measurements of the total neutron yield with high accuracy by using well known neutron reaction cross sections, which is useful to maintain a robust measure of fusion energy production with stability and wide dynamic range. The calibration of the relation between the neutron emission ra...

Charge eXchange Recombination Spectroscopy (CXRS) plays a pivotal role in the diagnostics of hot fusion plasmas and is implemented currently in most of the operating devices. In the present report the main features of CXRS are summarized and supporting software packages encompassing “Spectral Analysis Code CXSFIT”, “Charge Exchange Analysis Package CHEAP”, and finally “Forward Prediction of Spectral Features” are described.Beam Emission Spectroscopy (BES) is proposed as indispensable cross‐calibration tool for absolute local impurity density measurements and also for the continuous monitoring of the neutral beam power deposition profile. Finally, a full exploitation of the ‘Motional Stark Effect’ pattern is proposed to deduce local pitch angles, total magnetic fields and possibly radial electric fields.For the proposed active beam spectroscopy diagnostic on ITER comprehensive performance studies have been carried out. Estimates of expected spectral signal‐to‐noise ratios are based on atomic modelling of n...

In this paper we outline the process that is in use for developing the requirements for plasma and first wall measurements on ITER. These requirements are the starting point in the selection, design and integration of the individual measurement systems that together make up the ITER diagnostic system. We describe the issues that have arisen in the defining process and we give the current status. We take a brief forward look at some aspects of the measurement requirements for a next step (DEMO).

The ASDEX Pressure Gauge is, at present, the main candidate for in‐vessel neutral pressure measurement in ITER. Although the APG output is found to saturate at around 15 Pa, below the ITER requirement of 20 Pa. We show, here, that with small modifications of the gauge geometry and potentials settings we can achieve satisfactory behaviour up to 30 Pa at 6 T.

Ensuring appropriate measurements of Alfven eigenmodes in burning plasma experiments will allow the validation of predictions of alpha driven instabilities in plasmas dominated by self heating from fusion produced alpha particles and provide the control capability for optimizing performance, reducing the alpha particle losses due to these modes, and minimizing potential first wall damage. This paper gives a brief overview of several of the relevant Alfven eigenmodes in burning plasma experiments as well as the theoretical tools currently being used to model them. A procedure is then outlined in which predicted Alfven eigenmodes from the ideal MHD code NOVA can be used to simulate the performance of diagnostics on future devices with respect to measurements of these modes. A preliminary application of the technique to ITER's tangential CO2 interferometer is discussed and it is found that the system should be more than adequate to resolve Alfvenic fluctuations with amplitudes in the range of those commonly ...

Diagnostics of the relative concentrations of the atomic and molecular ions were carried out in hydrogen/deuterium plasma with hydrogen/deuterium gas puff in the linear plasma device, TPD‐SheetIV. An omegatron ion mass spectrometer is used for analyzing ion species.

In the era of high power and burning plasma fusion experiments with significant populations of fast particles, the diagnosis of fast ion dynamics becomes an important topic. In ITER, populations of fast ions due to ICRH and NBI, as well as fusion born alphas will carry a significant fraction of the free energy of the plasma. This may affect instabilities and transport in the plasma. A key candidate for diagnosing confined fast ions in ITER is the technique of collective Thomson scattering (CTS). A fast ion CTS system with a probing frequency of 60 GHz has been proposed for ITER. Based on diagnostic experience from particularly TEXTOR and ASDEX Upgrade, work is now progressing towards a final design of a fast ion CTS diagnostic for ITER. The biggest challenge of the diagnostic design is the HFS receiver located in the restricted space behind the blanket modules. Calculations and a series of mock‐up measurements have brought the design towards a four mirror quasi‐optical solution. The development as well as the present design will be presented.

An advanced X‐ray imaging crystal spectrometer is currently under development using a segmented position sensitive detector and time‐to‐digital converter (TDC) based delay‐line readout electronics for burning plasma diagnostics. The proposed advanced XICS utilizes an eight‐segmented position sensitive multi‐wire proportional counter and supporting electronics to increase the spectrometer performance includes the photon count‐rate capability and spatial resolution.

The ITER Tokamak will require many diagnostics both for safe and reliable operation of the machine and for understanding of the physics underlying the performance. The design of these diagnostics raises many challenging technical issues not faced on smaller machines. These arise partly from the increase demands on established diagnostics arising from the increased size, higher magnetic field, large heating power, and in particular the dramatically longer pulse duration of ITER, which make issue such as power loading on first wall components more challenging. The demands on reliability and availability of the machine in order to achieve the objectives within the agreed time schedule also place severe additional demands on the design, quality assurance and maintainability of diagnostics. ITER will produce many orders of magnitude more neutrons than previous Tokamaks and will be a licensed nuclear facility. This has important implications for the traceability, quality assurance and availability of safety critical diagnostics, and for the control of the design and procurement of all diagnostics. The high neutron flux/fluence also constrains the design of diagnostics, which must offer shielding consistent with the allowable dose rates on critical components of the Tokamak, and themselves be tolerant of the radiation level at the diagnostic. This paper presents an overview of the more critical issues for ITER diagnostics.

For future burning plasma experiments, all diagnostics must be re‐evaluated in terms of their measurement capabilities and robustness to the new environment. This is certainly true for interferometry measurements where conventional approaches may not be ideal and interpretation may require modification due to high plasma temperatures. Optimizing these systems to provide maximum information will be crucial to understanding burning plasma dynamics. This paper will explore a variety of phase measurement techniques for the main body and divertor regions that can be utilized on burning plasma experiments like ITER and beyond.

In low temperature plasmas, tokamaks and other experimental fusion devices, the electron temperature and densities in the plasma can be measured with high accuracy by detecting the effect of Thomson scattering of light from a high‐intensity laser fired through the device. It has been established as a robust technique to measure these parameters and in particular it can be used to provide detailed profiles right through the plasma.

Soft‐X ray 2‐D imaging on ITER is not considered yet. We propose a new approach, based on a gas detector with a gas electron multiplier (GEM) as amplifying structure and with a two‐dimensional readout fully integrated with the front end electronics, through an ASIC developed on purpose. The concept has been already tested by means of a prototype, with 128 pixels, carried out in Frascati in collaboration with INFN‐Pisa and tested on FTU in 2001 and NSTX in 2002–2004. Thanks to the photon counting mode, it provides 2‐D imaging with high time resolution (sub millisecond), high sensitivity and signal to noise ratio. Its capability of energy discrimination allows the acquisition of pictures in X‐ray energy bands or to perform a spectral scan in the full energy interval. We propose the realisation of such kind a detector with a readout microchip (ASIC) equipped with 105600 hexagonal pixels arranged at 70 μm pitch in a 300×352 honeycomb matrix, corresponding to an active area of 2.1×2.1 cm2, with a pixel density...

We evaluate using of metal mirrors over‐coated with transparent protection layer for the in‐vessel diagnostic systems in reactor‐grade fusion devices. Ideally, these should satisfy the contradictory demands of high reflectivity and small rate degradation when being bombarded by CX atoms. The serious threat to the performance of diagnostic mirrors is surface contamination with carbon‐based material eroded from carbon tiles. Via coupling the protective layer to a bulk mirror we can mitigate the deposit infiuence on the reflectance spectra. The regards are given to survivability in plasma environment of protected coated metallic mirrors.

Reactors based on DT fusion will impose certain requirements and pose challenges for diagnostics. These relate, for example, to the need for such facilities to address the safety aspects of using tritium and high neutron fluxes leading to activation and radiation fields. There are also implications arising from the need for high machine availability and hence reliability of critical diagnostics. This paper will focus on the safety and licensing implications using design issues for typical diagnostic types to illustrate the above.

In the course of the development of a concept for a spectrally resolving infrared thermography diagnostic for the ITER divertor we have tested 3 types of infrared (IR) fibres in Co60 irradiation facilities under γ irradiation. The fibres were ZrF4 (and HfF4) fibres from different manufacturers, hollow fibres (silica capillaries with internal Ag/AgJ coating) and a sapphire fibre. For the IR range, only the latter fibre type encourages to go further for neutron tests in a reactor. If one restricted the interest onto the near infrared range, high purity core silica fibres could be used. This study might be seen as a typical example of the relation between diagnostic development for a nuclear environment and irradiation experiments.

The use of the neutral particle analysis (NPA) to study the ion component of plasma on ITER has been reviewed. Both thermal (10–200 keV) and supra‐thermal (0.2–4 MeV) energy ranges of neutral fluxes are studied in respect to feasibility of the fusion fuel isotopic composition measurements. Influence of heating neutral beams and diagnostic neutral beam on the measurements is also shown. Possible application of the NPA to measure the energy distribution function of fusion alpha particles is discussed. Low‐ and high‐energy NPA monitors have been proposed for DEMO machine to control the DT fuel isotope ratio.

The operating conditions of a neutron diagnostic systems which are responsible for measuring of the total neutron yield in the ITER tokamak reactor are analyzed. Based on results of neutronic calculations and analysis of suitable methods for measuring the neutron yield, a concept of a system for neutron flux measurement in the divertor is proposed. The design for the neutron flux monitor located in the divertor cassette of the tokamak is selected in view of the requirements specified for the neutron diagnostic system of the ITER and its operating conditions. Several fission chambers with different sensitivities and radiator materials will be used for measurements. System is capable of neutron fluxes measuring over the entire dynamic range of the ITER neutron yield with an error of {delta}

A number of alpha‐particle diagnostics were initiated successfully during the TFTR DT phase. These diagnostics were prototypical and were not able to operate under all conditions. Had TFTR continued to operate, the deficiencies should have been corrected. Effects of radiation on fiberoptics and other components, lack of sufficient power in collective scattering and the effects of neutral beams on pellet ablation impacting pellet charge‐exchange were specific deficiencies in alpha—particle diagnostics. For understanding of the alpha source profile, the importance of very detailed calibrations of neutron diagnostics must be stressed. The interactions of fast ions with instabilities have been taken further in later devices but some aspects were already clear in the DT phase.

The ignition experiment Ignitor will produce high performance plasma regimes with neutron fluxes at the first wall comparable to those expected in power generating reactors (1015n/cm2/s at the first wall). An appreciable degradation of the inorganic insulators surrounding the conductors is expected and the measurement of basic plasma parameters, such as plasma current and position, by electromagnetic diagnostics can become problematic. Thus an R&D program, aimed at the development of effective and affordable devices for electromagnetic diagnostics with higher damage threshold, is being carried out. Prototype diagnostic coils of different shapes have been manufactured, in collaboration with SALENTEC and Università di Lecce. At the same time, an alternative plasma position control method is being explored, based on the diffraction and detection of the soft X-ray radiation emitted, mostly by Molybdenum impurities, near the top or bottom of the plasma column, where the distance of the plasma last closed magnetic surface from the wall is only few millimeters. The underlying principles and general layout of the new system is essentially an adaptation of a 2-dimensional curved crystal spectrometer. © 2008 American Institute of Physics.

A new concept of magnetic pick‐up coil has been developed, aimed at reducing radiation induced thermoelectric effects which could affect the quality of the signals of the magnetic diagnostic for ITER. A winding made of a ceramic‐coated conductor and impregnated with ceramic filler is proposed as an alternative to the Mineral Insulated Cable, presently indicated in ITER reference design. Some prototypes of the new in‐vessel pick‐up coils have been designed, built and tested, to assess the thermoelectric characteristics of the coils.

A key component for the ITER core LIDAR Thomson Scattering (TS) diagnostic would be a detector with good sensitivity in the 850-1060 nm near infrared (NIR) spectral region. Covering this spectral region becomes necessary if a Nd:YAG laser system operating at ? = 1.06 ?m is used as the laser source, which is a very attractive choice in terms of available energy, repetition rate, reliability and cost. In this paper we review the state of the art of two types of detectors available for the above spectral range: the transferred electron (TE) InGaAs/InP hybrid photodiode and the InxGa1-xAs microchannel plate (MCP) image intensifier and we describe the advancements necessary for a possible application in the ITER LIDAR TS. In addition we describe the preliminary characterization of new GaAsP fast MCP photomultipliers (PMTs) suitable for the detection of the visible part of the LIDAR TS spectrum in JET and ITER.