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In order to support the operation of ITER and the planned experimental programme an extensive set of plasma and first wall measurements will be required. The number and type of required measurements will be similar to those made on the present-day large tokamaks while the specification of the measurements—time and spatial resolutions, etc—will in some cases be more stringent. Many of the measurements will be used in the real time control of the plasma driving a requirement for very high reliability in the systems (diagnostics) that provide the measurements. The implementation of diagnostic systems on ITER is a substantial challenge. Because of the harsh environment (high levels of neutron and gamma fluxes, neutron heating, particle bombardment) diagnostic system selection and design has to cope with a range of phenomena not previously encountered in diagnostic design. Extensive design and R&D is needed to prepare the systems. In some cases the environmental difficulties are so severe that new diagnostic techniques are required. a Author to whom any correspondence should be addressed.

This paper presents a detailed study of carbon production and transport from the ergodic divertor (ED) target plates to the plasma core in the Tore Supra tokamak. Adapted experimental and numerical modelling techniques have been used to describe each of the main phenomena in play. Edge electron density and temperature are measured with Langmuir probes. The C II, C III and Hα emission is measured with optical fibres and cameras. The background plasma flow is calculated consistently with the observed recycling pattern by the neutral transport code EDCOLL for the two magnetic connection schemes of interest (short or long connection lengths). 3D Monte-Carlo modelling of carbon near the neutralizer plate (BBQ code) shows that the transport of carbon ions is governed by the friction force in addition to the electric field. Finally, a simplified 3D test particle model is used to estimate the core penetration fraction of carbon. A high value is found for the carbon screening efficiency (fraction of particles that does not penetrate in the plasma core), in the range 95–97% depending on the edge plasma conditions. This value, combined with the calculated carbon influxes, yields the first quantitative estimate of the carbon core contamination during ED operation. The paper shows that the screening of carbon and core contamination are mainly dependent on the carbon source (partially controlled with the ED) and the plasma flow distribution in the laminar region (magnetic topology and particle drifts).

This contribution describes an interpretative integrated-codes model for tokamak co-deposition, which includes as many of the relevant processes as is computationally feasible.

Supporting pilot experiments and activities which are currently considered or already performed for the development of the International Thermonuclear Experiment Reactor active beam spectroscopy diagnostic are addressed in this article. Four key issues are presented including optimization of spectral instrumentation, feasibility of a motional Stark effect (MSE) evaluation based on line ratios, "first-mirror" test-bed experiments at the tokamak TEXTOR, and finally the role of integrated data analysis for the conceptual layout of the change exchange recombination spectroscopy and MSE diagnostic. (C) 2004 American Institute of Physics.

A local analysis technique is presented for the analysis of MSE data to deduce the safety factor q in tokamak discharges. The technique preserves as much as possible the individuality of every single measure by a simple rule of translation of magnetic field pitch angle measurements into q-values. Based on a geometric approach, and the observation that the flux surfaces shapes are strongly constrained by that of the last closed flux surface (LCFS), by the position of the magnetic axis and by a few more global parameters, it provides a robust, nonsubjective, accurate technique that is useful for the experimental study of q-profiles and for the evaluation of its uncertainties. It also provides a useful tool for plasma control experiments as it does not submit data to a preliminary search of minima in a multi-parametric domain, a procedure that may lead to jumps in the time behavior of the produced results.

Upgrade of the Tore Supra ergodic divertor (ED) has led to significant progress in ED physics. Pulse durations of 30?s with LHCD have been achieved demonstrating the heat exhaust capability of both the actively cooled technology at hand and of this specific divertor concept. The disruptive limit governed by the stochastization of the outer magnetic surfaces is found to occur for a value of the Chirikov parameter reaching two on the magnetic surface q = 2+(3/12). This experimentally observed robustness allows one to operate at very low safety factor on the?separatrix (q~2). Numerical analysis of ballooning turbulence in a stochastic layer indicates that the decay of the density fluctuations is associated with an increase of the fluctuating electric drift velocity. This results in an enhanced cross-field transport in the vicinity of the target plates. This lowering of confinement appears to be compensated by an intrinsic transport barrier on the electron temperature. The three-dimensional response of the temperature field is computed with a fluid code. The code can recover the intrinsic transport barrier at the separatrix, reported experimentally, together with small amplitude temperature modulations in the divertor volume. Experimental evidence for the three density regimes (linear, high recycling and detachment) is reported. The low critical density values for transitions between these regimes indicate that similar parallel physics governs the axisymmetric and ED, despite the open configuration of the latter. Measurement and understanding of these density regimes provide a means for feedback control of plasma density and an improvement in ion cyclotron radiofrequency heating coupling scenarios. Experimental data also indicated that particle control with the vented target plates is effective. Increase of both impurity control and radiation efficiency are reviewed. Global power balance has been analysed in order to account for non-axisymmetric radiation. These results, taken together, confirm the large radiation capability of the ED.

A recent extensive experimental study of impurity production and penetration for various density regimes is described. Deuterium and carbon emissions near a neutraliser plate (NP) of the Tore Supra Ergodic Divertor (ED) has been measured with an absolutely calibrated visible endoscope, for high- and low-density plasma regimes. From these radiation measurements, we have deduced an effective carbon flux, and at an order-of-magnitude estimate of the NP erosion: 50 m for the fall 1999 experimental ED campaign (≈500 shots). Combining the measured carbon and deuterium fluxes, we deduce a global experimental carbon sputtering yield for the NP in the range 2×10 −2 –3×10 −1 for ohmic pulses, showing evidence of the importance of carbon self-sputtering.

Three-dimensional (3D) simulations of impurity dynamics in the vicinity of a Tore Supra ergodic divertor neutralizer are presented and compared with spectroscopic observations for a medium density pulse in the high recycling regime. The numerical tool used for the description of impurity generation and transport is a version of the Monte Carlo code BBQ, while the geometry of the magnetic field lines is calculated by use of the MASTOC code. Substantial quantitative consistency is found between the experimental data and our simulations based on recent impurity generation and propagation models. For the given plasma conditions, physical sputtering induced by impact from deuterium ions is found to be the dominant mechanism leading to the carbon contamination of the edge plasma. Chemical sputtering releases a comparable number of carbon impurities from the surface interacting with the plasma but those particles are rapidly re-deposited or pumped away. We find the role of friction of the impurities with the background plasma to be of crucial importance for the determination of the impurity distribution close to the neutralizer. We further find that a flow reversal of the background plasma takes place at the leading edge of the neutralizer with a flow velocity of a few per cent of the ion sound speed in the region that is just clear of the edge.

The transport of light impurity ions is investigated following neon and nitrogen gas puffing in JET ELMy H-mode. Upon achieving consistency among various ion radiation diagnostics through numerical simulations, the experimental ion transport coefficients are compared with the predictions of neoclassical theory at different regions of the plasma. The convection dominates the transport and, in the core, the transport coefficients approach the neoclassical value.

In toroidal magnetic confinement configurations all the charged particles align their magnetic drifts with the flux surfaces if, and only if, the lines of force have zero geodesic curvature (omnigeneous configuration). In this condition, the neoclassical transport is zero; unfortunately, standard tokamak devices are far from meeting such a condition. Nevertheless, a minimization of the geodesic curvature of the lines of force in tokamaks minimizes the neoclassical transport, and could as well reduce any other transport terms depending on the noncoincidence between magnetic and drift surfaces. In particular, the geodesic curvature of the lines of force generates both the neoclassical Pfirsch–Schluter current density j∥PS, as well as Hirshman factor q [Nucl. Fusion 18, 917 (1978)], which increases the moment of inertia of the magnetic configuration. The improved confinement observed in the VH-mode (very high confinement) and in reversed magnetic shear discharges of the DIII-D tokamak [Plasma Physics Contro...

Highly radiative edge layer experiments in Tore Supra ergodic divertor (ED) plasmas are reported. In these experiments, up to 88% of the injected power is radiated in steady state attached plasma conditions. The observed radiated power is higher than the prediction of Matthews' multi-machine scaling. Such behaviour is consistent with the fact that the ratio of the ergodic divertor volume to the main plasma volume is higher for an ergodic divertor than for axisymmetric divertors, or with the enhanced impurity screening observed in Tore Supra. Indeed, a new scaling is derived for impurity radiation in a region of parallel ion transport. It shows that impurity screening is the dominant mechanism controlling divertor radiation, impurity transport along the open field lines having only little influence on P rad .

The extreme ultraviolet (XUV) spectrum of C V and C VI from the edge plasma in JET has been analysed and a collisional radiative model (CRM) is used to simulate the line emissivities. We view, in the XUV range, the scrape-off layer (SOL) during the limiter phase of the discharge evolution, whereas, when the divertor configuration is established, the X-point region is viewed. A zero-dimensional model of the SOL has shown that the line ratios are sensitive to the peripheral profiles (Te, nD fraction and carbon ionization degree) and these parameters are inferred as a function of time for an ohmic JET discharge. We find that charge exchange of carbon ions with deuterium (the filling gas) is an important process in the SOL and near-edge plasma and is included as an integral part of the CRM.

The soft X ray diagnostic at JET views the plasma from six directions with a total of 215 lines of sight. The good coverage of the plasma makes it possible to make detailed tomographic reconstructions of the soft X ray emission during various conditions. One of the tomography methods applied at JET is discussed: a grid based constrained optimization method that uses anisotropic smoothness on flux surfaces as regularization. This method has made it possible to study in detail the transport of heavy trace impurities injected into the plasma by laser blow-off. Impurity injection experiments in hot ion H mode and optimized shear plasmas are presented and discussed. The addition of a number of features to the algorithm, notably a non-negativity constraint, has made it possible to reconstruct very localized soft X ray emission from the wall during edge localized modes (ELMs). The detectors suffer damage from the neutrons produced in deuterium-deuterium (DD) fusion reactions. This damage influences the sensitivity of the detectors, which makes it necessary to cross-calibrate the cameras. A method based on tomographic reconstructions has been developed to achieve the cross-calibration.

The analysis of the contamination of the plasma by a puffed recycling impurity, such as neon, is intrinsically time-dependent and requires simultaneous time-dependent modelling of both the core region and the SOL and divertor region. To this end, a new code, combining core and edge codes, has been developed: its main features will be described and its application to the analysis of an L-mode discharge in which neon was puffed will be shown.

All major JET systems have been fully commissioned for D-T and the DTE1 series of experiments has started with the D-T fuel mixture and operating conditions foreseen for ITER. In the area of ITER physics, significant results have been produced in both D-D and D-T. In D-D, the LH threshold power database has been extended, the bounds on edge-electron temperature and density in ELMy H-modes have been defined and the advantages of Types I and III ELMy discharges have been compared. In D-T plasmas, the isotope effect on H-mode threshold power and transport has been determined so that a more accurate assessment can be made of the ignition margin and heating requirements for ITER. Trace tritium experiments have provided first particle transport measurements and an assessment of the ITER reference ion-cyclotron resonance-frequency heating scenarios has been started, In the area of fusion performance, record D-D neutron yields have been obtained by controlling the plasma and current profiles in hot ion ELM-free H-modes and optimized shear modes. In D-T, internal transport barriers have been readily established in optimized shear discharges and Alfven eigenmodes have been observed.

A power step-down approach leads to extended, high performance operation of deuterium plasmas in the hot ion edge localized mode (ELM)-free H mode of the JET tokamak. ELM-free discharges in JET, when heated steadily at the maximum power available, are usually transient and terminate with a variety of MHD phenomena. With power stepdown, instabilities are delayed or avoided, and nearly constant plasma conditions at up to 10 MJ of stored energy are maintained by 10 MW of heating power for up to 1 s, about an energy confinement time, at 3.5 MA and 3.4 T. No large transient corrections are required for confinement calculations in this hot ion regime, and the energy confinement time scaling is found to be similar to global ELM-free H mode confinement scaling. The confinement times can increase after the transition to quasi-steady conditions, to some 10-25% above the scaling law predictions. Code simulations of the experimentally observed neutron rate and the lack of a major discontinuity in this rate before and after beam power stepdown confirm that neutron production is predominantly (>60%) from thermal fusion. The scaling of fusion rates from deuterium plasmas to deuterium-tritium (DT) mixtures yields a fusion Q approaching 1. After power stepdown, the edge pressure gradient stops increasing and helps delay the onset of instabilities. Giant ELMs still occur, associated with "outer mode" activity and continuously rising plasma density. The plasma remains in an ELM-free H mode even when the heating power after power stepdown is lower than the L-H transition power. Extended operation optimization experiments indicate that stored energy and neutron production are maximized and the density rise minimized by preferentially injecting high energy 140 keV beams after power stepdown

Sophisticated X-ray spectroscopic instruments have been developed and used for confinement studies in tokamaks at JET and Culham Laboratory. The Bragg rotor survey spectrometer, when programmed to operate in monochromatic or limited spectral range (LSR) modes, has been used to derive transport coefficients from the transient spectral signature of injected, non-recycling, test ions. The coefficients appropriate to specific confinement regimes have been investigated with respect to ion charge state and tokamak machine parameters. The LSR mode allows discrimination against background X-:ray light, a particularly serious problem at high electron density, ne ≈ 1020 m−3, in H mode where there is evidence, in COMPASS-D, for modest accumulation of impurities. Impurity ion accumulation is observed most clearly in passive spectroscopic studies of the 1s2 − 1s2p line emission from intrinsic impurity ions such as CI(XVI) using a high resolution Johann configuration crystal spectrometer. Line shapes and line ratios within the limited spectral range 4.45-4.50 A are interpreted in terms of ion and electron temperature and ion fluid velocity. In particular, the ‘q’/‘w’ line intensity ratios are interpreted in terms of the relative abundance of the CI(XV)/CI(XVI) ions which are modelled in terms of ion transport. These continuous, passive measurements of ion confinement are compared with results from the transient injection method. Absolute levels of the X-ray continuum, adjacent to the Cl(XVI) lines, are used to derive Zeff. Both the Bragg and Johann X-ray spectrometers have been calibrated for absolute photon sensitivity. The efficiencies of the diffractors in these instruments can be measured using a newly developed, two-axis goniometer.

This paper presents a spectroscopic study of deuterium and impurity radiation in the MkI divertor of JET in different experimental regimes. Radiated power measurements using absolutely calibrated VUV spectroscopy are consistent with bolometer measurements in a variety of impurity scenarios. These observations, combined with measurements of visible emission, are compared with code predictions of divertor radiation distributions, highlighting uncertainties in the description of the background plasma and of the carbon source, which affect detailed modelling of divertor impurity transport.

Measurements of edge impurity ion parameters have been made in JET neutral beam heated H-modes, using charge exchange spectroscopy. In general there is no evidence of any change in the impurity poloidal velocity at the L to H transition (to within 5 km in the best measurements). The upper limit of the changes in at transition due to changes in poloidal flow is significantly smaller than those seen in smaller devices. Evidence is seen of the rapid formation of a particle transport barrier at the plasma edge and this leads to a modification of the density profile (and also therefore the profile) at the separatrix. In established H-modes an extended region of step density gradient and a gradient in toroidal rotation give a negative well-like structure to .

The results of a series of ITER simulation experiments on JET are described. A series of H-mode threshold experiments are shown to reproduce one of the standard power threshold scaling expressions that is being used to predict the power threshold in ITER. Then, from a series of experiments in which the Larmor radius scaling of ELMy H-modes is examined, it is concluded that the scaling of the confinement is gyro-Bohm-like provided the power levels are well above the threshold. Finally, we show that at high there is a dramatic reduction in the confinement at .

Polarimetry measurements of Faraday rotation on Tore Supra are systematically affected by spurious oscillations that may seriously hinder the reconstruction of plasma current profiles. The same behavior has also been regularly observed on other experiments, such as JET and as RFX. Causes of this phenomenon are interferences between the probing beam and stray radiations having the same frequency. It perturbs the intensity of the signals from the detectors installed on the two orthogonal polarization channels. Experimental tests confirm the dependence of the oscillation amplitudes on the Faraday angle as predicted by the analytical and numerical description of the phenomenon. Special care must be taken to eliminate stray beams: When the stray beam polarization is parallel to the incident one, a relative ratio of the electric field amplitudes

Pellet enhanced performance (PEP) has been observed in a number of JET discharges at various plasma conditions, in both L and H modes, with the H multiplier (the confinement enhancement factor over the Goldston confinement time) covering the range from 1 to 4, and with plasma currents from 1 MA to 4.1 MA. Most of the PEP plasmas have been created by refuelling with pellets of 4 mm diameter injected at 1.2 km/s. PEPs show an improved central confinement with an effective heat conductivity reduced by factors of approximately 2-5 relative to otherwise comparable discharges. This is possibly related to the inverted shear in the plasma core due to the large local bootstrap current density. The limitations in the PEP performance seem to be set by at least two mechanisms: impurity behaviour, MHD activity or a combination of both. In certain discharges, MHD modes seem to be able to check the often observed impurity accumulation. Too much MHD mode activity, however, easily destroys the enhanced confinement of the PEP discharge. The stability of the ballooning modes has been studied and the PEP plasma core is found to be in the second stability region against ballooning modes or close to marginal stability. In a number of discharges complex high (m,n) modes have been observed with the soft X-ray cameras. The behaviour of the low (m,n) MHD modes can only be understood by considering the detailed evolution of the inverted q profile, which exists in a given discharge

The JET neutral beam injection system has proved to be both effective and reliable as a plasma heating device. The ion heating and plasma fuelling characteristics of the system are ideally suited to the production of high fusion performance plasmas while the flexibility in the choice of beam species (H, D, T, 3 He or 4 He) and the ability to inject into almost any JET plasma configuration allows a wide variety of related physics experiments to be carried out. The capability to inject (for the first time) tritium beams was essential to the successful execution of the first tritium experiments in which 1.7 MW of power from DT fusion reactions was generated.

Results are presented of transport studies conducted on trace impurities injected with the laser blow-off technique in a variety of JET L mode pulses. In the core of the discharge, the transport is much slower, the impurity diffusion coefficient D is more than an order of magnitude below the values it assumes further out, but still above the neoclassical predictions. The extent of the slow transport core region varies with the magnetic field and with the total plasma current and is broadly correlated with the edge value of the safety factor. Closer analysis reveals that the current profile is essential in determining the radial dependence of D. This parameter appears to undergo a rapid transition to highly anomalous levels in the vicinity of the radial position where the dimensionless shear parameter is equal to 0.5. Within that region D stays moderate even when the electron temperature gradient is high. A marked increase of D in the outer region of the discharge is observed when the power per particle is raised or, alternatively, when the temperature and its gradient grow in that region, but no clear dependence of D on plasma density is found when the electron temperature profile is kept constant. Transport modelling based on the critical Del Tc assumption leads to D profiles that are similar, although not in detailed quantitative agreement, to the experimental ones when the temperature profiles are flat in the centre; when the temperature profiles are peaked in the centre, even the radial dependence of the predicted diffusion profiles is very different from the one observed. Recent theoretical attempts to analyse the radial structure of the microturbulent fluctuations predict a strong positive dependence of anomalous diffusion on the magnetic shear as observed in our experiments

An account is given of the high performance plasmas established by development of the H-mode regime in JET in the experimental campaigns up to 1992. High performance in this case is measured in terms of the confinement enhancement achieved over the L-mode scaling as measured using the plasma diamagnetism. Three JET H-mode regimes have achieved enhancement factors (H G DIA ) over Goldston L-mode scaling of 2.5 < H G DIA < 4.0. These are the Pellet Enhanced Performance (PEP) H-MODE, the high bootstrap fraction (high β POL ) H-mode and the Hot Ion (HI) H-mode. The phenomenology of these three regimes is reviewed and contrasts and common threads are elucidated

Clostridium difficile infection (CDI) is the leading infective cause of antibiotic associated diarrhea. The principal objective of this study was to assess the knowledge and awareness of internal medicine (IM) residents regarding the epidemiology, clinical recognition, diagnosis and management of CDI.A 20-question survey was distributed to 90 IM residents in all three years of their post graduate training in a university-based program. The survey instrument assessed the resident's knowledge of the current epidemiological trend, clinical recognition and presentation, diagnosis and management of CDI.Forty two out of 90 (48%) residents completed the questionnaire. Only 10/42 (23.8%) of the residents recommended the gold standard investigation for diagnosing CDI. The majority of residents 29/42 (69%) were not aware of the existence of CDI in the outpatient setting and would not test for CDI. Only 50% of the residents were aware of the worse outcome of CDI in inflammatory bowel disease patients and only 12/42 (28.6%) would appropriately risk stratify and treat patients. Almost all of the residents (97.6%) knew about the appropriate time to consult surgery. There was no significant difference in the awareness with respect to the year of training (interns vs. residents), their career choices (primary care vs. fellowship) nor did the knowledge correlate with the United States medical licensing examination (USMLE) scores.IM residents had suboptimal knowledge of many aspects of the common problem of CDI. Educational efforts should be directed at IM residents, many of whom plan careers as primary care/hospitalists, who will encounter patients with CDI.

Preliminary experiments were carried out in the Joint European Torus (JET) using 120 keV helium (He) neutral beam injection (NBI). Injected power levels up to 5 MW with 3He and 7 MW with 4He, lasting up to 3 s were reached. The 3 s helium NBI produced efficient ion heating and similar global and local energy confinements to those obtained with deuterium (D) NBI, in both limiter and X-point plasma geometries, in L-mode and H-mode plasma regimes. The elimination of beam-plasma and beam-beam fusion reactions by replacing D NBI with He NBI extended the range for measuring ion temperatures with the JET neutron profile monitor and neutron spectrometers.

Changes of the toroidal rotation velocity of up to 3*104 m s-1 have been observed during ICRH in JET. The plasma increases its toroidal rotation in the direction of the plasma current. The change in velocity is obtained from the measurement of the Doppler shifted X-ray lines emitted from He-like nickel present in the centre of the plasma. By analyzing various heating scenarios and also measuring the fast anisotropic ion energy content of the plasma the authors conclude the rotation is connected with the creation of fast ions during ion cyclotron resonance heating. Toroidal acceleration of the plasma in connection with MHD instabilities leading to similar magnitude of rotational velocity is also seen.

Impurity transport has been studied in JET using the laser blow-off technique. Results are presented for Ohmic, L-mode and H-mode plasmas. In all cases impurity transport was found to be small inside r/a approximately 0.3 with values for D approximately 0.03-0.3 m2 s-1 close to neoclassical predictions. Outside r/a approximately 0.4, the transport was faster than neoclassical with values for D approximately 0.3-0.6, 3-5 and 0.8-1.2 m2 s-1 in H-mode, L-mode and Ohmic plasmas, respectively. These values apply only between sawtooth crashes, during the sawtooth phase itself ( approximately 100 mu s) the transport is greatly perturbed over the central region allowing the impurities to quickly leave or enter this region. In an Ohmic plasma the impurity confinement time tau imp was between 250 and 350 ms. This value was reduced to approximately 150-200 ms in the L-mode plasma due to an increase of D in the anomalous transport region. During H-mode plasmas, on the other hand, very long impurity confinement times, of the order of several seconds, were observed. This was explained by a sharp increase of the ratio V/D in a thin region near the plasma edge and a general reduction of D in the outer half of the plasma radius.

A zone of reduced anomalous diffusivity for impurities in the central region of the discharge has been reported from several Tokamaks. In this paper the authors point out that this condition is not an occasional occurrence, but a very general feature. Indeed all JET cases analyzed, where the experimental conditions allow adequate sensitivity and space resolution for the measurement of the impurities diffusion coefficient, show unambiguously that this quantity is close to neoclassical levels within r=0.4a. Furthermore, from the analysis of the electron density profile in sawtooth-free phases of JET discharges with moderate electron temperature, the authors deduce that the electron particle diffusivity Dp is also close to neoclassical in the same region. The values obtained for Dp in that region during the early pre-sawtooth phases are the same as in Ohmic post-pellet phases.

Spectral observations of ions of beryllium in the JET plasma are described and are interpreted in terms of the interplay of atomic reactions and local plasma conditions. The methods of generalized-collisional-radiative theory are extended and used to provide a quantitative model. Emphasis is placed on the role of metastable ion states. The diagnostic scope of beryllium observations is explored for the influx ions Be0+ and Be1+ in the visible spectral range, for Be2+ in the XUV, and for Be3+ by charge exchange spectroscopy. Useful results for general diagnostic interpretation are presented in tables and graphs. The calculation procedures and data form part of the 'Atomic Data and Analysis Structure' in use at JET.

Observations of the JET tokamak are used to illustrate contrasting spectral emission from a range of plasma environments differing in temperature, density, interaction with boundary surfaces, dynamic state and excitation mechanisms. Some spectral features of diagnostic value are identified. Models based on collisional radiative theory are used to investigate these features. The generality of this approach to modelling the radiating properties of atoms in arbitrary dynamic plasmas is indicated.

Small quantities of medium-Z and high-Z impurities were injected into JET plasmas and their progression was followed by two soft X-ray cameras with good spatial and temporal resolution. The results show that the transport of impurities is much slower in the central region of the plasma than outside of it and that it is greatly enhanced during sawtooth crashes. Simulation of the evolution of the emissivity profiles using an impurity transport code yielded values for the radially dependent transport coefficients; in particular, these values were compared for cases of ohmically heated plasmas and RF heated plasmas.