[en] TRANSP is a time dependent transport analysis code. Experimental data is used wherever possible to define plasma parameters, and models similar to those found in simulation codes are used to supplement this data. TRANSP first solves the magnetic field diffusion equation and then uses the particle and energy conservation equations to calculate local transport coefficients. The code also produces simulations of certain diagnostic measurements which can be used as consistency checks. Obtaining good results from TRANSP is strongly dependent on the reliability of the experimental data and on an understanding of the limitations of the various diagnostic measurements. This report contains a detailed discussion of a typical transport analysis. Section II describes the various experimental data which can be provided as input to TRANSP either through a namelist or in a user PPF and indicates the relative importance of specific data in a simulation. Section III gives details of some of the additional physical quantities which must be defined before running TRANSP and some of the controls that are available to determine the way in which the data is used within the code. Section IV is a description of a full transport analysis of a typical JET H-mode shot. Section V contains conclusions and general remarks on transport analysis using TRANSP. (Author)

[en] The scaling of the energy confinement in H-mode plasmas with different hydrogenic isotopes (H, D, D-T and T) is investigated in JET. For ELM-free H-modes the thermal energy confinement time τ_th is found to decrease weakly with the isotope mass (τ_th ∼ M^-0.25±0.22) whilst in ELMy H-modes the energy confinement time shows practically no mass dependence (τ_th ∼ M^0.03±0.1). Detailed local transport analysis of the ELMy H-mode plasmas reveals that the confinement in the edge region increases strongly with the isotope mass whereas the confinement in the core region decreases with mass (τ_thcore ∝ M^-0.16 ) in approximate agreement with theoretical models of the gyro-Bohm type (τ_gB ∼ M^-0.2). (author)

[en] An experiment has been performed at the Joint European Torus (JET) which has demonstrated clear self-heating of a deuterium-tritium plasma by alpha particles produced in fusion reactions. Since the alpha power was approximately 10% of the total power absorbed by the plasma, the heating was distinguished from other changes, due to isotopic effects, by scanning the plasma and neutral beam mixtures together from pure D to nearly pure T in a hot ion H-mode with 10.5 MW neutral beam power. At an optimum mixture of 60 ± 20% T, the fusion gain (= P_fusion / P_absorbed) was 0.65 and the alpha heating showed clearly as a maximum in electron temperature. The change in temperature produced by alpha heating was ΔT_e(0)= 1.31 ± 0.23 keV in 12.2 keV. The effect of the heating could also be seen in the ion temperature and energy content. (author)

[en] In current large tokamaks non-intrinsic seeded impurities have been used to produce divertor power loads which would be considered acceptable when extrapolated to ITER. Many devices have achieved the goal of high fractional radiated powers, small frequent ELMs and detachment which are characteristic of radiative H-mode regimes. However, it has been a matter of concern that the Z_eff associated with the seeded impurities may exceed that allowable in ITER and also that the degradation in energy confinement may be unacceptable. Confidence can only be built in the prediction of these parameters in ITER if reliable scalings are available for impurity content and energy confinement which have a sound physics basis. This paper describes work at JET in this area whilst using multi-machine data to characterise the size scaling and provide a context for the JET data. Predicted levels for the impurity content of seeded ITER plasmas appear to be of marginal acceptability. The situation with regard to confinement is less clear. Dimensionless parameter scaling experiments have been conducted in which β, q₉₅, fractional radiated power and Z_eff are held constant for a range of ρ*. The scaling of global energy confinement derived from these radiative discharges appears to be Bohm-like. However, local transport analysis of JET pulses using the TRANSP code suggests that the effective thermal diffusivity of the core retains its gyro-Bohm like scaling. (author)

[en] Because of its large size, single null divertor, and flexible magnetic geometry, JET is capable of producing the most reactor-relevant plasmas of any present generation tokamak. In the recent deuterium- tritium experiments the fusion performance of these plasmas was tested for the first time. Over 4 MW of fusion power was produced in a high power, steady state pulse of 5 s, limited by the duration of the heating power. The fusion Q^E, defined simply as the fusion energy produced divided by the input energy over this 5 s interval, was 0.18. The performance of our DT ELMy H-mode discharges extrapolates to ignition in ITER and thus provides increased confidence in its current design. Operation at low q₉₅ is possible in JET with no degradation in confinement and provides an improved margin to ignition when extrapolated to ITER. (author)

[en] High power combined NB+ICRF (H)D heating experiments have been carried out in the JET MKIIa divertor configuration, both in deuterium (DD) and in deuterium-tritium (DT) plasmas. Results from a wide range of RF injected power, up to 9.5 MW, NB power up to 22 MW, plasma currents, up to 4.2 MA, and toroidal field values, up to 3.6 T, show a clear improvement in electron temperature, DD reactivity and stored energy with respect to NB only discharges. High energy Neutral Particle Analyser (NPA) data show that acceleration of the NB injected Deuterons takes place at the second harmonic deuterium resonance. This is confirmed by numerical simulations with the PION code. Experiments have also been carried out in the (He³)D heating scenario. ICRF heating has been an essential ingredient in the DT experiments in the ELM-free Hot-Ion regime, contributing to the achievement of a record fusion power of 16.1 MW and a record stored energy of 17 MJ. (author)

[en] The concept of nondimensional scaling of transport makes it possible to determine the required size for an ignition device based upon data from a single machine and illuminates the underlying physics of anomalous transport. The scaling of cross-field heat transport with the relative gyroradius ρ*, the gyroradius normalized to the plasma minor radius, is of particular interest since ρ* is the only nondimensional parameter which will vary significantly between present day machines and an ignition device. These nondimensional scaling experiments are based upon theoretical considerations which indicate that the thermal heat diffusivity can be written in the form χ = χ_Bρ*^x_ρ F(β, v*, q, R/a, κ, T_e/T_i,...), where χ_B = cT/eB. As explained elsewhere, x_ρ = 1 is called gyro-Bohm scaling, x_ρ is Bohm scaling, x_ρ = -1/2 is Goldston scaling, and x_ρ = -1 is stochastic scaling. The DIII-D results reported in this paper cover three important aspects of nondimensional scaling experiments: the testing of the underlying assumption of the nondimensional scaling approach, the determination of the ρ* scaling of heat transport for various plasma regimes, and the extrapolation of the energy confinement time to future ignition devices

[en] Analysis of a high performance plasma in JET has uncovered large abrupt changes in confinement. The change in the plasma configuration at these times is small and it appears that the confinement is not determined by the macroscopic plasma parameters

[en] In current large tokamaks, non-intrinsic seeded impurities have been used to produce divertor power loads which would be considered acceptable when extrapolated to ITER. Many devices have achieved the goals of high fractional radiated powers, small frequent ELMs and detachment which are characteristic of radiative H mode regimes. The influence of divertor geometry on these characteristics is described. It has been a matter of concern that the Z_eff associated with the seeded impurities may exceed that allowable in ITER and also that the degradation in energy confinement may be unacceptable. Confidence can only be built in the prediction of these parameters in ITER if reliable scalings are available for impurity content and energy confinement which have a sound physics basis. Work is described at JET in this area whilst using multi machine data to characterize the size scaling and provide a context for the JET data. Predicted levels for the impurity content of seeded ITER plasmas appear to be of marginal acceptability. Discharges run in the JET Mark I, Mark IIA and Mark IIAP divertors are compared and indicate that increased divertor closure has brought relatively minor benefits in highly radiative discharges. The acceptability of the energy confinement of radiation for ITER remains unclear. Dimensionless parameter scaling experiments have been conducted in which β, q₂₅, fractional radiated power and Z_eff are held constant for a range of ρ_*. The price paid for high edge radiation and small ELMs appears to be a 25% loss in total stored energy as a result of edge pedestal degradation. However, the underlying energy confinement scaling may still be consistent with gyro-Bohm scaling, which would give an adequate margin for ITER. This conclusion is, however, sensitive to the scaling of confinement with collisionality, which is difficult to determine due to the coupling between ρ_* and ν_* which is a consequence of radiation dominated regimes. (author)

[en] The analysis of discharges with strong on- and off-axis ion cyclotron resonance during heating shows that the transport of heat in JET is local and diffusive. Discharges with or without pellet injection are considered; in all cases, the electron temperature profile responds to the location of the heating. The total heat flow Q can be described by a local diffusive model of the form Q = χ(q_ψ, module ∇ T_e) n_e ∇ T_e, where χ is proportional to q^1.75_ψ and increases with modul ∇ T_e. Several forms of the dependence of χ on ∇ T_e are shown to give a reasonable fit to the data. (author). Letter-to-the-editor. 9 refs, 10 figs