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Alarge superconducting machine, JT-60SA has been constructed to provide major contributions to the ITER program and DEMO design. For the success of the ITER project and fusion reactor, understanding and development of plasma controllability in ITER and DEMO relevant higher beta regimes are essential. JT-60SA has focused the program on the plasma controllability for scenario development and risk mitigation in ITER as well as on investigating DEMO relevant regimes. This paper summarizes the high research priorities and strategy for the JT-60SA project. Recent works on simulation studies to prepare the plasma physics and control experiments are presented, such as plasma breakdown and equilibrium controls, hybrid and steady-state scenario development, and risk mitigation techniques. Contributions of JT-60SA to ITER and DEMOhave been clarified through those studies. Peer Reviewed Article escrit per 127 autors/autores: M Yoshida, G Giruzzi, N Aiba, J F Artaud, J Ayllon-Guerola, L Balbinot, OBeeke, E Belonohy, P Bettini, W Bin, A Bierwage, T Bolzonella, M Bonotto, CBoulbe, J Buermans, M Chernyshova, S Coda, R Coelho, S Davis, C Day, GDeTommasi, M Dibon, A Ejiri, G Falchetto, A Fassina, B Faugeras, L Figini, M Fukumoto, S Futatani, K Galazka, J Garcia, M Garcia-Muñoz, L Garzotti, L Giacomelli, L Giudicotti, S Hall, N Hayashi, C Hoa, M Honda, K Hoshino, M Iafrati, A Iantchenko, S Ide, S Iio, R Imazawa, S Inoue, A Isayama, E Joffrin, K Kamiya, Y Ko, M Kobayashi, T Kobayashi, G Kocsis, A Kovacsik, T Kurki-Suonio, B Lacroix, P Lang, Ph Lauber, A Louzguiti, E de la Luna, G Marchiori, M Mattei, A Matsuyama, S Mazzi, A Mele, F Michel, Y Miyata, J Morales, P Moreau, A Moro, T Nakano, M Nakata, E Narita, R Neu, S Nicollet, M Nocente, S Nowak, F P Orsitto, V Ostuni, Y Ohtani, N Oyama, R Pasqualotto, B Pégourié, E Perelli, L Pigatto, C Piccinni, A Pironti, P Platania, B Ploeckl, D Ricci, P Roussel, G Rubino, R Sano, K Särkimäki, K Shinohara, S Soare, C Sozzi, S Sumida, T Suzuki, Y Suzuki, T Szabolics, T Szepesi, Y Takase, M Takech, N Tamura, K Tanaka, H Tanaka, M Tardocchi, A Terakado, H Tojo, T Tokuzawa, A Torre, N Tsujii, H Tsutsui, Y Ueda, H Urano, M Valisa, M Vallar, J Vega, F Villone, T Wakatsuki, T Wauters, M Wischmeier, S Yamoto, L Zani

This paper suggests the use of two optical elements for laser transfer in Thomson scattering diagnostics, which are widely used for other laser applications. YAG lasers amplified by flash lamps (repetition frequency of 50–100 Hz having a few Joules output) can sometimes have adverse effects such as peaked beam profiles and wavefront distortion. We used a beam homogenizer, which is a refractive optical element, to change the beam profile from peaked to non-peaked at a designated position. Using a super-Gaussian output profile when amplifying lasers facilitated longer—by a factor of 1.5 (=300 mm/200 mm) compared with top-hat beam profile—sustained distances, i.e. the distance along the laser path having a non-peaked profile. In terms of beam quality, wavefront distortion broke the beam profile in the far field. We used a deformable mirror to correct and flatten the wavefront of the beam. A YAG laser having a wavefront distortion of 0.46λ peak-to-valley was used to test the application of the deformable mirror, the results of which improved wavefront distortion to a wavelength of 0.1λ peak-to-valley.

Two types of back scattering systems are utilized for high temperature fusion plasma turbulence study. W-band backscattering system is used for measuring the electron Larmor radius scale turbulence and around Q-band frequency comb Doppler backscattering system have been designed for measuring the ion Larmor radius scale turbulence.

A fast charge exchange recombination spectroscopy (CXRS) system has been developed for the real-time measurement and feedback control of ion temperature ( T i ) profile and toroidal rotation velocity ( V t ) in JT-60U. In order to control T i and V t in real-time, the charge exchange recombination spectroscopy with high time resolution, the real-time processor system, and the real-time control system have been developed. Utilizing this system, real-time control of the T i gradient between r / a ∼ 0.25–0.5 has been demonstrated with neutral beams at high beta plasmas (normalized beta β N ∼ 1.6–2.8). The strength of the internal transport barrier is controlled. Moreover, the real-time control of V t has been demonstrated from counter (anti-parallel to the plasma current, I p ) to co (parallel to the I p ) direction. Then the behavior of edge localized mode (ELM) is changed by controlling the V t .

The concept for a compact DEMO reactor named 'SlimCS' is presented. Distinctive features of the concept are low aspect ratio (A = 2.6) and use of a reduced-size centre solenoid (CS) which has the function of plasma shaping rather than poloidal flux supply. The reduced-size CS enables us to introduce a thin toroidal field coil system which contributes to reducing the weight and perhaps lessening the construction cost. Low-A has merits of vertical stability for high elongation (κ) and high normalized beta (βN), which leads to a high power density with reasonable physics requirements. This is because high κ facilitates high nGW (because of an increase in Ip), which allows efficient use of the capacity of high βN. From an engineering aspect, low-A may ensure ease in designing blanket modules robust to electromagnetic forces acting on disruptions. Thus, a superconducting low-A tokamak reactor such as SlimCS can be a promising DEMO concept with physics and engineering advantages.

The characteristics of momentum transport and plasma rotation in the toroidal direction are studied, using near-perpendicular neutral beam injection (PERP-NBI), co tangential and counter (CTR) tangential NBI in JT-60U. Diffusive and non-diffusive terms of momentum transport are evaluated from the transient analysis by using the momentum source modulation. Fast ion losses due to the toroidal field ripple, which locally induces the edge CTR rotation, are used as a novel momentum source. Parameter dependence of these transport coefficients i.e. the toroidal momentum diffusivity (?) and the convection velocity (Vconv), and the relation between momentum and heat diffusivities (?i) are investigated in L-mode plasmas systematically. The toroidal momentum diffusivity increases with increasing heating power and decreases with increasing plasma current. The relation of ? and ?i to some non-dimensional parameters is investigated. A clear dependence of ?/?i on normalized plasma pressure (?N) is observed. It is also found that toroidal rotation velocity profiles in the case with and without external torque input can be almost reproduced by ? and Vconv estimated from the transient momentum transport analysis at low ? (?N < 0.4).

Results of active control of neoclassical tearing modes (NTMs) by electron cyclotron current drive (ECCD) in JT-60U are described. Growth of an NTM with poloidal mode number m = 3 and toroidal mode number n = 2 has been suppressed by ECCD inside the sawtooth inversion radius in the co-direction, showing the possibility of the coexistence of sawtooth oscillations and a small-amplitude m/n = 3/2 NTM without large confinement degradation. Stabilization of an m/n = 2/1 NTM by ECCD at the mode rational surface has been demonstrated with a small ratio of the current density driven by the electron cyclotron (EC) wave to the local bootstrap current density (∼0.5). In addition, dependence of the stabilization effect on ECCD location has been investigated in detail. It has been found that an m/n = 2/1 NTM can be completely stabilized with the misalignment of the ECCD location less than about half of the full island width, and that the m/n = 2/1 NTM is destabilized with the misalignment comparable to the full island width. Time-dependent, self-consistent simulation of magnetic island evolution using the TOPICS code has shown that the stabilization and destabilization of an m/n = 2/1 NTM are well reproduced with the same set of coefficients of the modified Rutherford equation. The TOPICS simulation has also clarified that EC wave power required for complete stabilization can be significantly reduced by narrowing the ECCD deposition width.

Edge localized mode (ELM) measurements in many tokamaks, including ASDEX-Upgrade, DIII-D, JET, JT-60U and MAST, are reviewed, which includes progress in experimental observations at the plasma edge region by means of fast-time resolved diagnostics with high precision, such as scanning probe, radial interferometer chord, BES and tangentially viewing fast-gated camera at the midplane. ELM dynamics data show that the majority of the ELM particle and energy transport should be dominated by ion convection physics and associated timescales. Furthermore, recent diagnostic upgrades on many tokamaks reveal the ELM filament structure and their complex motion towards radial, poloidal and toroidal directions. Approaches to control the Type-I ELMs, in addition to the alternative scenarios to Type-I ELMy H-mode operation (so-called, small/no ELM regimes) are also a key area of research for current tokamaks, which demonstrated a high confinement (being comparable to that of Type-I ELMy H-mode plasmas at similar parameters) in the absence of large, ELM induced, transient heat/particle fluxes to the divertor targets. Although tolerable ELM regimes are obtained in existing devices, their application to ITER is uncertain. Issues of these regimes towards further experiments and power deposition on divertor targets and main chamber wall are discussed.

The driving mechanism of toroidal rotation and the momentum transport are studied on JT-60U in relation to the toroidal rotation in the direction antiparallel to the plasma current, i.e. counter (CTR) direction, with near-perpendicular neutral beam (PERP-NB) injection. Fast ion losses due to the toroidal field ripple induce CTR rotation in the peripheral region, and the magnitude of CTR rotation with PERP-NBs reduces by installing the ferritic steel tiles as a consequence of the reduction in the ripple losses. It is also found that toroidal rotation velocity profiles in the core region can be explained by momentum transport considering diffusivity and convective velocity estimated from transient momentum transport analysis in L-mode plasmas.

By conducting power scan experiments in three cases of toroidal field ripple configurations (δ r ≃ 0.4, 1.0 and 2.0%) with variation of the toroidal momentum source (co, balanced, counter) relative to the direction of the plasma current, the roles of the loss of fast ions and toroidal rotation on the H-mode pedestal structure were investigated. It was found that the pedestal pressure was increased with a decrease in fast ion loss power. On the other hand, the variation in toroidal rotation did not affect strongly the pedestal pressure, although the loss of fast ions due to existing large toroidal field ripple forced the toroidal rotation basically to the counter direction in JT-60U. Due to the enhanced counter toroidal rotation induced by the loss of fast ions, similar V tor profiles were obtained for discharges with different toroidal momentum source and loss of fast ions. When the loss of fast ions became smaller, pedestal density was raised remarkably while there was no significant difference in the temperature profiles.

Effects of plasma rotation and losses of fast ions on Type-I ELM characteristics have been systematically studied in the JT-60U tokamak, scanning combinations of NBI (tangential co-, balanced- and counter-NBI plus perpendicular NBI) in the three types of plasma configurations (corresponding toroidal field ripple at the plasma edge, δ r ∼0.4, 1.0 and 2.0%). New findings on the Type-I ELM characteristics are as follows: smaller ELM energy loss normalized by pedestal stored energy, ΔW ELM /W ped , and faster ELM frequency, f ELM , are confirmed in the counter-NBI in comparison with the co-NBI discharges. Nevertheless, the power loss due to ELM, P ELM (= ΔW ELM × f ELM ), normalized by heating power crossing the separatrix, P SEP , is constant regardless of the direction of the momentum injection at each plasma configuration. In contrast, the P ELM /P SEP decreases with increasing δ r . The relationship between ELMs, rotation and the losses of fast ions are discussed.

This report summarizes Type I edge localized mode (ELM) dynamics measurements from a number of tokamaks, including ASDEX-Upgrade, DIII-D, JET, JT-60U and MAST, with the goal of providing guidance and insight for the development of ELM simulation and modelling. Several transport mechanisms are conjectured to be responsible for ELM transport, including convective transport due to filamentary structures ejected from the pedestal, parallel transport due to edge ergodization or magnetic reconnection and turbulent transport driven by the high edge gradients when the radial electric field shear is suppressed. The experimental observations are assessed for their validation, or conflict, with these ELM transport conjectures.

Comparisons of H-mode regimes were carried out on the Alcator C-Mod and JFT-2M tokamaks. Shapes were matched apart from aspect ratio, which is lower on C-Mod. The high recycling steady H-mode on JFT-2M and enhanced D-alpha (EDA) regime on C-Mod, both of which feature very small or no ELMs, are found to have similar access conditions in q 95 - v* space, occurring for pedestal collisionality v* ? 1. Differences in edge fluctuations were found, with lower frequencies but higher mode numbers on C-Mod. In both tokamaks an attractive regime with small ELMs on top of an enhanced D α baseline was obtained at moderate v* and higher pressure. The JFT-2M shape favoured the appearance of ELMs on C-Mod and also resulted in the appearance of a lower frequency component of the quasicoherent mode during EDA.

Stabilization of an m = 3/n = 2 neoclassical tearing mode (NTM) by a local electron cyclotron current drive (ECCD) has been studied in high βp ELMy H-mode plasmas in the JT-60U tokamak. In the stabilization experiment, the electron cyclotron (EC) injection timing is scanned from the 'before mode onset' phase (preemptive ECCD) to the mode saturation phase (late ECCD). It has been demonstrated that the ECCD is more effective when it is applied before the mode onset and the critical timing for effective ECCD is related to the mode excitation phase. The EC power to prevent the 3/2 NTM excitation by preemptive ECCD is lower by about 20% compared with complete stabilization by late ECCD. Even when the 3/2 NTM is excited, the stabilization effect is stronger than for late ECCD. For a high performance plasma of the normalized beta, βN = 3.0, the H-factor H89PL improves from 1.9 to 2.1 when the 3/2 NTM is suppressed. A numerical study has been made based on the modified Rutherford equation coupled with a 1.5D transport code and an EC code. The simulation reproduces well the time evolution of the magnetic island both at the growing and stabilizing phases. The simulation results show that it is important to adjust not only the EC current position but also its width to stabilize the NTM effectively. The reduction of EC power for NTM prevention in experiments for preemptive ECCD can be explained by the increase of the minimum seed island size for NTM excitation.

Since it is uncertain if ITER operation is compatible with type-l edge localized modes (ELMS), the study of alternative ELM regimes is an urgent issue. This paper reports on experiments on JET aiming to find scenarios with small ELMS and good confinement, such as the type-II ELMS in ASDEX Upgrade, the enhanced D-alpha H-mode in Alcator C-mod or the grassy ELMS in JT-60U. The study includes shape variations, especially the closeness to a double-null configuration, variations of q(95), density and beta poloidal. H-mode pedestals without type-I ELMs have been observed only at the lowest currents (

This paper reports the results of the progress in stationary discharges with a large bootstrap current fraction in JT-60U towards steady-state tokamak operation. In the weak shear plasma regime, high-βp ELMy H-mode discharges have been optimized under nearly full non-inductive current drive conditions by the large bootstrap current fraction (fBS ~ 45%) and the beam driven current fraction (fBD ~ 50%), which was sustained for 5.8 s in the stationary condition. This duration corresponds to ~26τE and ~2.8τR, which was limited by the pulse length of negative-ion-based neutral beams. The high confinement enhancement factor H89 ~ 2.2 (HH98y2 ~ 1.0) was obtained and the profiles of current and pressure reached the stationary condition. In the reversed shear plasma regime, a large bootstrap current fraction (fBS ~ 75%) has been sustained for 7.4 s under nearly full non-inductive current drive conditions. This duration corresponds to ~16τE and ~2.7τR. The high confinement enhancement factor H89 ~ 3.0 (HH98y2 ~ 1.7) was also sustained, and the profiles of current and pressure reached the stationary condition. The large bootstrap current and the off-axis beam driven current sustained this reversed q profile. This duration was limited only by the duration of the neutral beam injection.

Bursting modes in the frequency range of the toroidicity induced Alfv?n eigenmode are observed in the plasma to which the negative-ion-based neutral beam (N-NB) is injected. A bursting mode changes its frequency by 10-20?kHz in 1-5?ms and is called fast frequency sweeping (fast FS) mode. Another bursting mode evolves explosively in ?400??s and is called an abrupt large-amplitude event. The dependence of their saturation level was compared?with the experimentally observed growth rate and damping rate. The mode amplitude increases with the observed growth rate for fast FS modes. The modes with large amplitude and a large enhanced transport were observed when a large neutron emission rate was observed. The burst period increases as the drop ratio of the neutron emission increases.

A three-channel heterodyne O-mode reflectometer system has been developed for density fluctuation measurements on the JT-60U tokamak. The system consists of one fixed channel with a frequency of 34 GHz and two selectable frequency channels with frequencies in the range of 34–40 and 48–50 GHz in order to measure the change of fluctuation amplitude, fluctuation coherence, and movement of the cutoff layer during the discharge. The reflectometer system has now become a standard diagnostic for density fluctuation measurements on JT-60U covering both core and edge plasma regions. The capabilities of the system are illustrated for three experimental cases: edge transport barriers in H-mode plasmas, internal transport barriers in reversed shear plasmas, and fast turbulence burst at the onset of multifaceted asymmetric radiation from the edge.

In GAMMA 10, the radiation pattern of a heating wave of fundamental ECRH for potential formation was not axi-symmetric but vertically elongated on the resonance surface. The non-axisymmetric radiation pattern caused a non-axisymmetric potential profile and likely induced a radial loss. Then, the radiation pattern has been axi-symmetrized. Accordingly, an almost axi-symmetric potential profile has been obtained and a large density increase during ECRH has been observed in the central cell. This implies that radial losses associated with ECRH have been substantially reduced. A new antenna has recently been installed for additional plug electron heating (second ECRH). With this antenna, a larger power and/or a longer pulse width have become available. In a most recent experiment, we have succeeded in axial plugging with a duration up to 0.15 s by sequential use of the usual ECRH and the second ECRH. Moreover, there is an indication that the second ECRH is more desirable for further reduction of the radial loss.

Required basic features as to 30 Gbpsi recording density for write head are good overwrite O/W, good nonlinear transition shift NLTS, and high frequency performance in half-micron track width. To achieve these, we have developed a new structure, planar yoke write head, combined with SV read head, which features narrow track (physical write track width=0.35 /spl mu/m), narrow coil pitch (1.3 /spl mu/m coil pitch) for short yoke length (16 /spl mu/m yoke length), one-layer coil design, and used flat yoke pole while succeeding in the advantages of our current stitched pole write head. Regarding the write performance, we compared planar yoke head with current stitched pole head by simulation and actual measurement.

A millimetre wave two-dimensional detector array has been newly developed for application to a phase-imaging interferometer installed in the GAMMA 10 tandem mirror. The interferometer consists of two sources and a quasi-optical transmission system. The transmitted wave is mixed with the local oscillator (LO) wave to provide a 150 MHz intermediate frequency (IF) signal. The detector has 4 × 4 channels consisting of beam-lead GaAs Schottky barrier diodes bonded to bow-tie antennas fabricated using photolithographic techniques on a fused quartz substrate of size 38.1 mm × 38.1 mm. The interferometer successfully measures the time evolution of line density profiles with a phase resolution of less than 1 200 fringe and a spatial resolution of 16 mm in the vertical direction and 5 mm in the horizontal direction. The system is also applied to the measurement of electron cyclotron emission (ECE) as a heterodyne radiometer. The axial and radial dependence of the second-harmonic ECE is observed simultaneously. The fluctuation spectra of the ECE signals are compared with those obtained from the interferometer.

Reflectometric techniques have been applied to the GAMMA 10 tandem mirror to measure density and magnetic fluctuations associated with electromagnetic plasma waves in the ion cyclotron range of frequency (ICRF). The excitation and propagation of ICRF-driven waves are studied by reflectometers in order to achieve efficient heating of plasmas. The radial profile of the fluctuation level is expected to give the deposition profile of the heating power. A cross-polarization scattering diagnostic system is also installed in the central cell of GAMMA 10. An incident ordinary (extraordinary) wave is converted to an extraordinary (ordinary) wave by magnetic fluctuations. The converted wave can propagate through a cut-off layer and reach the detector. The level of magnetic fluctuation (about 10 −4 ) is evaluated for the ICRF-driven waves.

The role of electron cyclotron resonance heating (ECRH) on the toroidal rotation velocity profile has been investigated in the JT-60U tokamak device by separating the effects of the change in momentum transport, the intrinsic rotation by pressure gradient, and the intrinsic rotation by ECRH. It is found that ECRH increases the toroidal momentum diffusivity and the convection velocity. It is also found that ECRH drives the codirection (co) intrinsic rotation inside the EC deposition radius and the counterdirection (ctr) intrinsic rotation outside the EC deposition radius. This ctr rotation starts from the EC deposition radius and propagates to the edge region.

The elastic neutron-scattering experiments were carried out on the solid solutions ${\text{CeRh}}_{1\ensuremath{-}x}{\text{Co}}_{x}{\text{In}}_{5}$ to clarify the nature of the antiferromagnetic (AF) state in the vicinity of the quantum critical point: ${x}_{c}\ensuremath{\sim}0.8$. The incommensurate AF order with the wave vector of ${q}_{h}=(1/2,1/2,\ensuremath{\sim}0.3)$ observed in pure ${\text{CeRhIn}}_{5}$ is weakly suppressed upon doping with Co, and a commensurate ${q}_{c}=(1/2,1/2,1/2)$ and an incommensurate ${q}_{1}=(1/2,1/2,\ensuremath{\sim}0.42)$ AF structures evolve at intermediate Co concentrations. The AF orders with ${q}_{c}$ and ${q}_{1}$ are enhanced at $x=0.7$, and furthermore, the ${q}_{h}$ AF order vanishes. These results suggest that the AF correlations with the ${q}_{c}$ and ${q}_{1}$ modulations are significantly enhanced in the intermediate $x$ range, and may be connected with the evolution of the superconductivity observed above $x\ensuremath{\sim}0.3$.

We performed elastic neutron scattering experiments on solid solution CeRh1-xCoxIn5 with x=0.4 to clarify the nature of the antiferromagnetic (AF) phase in the vicinity of the quantum critical point. We observed the incommensurate AF order below T_Nh=3.5 K. The structure of the incommensurate AF order is basically unchanged from that for pure CeRhIn5. We further found the evolution of a new commensurate AF order with the modulation of q_c=(1/2,1/2,1/2) below T_Nc=2.9 K. The volume-averaged moments for the incommensurate and commensurate AF phases are 0.38 mu_B/Ce and 0.21 mu_B/Ce, respectively, which are reduced from the incommensurate AF moment (0.75 mu_B/Ce) for pure CeRhIn5. We suggest from these results that the commensurate magnetic correlation may be tightly coupled with the superconductivity observed below T_c=1.4 K., 5 pages, 4 figures, to appear in J. Phys. Soc. Jpn

In magnetically confined plasmas, the applicaton of radio frequency (RF) waves is considered to be one of the most promising methods for additional heating in present and future thermonuclear fusion experiments such as ITER. The physics of wave excitation and propagation in the ion cyclotron range of frequency (ICRF) is under intensive experimental and theoretical investigation for efficient heating. The ICRF-wave studies have also been performed for understanding mechanisms associated with a variety of processes such as Alfven wave current drive,1 RF-induced radial transport,2 RF stabilization of plasmas,3 as well as plasma heating.

Properties of the toroidal momentum diffusivity (χϕ) and the convection velocity (V conv) in JT-60U H-mode plasmas have been obtained by plasma parameter scans such as the plasma current, neutral beam heating power and electron density. The toroidal momentum diffusivity increases with increasing heat diffusivity (χi) over a wide range of radii (r/a = 0.2–0.6) and χϕ/χi ∼ 0.7–3 at the half radius (r/a = 0.5). The inward convection velocity (−V conv) increases with increasing χϕ, and −V conv/χϕ ∼ 0.5–2 (m−1) at r/a = 0.5. It is found that the ratio χϕ/χi increases with increasing ion temperature and decreases with increasing electron density. These tendencies are observed in other radial positions of r/a = 0.3, 0.4 and 0.6. Moreover, the ratio −V conv/χϕ at r/a = 0.4, 0.5 and 0.6 increases with increasing ion and electron temperatures or temperature gradients.

The roles of momentum transport on the toroidal rotation velocity (Vt) profile and the properties of transport coefficients are found by transient momentum transport analysis. The perturbation technique enables us to evaluate the momentum diffusivity (χφ) and the convection velocity (Vconv), and to calculate Vt profiles driven by external torque input by neutral beams (NBs). The measured Vt profiles with and without the external torque input are almost reproduced by χφ and Vconv in low-β (βN < 0.4) plasmas. At higher β, the local pressure gradient plays a role in determining the local value of intrinsic rotation velocity. Concerning the momentum transport, χφ increases with increasing heating power, and decreases with increasing plasma current (Ip). In H-mode plasmas, χφ is smaller than that in L-mode plasmas under similar experimental conditions. It is found that χφ, which is separated from the non-diffusive term increases with increasing heat diffusivity (χi), χφ/χi ∼ 1-3, and -Vconv increases with increasing χφ, Vconv/χφ ∼ -2.5 to -0.7 m-1 , in H-mode plasmas.

Key parts of the ITER scenarios are determined by the capability of the proposed poloidal field (PF) coil set. They include the plasma breakdown at low loop voltage, the current rise phase, the performance during the flat top (FT) phase and a ramp down of the plasma. The ITER discharge evolution has been verified in dedicated experiments. New data are obtained from C-Mod, ASDEX Upgrade, DIII-D, JT-60U and JET. Results show that breakdown for E axis < 0.23–0.33 V m−1 is possible unassisted (ohmic) for large devices like JET and attainable in devices with a capability of using ECRH assist. For the current ramp up, good control of the plasma inductance is obtained using a full bore plasma shape with early X-point formation. This allows optimization of the flux usage from the PF set. Additional heating keeps l i(3) < 0.85 during the ramp up to q 95 = 3. A rise phase with an H-mode transition is capable of achieving l i(3) < 0.7 at the start of the FT. Operation of the H-mode reference scenario at q 95 ∼ 3 and the hybrid scenario at q 95 = 4–4.5 during the FT phase is documented, providing data for the l i (3) evolution after the H-mode transition and the l i (3) evolution after a back-transition to L-mode. During the ITER ramp down it is important to remain diverted and to reduce the elongation. The inductance could be kept ⩽1.2 during the first half of the current decay, using a slow I p ramp down, but still consuming flux from the transformer. Alternatively, the discharges can be kept in H-mode during most of the ramp down, requiring significant amounts of additional heating.