Activity name

Divertor and scrape-off layer physics, plasma-wall interactions

Activity type

Research

Objectives

•Participate in developing and validating physics for the plasma divertor for ITER on the basis of experimental, theoretical, and modeling results.
•Develop a quantitative understanding of heat loads on all plasma-facing components for steady state and transient plasma loads.
•Understand the role and effects of radiofrequency heating and magnetic perturbations on the scrape-off layer.
•Characterise and understand the multiple paths to hydrogen retention in plasma-facing components and the reliance on material and operating scenarios. Address the effects of mixed materials on material properties (e.g. erosion and thermal conductivity) and techniques for removing tritium.
•Develop new diagnostics for dust, erosion, and hydrogen retention and other processes.
•Develop methods to condition first wall components prior to operational campaigns and during campaigns (particularly for fuel recovery).

Term

2012-2017

Total budget for the term

NA

Key findings, lessons learned

1) Found a new empirical law for variation of peak heat flux on tokamak divertor target plates and a theoretical model to explain it which will enable more precise predictions for the ITER burning plasma.
2) Developed a new empirical law for variation of heat flux on tokamak inner main wall during start-up and ramp down of plasma current. These results led to a re-design of the ITER inner wall first panel shape.
3) Developed a new empirical law for the peak divertor target heat flux during plasma transient bursts (edge localized instabilities) which opens up new possibility that ITER could operate at higher plasma current before needing mitigation techniques to reduce the transients.
4) Demonstrated feasible wall conditioning schemes using low temperature plasmas generated with radio frequency waves which may also be used to recover wall trapped tritium fuel in ITER.
5) Improved understanding of tungsten melting under transient heat pulses which have provided key physics input to the design of the ITER divertor targets.
6) Improved understanding and modelling of likely material migration pathways and deposit formations/fuel retention during ITER burning plasmas.
7) Developed greater understanding and control of steady state divertor target heat load reduction using injection of impurities to enhance detachment of plasma contact with material targets

Activity name

Integrated operational scenarios

Activity type

Research

Objectives

Develop and establish operation scenarios, especially those foreseen in ITER, with emphasis on:
•Safe and reliable plasma break-down, current ramp-up, current ramp-down and plasma termination.
•Safe and reliable sustainment of the current flat-top, with identification of operational boundaries and performance.
•Identify and evaluate the capabilities of actuators – heating and current drive, fuelling, particle exhaust, (seed) impurity control and angular momentum injection – for achieving identified scenarios.
•Assess development of integrated plasma control procedures, especially for achieving steady-state operation in ITER and future burning plasmas (e.g. demonstration of burn control), with emphasis on real time control.
•Evaluate and propose suggestions for plasma development in ITER with emphasis on the consistency between plasma / scenario development program and hardware status for each phase of machine operation.
•Promote integrated modelling activities for ITER scenarios, with emphasis on validating the available scenario modelling codes and exploring the operational boundaries for the proposed scenarios for achieving ITER's goals.

Term

2012-2017

Total budget for the term

NA

Key findings, lessons learned

1) Developed methods to control the power fluxes on the divertor targets.
2) Integrated magnetic and kinetic control of scenarios for advanced tokamak configurations.
3) Demonstrated the use of lower hybrid waves at densities relevant to ITER operations.
4) Identified the plasma density levels for ITER baseline operations.
5) Examined plasma breakdown with radio frequency waves.
6) Developed advanced scenarios to improve plasma confinement in ITER.
7) Developed a dimensionless scaling for disruption scenarios.
8) Improved understanding of stability and performance of ITER steady-state scenarios.
9) Quantified the influence of gas injection methods on the coupling of radio frequency waves to the plasma.
10) Initiated experiments on achievement of high confinement mode in helium plasma in support of ITER operation.

1) Methods for divertor heat flux control
2) Integrated magnetic and kinetic control of advanced tokamak scenarios
3) Use of Lower Hybrid waves at ITER relevant densities
4) Demonstrating ITER baseline operation at q95 = 3
5) Plasma breakdown with EC waves
6) Development of advanced inductive scenarios for ITER
7) Dimensionless scaling of transport in advanced inductive scenarios
8) Stability and performance of ITER steady-state scenarios with ITBs
9) ICRF antenna performance with gas injection
10) Initiation of H-mode experiments in helium

Activity name

MHD, disruptions and control

Activity type

Research

Objectives

•Examine limits on plasma parameters (including instabilities) in both conventional and advanced tokamak devices.
•Control magnetic-hydrodynamic (MHD) instabilities via pressure and current profile control.
•Control MHD instabilities via conducting structures and additional coils.
•Study the interaction of MHD modes with plasma rotation, error fields and ripple.
•Define diagnostic issues related to measurement and control of instabilities.
•Characterise disruption and project implications for future machines.
•Validate theoretical models used in disruption studies, namely disruption prediction, avoidance and mitigation.
•Extend the existing disruption database.
•Develop tools and recommendations to predict disruption, avoidance, and mitigation.
•Assess disruption mitigation through pellets, strong gas puffs, and other techniques.
•Avoid and mitigate runaway electron production during plasma current decay.
•Develop scenarios of emergency plasma termination (fast shut-down).
•Identify diagnostic issues to predict, avoid, and mitigate disruptions.
•Develop plasma scenario and machine sequencing requirements for plasma target parameters and to avoid disruption.
•Gather feedback and control of plasma current, position and shape.
•Identify, control and reduce error fields.
•Validate experiments and theoretical models used for magnetic control simulations.
•Identify diagnostic issues related to magnetic control.
•Develop, test and make recommendations on magnetic control using the plasma control simulator.

Term

2012-2016

Total budget for the term

NA

Key findings, lessons learned

1) Specified heat loads resulting from radiation flashes from mitigated disruptions.
2) Specified the delay and prediction warning times for the ITER disuption mitigation sytem (DMS).
3) Identified the required quantities of gas and species for the ITER DMS.
4) Validated disruption timescales, refinements in disruption, predictions and avoidance for ITER.
5) Validated the feasibility of runaway electrons in the ITER DMS.
6) Demonstrated sawtooth control using power and heating on several devices.
7) Controlled plasma instabilities in real time using steering of radio frequency waves into the plasma.
8) Examined thresholds for resistive magnetohydrodynamic instabilities (stability, rotation sheer) by comparing machines with differing aspect ratios.
9) Confirmed that the empirical error field correction (n=1) is consistent with minimising the resonant harmonics of the total external error field.
10) Model predictions show that magnetic perturbations introduced by fields applied for edge localized mode instability control will be less than ±1.75% of the minor radius of the baseline for the heating mode and the boundary displacement resulting from core MHD instabilities in ITER is predicted to be less than ±1.5% of the minor radius.

Activity name

Transport and confinement

Activity type

Research

Objectives

•Maintain confinement databases and enhance or increase as necessary.
•Develop an improved characterisation of the L-H transition threshold.
•Determine characteristics for confinement of tokamaks worldwide.
•Develop an improved characterisation of particle and impurity transport.
•Determine electron thermal transport properties over a range of conditions.
•Determine ion thermal transport properties over a range of conditions.
•Improve characterisation and understanding of momentum transport and plasma rotation.
•Improve characterisation and understanding of barrier formation.
•Validate models.

Term

2012-2017

Total budget for the term

NA

Key findings, lessons learned

1) Developed an improved formulation for the prediction of deuterium-tritium transport in ITER and characterised the role of transport sources versus core sources.
2) Developed an improved formulation to predict tungsten transport in ITER demonstrating the importance plasma rotation and peaking of the density profile and showing that the situation will be favourable in ITER.
3) Identified the role of fast particles in improving plasma core transport and pedestal stability in ITER.
4) Demonstrated plasma fuelling with pellets to compensate for the particle transport induced by the application of magnetic perturbation fields for control of edge localized transient plasma instabilties .
5) Demonstrated the existence of a new high confinement regime on multiple devices (no edge particle transport barrier and absence of edge localized transient instabilities) and characterised the operational space.

Activity name

Pedestal and edge physics

Activity type

Research

Objectives

Improve understanding of:
•The mechanism for transition to the high confinement mode and the edge pedestal structure, including the impact of external controls.
•The origin, dynamics and control of edge localized plasma instabilities, including the conditions for access to regimes in which these instabilities are naturally small and the extrapolability of these regimes to ITER.
•The interplay between the plasma core, the edge pedestal region and the plasma layer in contact with material surfaces.
•Identify internally consistent solutions for the ITER pedestal.
•Operating regimes for ITER with pedestal properties compatible with the required core confinement and power and particle exhaust requirements.

Term

2012-2017

Total budget for the term

NA

Key findings, lessons learned

1) Validated the principal model to predict pedestal pressure.
2) Demonstrated edge plasma instability control using (resonant) magnetic field perturbations in multiple machines.
3) Gained understanding of the reduced performance of the pedestal in tokamaks using tungsten plasma-facing armour fusion as due to the misalignment of plasma density and temperature profiles.
4) Demonstrated edge plasma instability control using fuel pellet injection in multiple machines and development of a formulation to explain the mechanism through nonlinear magnetohydrodynamic simulations.
5) Developed a naturally edge plasma instability-free plasma regime in multiple devices and established an experimental threshold for the transition to higher plasma confinement in this mode of operation.

Activity name

Energetic particle physics

Activity type

Research

Objectives

Influence on destabilisation of magnetosonic waves and energetic particle modes of:
•Asymmetric magnetic fields on fast particle losses.
•Interaction of fast ions and magnetohydrodynamic instabilities.
•Injection of neutral atoms for plasma heating and plasma current drive.

Term

2012-2017

Total budget for the term

NA

Key findings, lessons learned

1) Examined fast ion loss and redistribution due to destabilization by localized magnetosonic waves.
2) Determined the impact (physics understanding) of localised radio frequency heating on localized magneticsonic waves.
3) Quantified fast ion losses due to asymmetric magnetic fields applied for control of edge plasma instabilities.
4) Refined the predictions of fast ion power loads in ITER.
5) Established transitions from steady-state saturated plasma instabilities to nonlinear evolution.

Activity name

Diagnostics

Activity type

Research

Objectives

•Identify specific measurement requirements for machine protection, control, evaluation and understanding of burning plasma experiments in ITER.
•Advise the ITER Organization on the selection and design of diagnostic techniques.
•Participate in the assessment and review of system designs as requested by the ITER Organization.
•Develop and maintain the International Diagnostics Database (IDD).
•Propose design and testing of new concepts for diagnostic systems and components for possible application on ITER and reactor grade devices that will follow ITER.
•Establish and manage Specialists Working Groups which work mainly in the electronic domain on the topics of the Diagnostics Topical Group.

Term

2012-2017

Total budget for the term

NA

Key findings, lessons learned

1) Developed a road map for first mirror survival (including a consistent strategy and process) and reviewed several example proposals and prototypes.
2) Demonstrated successful mirror cleaning in labs.
3) Tested new techniques for measurement of dust in tokamaks.
4) Tested lost alpha detectors based on germanium and developed alternative options.
5) Developed models for estimates of stray light (mm to visible) and detection options for stray radio frequency waves.
6) Updated proposals for ITER measurement requirements.