ITER

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Scenario Integration and Control
in the BP Regime
ITER will achieve its initial burning plasma operation using a plasma operation scenario and plasma control methods that derive for the scenarios and methods used in present tokamaks. Feedback techniques will be used to precisely control the magnetic evolution of the plasma discharge, from initial plasma breakdown to final rampdown of the plasma current — without disruption — after controlled shutdown of the fusion burn. Feedback control of the plasma density and control of the applied heating auxiliary power during the current flattop will allow attainment of H-mode confinement and a constant-power DT fusion 'burn' with a predetermined power level. A combination of feedback-enabled fuelling rate control, auxiliary power control and boundary impurity injection control — provided to control divertor radiation — will allow fusion power and divertor power (power reaching the divertor targets) to be independently controlled. The achievement of simultaneous fusion power (burn) and divertor power control — needed for a reactor and necessary for ITER operation for subsequent burning plasma science study purposes — will constitute a first-of-kind demonstration of tokamak control in the 'reactor regime.


Physics Basis Integration and Validation
The 'reference' ELMy H-mode plasma operation scenario envisioned for ITER is built upon a combination of physics basis 'elements' — H-mode confinement, radiative divertor power and particle exhaust and MHD stable operation at 15 MA current and 3% volume-average beta — that present understanding of tokamak physics projects to be separately achievable. Attainment and control of a 500-MW, 400-s fusion burn will demonstrate that these physics basis elements can be achieved simultaneously and sustained in an integrated manner when the majority of the plasma heating comes from alpha particles and where the plasma temperature, ion and impurity densities and current profiles all reach essentially stationary conditions. Achievement of sustained and well-controlled fusion burn will constitute a first-of-kind validation of the science and technology basis for the achievement and control of reactor-relevant plasma operation.



ITER plasma operation will combine precise control of the plasma magnetic
configuration with closed-loop feedback control of the fusion power and
divertor power during the inductively-sustained fusion burn phase
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The ITER commissioning and plasma operation development provides for up
to 2000 machine pulses each year. High-duty factor and long-pulse development will support science studies and neutron irradiation testing to significant fluences
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Margin, Flexibility and Science and Technology Study Capabilities
The ITER reference operation scenario is designed to allow attainment of Q = 10 with modest reserve in critical physics and device operation capabilities, and hence it will be possible to vary scenario and plasma operation parameters whilst still maintaining 'burning plasma conditions'. This ability to carry out plasma parameter variation studies — 'parameter scans' in the parlance of the present fusion science program — makes ITER a fusion science facility capable of conducting detailed scientific studies of plasma behavior in the self-heating-dominated 'reactor regime'. This parametric flexibility of operation will be complemented by ITER's second important operational attribute: ability to conduct thousands of full-power, full-duration fusion power pulses during each year of operation. The 'reference' ITER operation plan allows for up to 18,000 pulses total and the equivalent of 12,000 500-MW, 440-s pulses over a ten-year period. This plan will provide ~0.1 MWa/m2 of first-wall neutron fluence — sufficient to conduct meaningful fusion materials testing — plus opportunities to conduct a systematic program of 'integrated' fusion science studies with 'reactor-like plasmas' in both inductively and non-inductively sustained operation regimes. See Experimental Opportunities (link) for more details on what can be done.

The ITER commissioning and plasma operation development plan
allows for up to 18,000 pulses and 12,000 full-performance equivalent
pulses over a 10-year period
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Advanced Tokamak and Steady-State Operation
ITER will be capable of plasma operation based upon 'advanced tokamak' (AT) modes, wherein improved plasma energy confinement (H-factor) and MHD stable operation at higher current-normalized-beta (beta-N) will allow attainment of burning plasma conditions where the reduced plasma current required (~10 MA) can be wholly sustained by a combination of plasma-pressure-driven bootstrap current and non-inductive radio-frequency and neutral-beam-injection current drive. Such AT operation has the potential for realizing steady-state reactor tokamak operation, and ITER is the only presently-envisioned burning plasma facility that will combine the steady-state magnets and steady-state first-wall and plasma-facing-component cooling required to fully realize steady-state operation. A flexible complement of heating and current drive systems, excellent plasma diagnostic coverage, provisions for implementation of real time control and the lack of hardware-imposed constraints on pulse number and integrated burn duration will make ITER an absolutely unique first-of-kind facility for confronting the challenges now foreseen for realizing steady-state AT operation in the burning plasma regime.

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