Heating and Current Drive Physics
ITER will utilize plasma heating and current drive (H/CD) systems to initiate, sustain and control the largely-self-heated fusion burn and to optimize the plasma current profile and sustain the plasma current during long-pulse/steady state 'advanced performance' operation. The present design calls for provision of 73 MW of H/CD power, to be apportioned among negative ion neutral beam injection (NBI), electron cyclotron rf (ECRF) and ion-cyclotron rf (ICRF) systems. The ITER tokamak and facility are configured to also support later addition of lower hybrid rf (LHRF) and/or upgrade of one or more of the three initially-installed systems to increase total power to 110 MW. Specifications are for power delivered to or coupled to the plasma.

System	NBI	ECRF	ICRF	LHRF
Energy or frequency	1 MeV	170 GHz	~50 MHz	5 GHz
Power (initial)	33 MW	20 MW	20 MW	---
Equatorial ports (initial)	2	1	1	---
Maximum power (not simultaneous, total 3/4 110 MW)	50 MW	40 MW	40 MW	20 MW

The 73 MW of initially-installed power provides substantial margin relative to the 50 MW of heating needed for nominal 500 MW Q = 10 operation, and the mix of NBI and two rf H/CD systems will provide the flexibility and H/CD power and localization control necessary to support heating through H-mode transition and on to sustained fusion burn; fusion burn (power) control; current drive and current profile control in steady state scenarios; and localized CD for control of MHD instabilities.

Selection Basis and ITER Opportunities
The selection basis for candidate ITER H/CD systems has received extensive community scrutiny, with both physics requirements and technology feasibility for implementation ITER being considered. The fundamental physics bases for heating and CD, status and results in present experiments, key aspects of application to ITER and technology developments required are detailed in ITER Physics Basis Chapter 6: Plasma auxiliary heating and current drive (Download PDF). The overall conclusion is that the fundamental physics and technology bases for each of the 4 candidate systems are well in hand and that open issues center either on questions of optimal physics application for ITER 'advanced performance' operation and/or questions of how the respectively technologies (beam and rf power sources, rf coupling and wave launching structures, etc.) can be realized in an ITER-class device. Details and discussion of challenges and opportunities for solution in present experiments and/or resolution in ITER will be found in the four system-specific links below. Here it suffices to say that the fundamental physics basis for each candidate system is well understood, viable technology options exist for the realization and reliable operation in ITER of all candidate systems and that corresponding opportunities for conducting definitive 'reactor-regime' science and technology validation studies exist. Furthermore, while the underlying basis for obtaining steady-state 'advanced performance' operation in ITER is still being clarified, it can be anticipated that the planned mix and magnitude of H/CD options will be critical to the conduct of definitive 'reactor-regime' explorations of this topic in ITER.

	Neutral Beam Injection
	Electron Cyclotron
	Ion Cyclotron
	Lower Hybrid
	H/CD Requirements and Options for Advanced Performance and Steady State Operation

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