The Problems of RF Launchers in DEMO Environment and

Requirements to Address them

J.R. Wilson, R.J. Goldston, J.C. Hosea

ReNew Theme III Workshop

UCLA March 5, 2009

RF Wave Energy is used for a variety of purposes on present devices and is

proposed to be used on an AT DEMO to:

• Heat the plasma

• Control the Current Profile– Majority Bootstrap CD

• Control Plasma Rotation

• Control MHD Stability– NTM stabilization

Other concepts will have similar requirements

Challenge

• While there are some issues with wave propagation and absorption in the core plasma, a large class of challenges involve the launchers and their interaction with the scrape-off plasma

Issues possibly addressed on ITER• Power Density

– How much real estate is allowable?

• Delicate components close to plasma– ECH mirrors– LH waveguide vanes– ICH Faraday screen

• Power deposition in scrape off plasma– LH fast electrons– ICH SOL sheaths

• Unacceptable modification of pedestal

Hot spot in NSTX with open field line connection

Depends on antenna spectrum

Alcator C-Mod ICRF RF driven erosion on surfaces connected to open field lines

Ameliorated with Boronization – Not workable in DEMO?

Issues not addressed on ITER

• Launchers will operate at high temperature– New cooling techniques required

• Launchers will operate in a significant radiation environment

Will require new materials

ITER Solutions geared toward ITER Requirements

Need facility that’s allows for antenna development in the presence of challenging plasmas