ELECTRON CYCLOTRON SYSTEM FOR KSTAR US-Korea Workshop Opportunities for Expanded Fusion Science and Technology Collaborations with the KSTAR Project Presented by Richard Callis General Atomics May 19, 2004

ELECTRON CYCLOTRON HEATING IS AN IMPORTANT TOOL FOR ADVANCED TOKAMAK RESEARCH Effective source of highly localized and controlled heating and current drive –Plasma heating

Effective source of highly localized and controlled heating and current drive –Plasma heating –Current profile control and sustainment ELECTRON CYCLOTRON HEATING IS AN IMPORTANT TOOL FOR ADVANCED TOKAMAK RESEARCH

Effective source of highly localized and controlled heating and current drive –Plasma heating –Current profile control and sustainment –Control of MHD instabilities ELECTRON CYCLOTRON HEATING IS AN IMPORTANT TOOL FOR ADVANCED TOKAMAK RESEARCH

Effective source of highly localized and controlled heating and current drive –Plasma heating –Current profile control and sustainment –Control of MHD instabilities Coupling of power to the wave is easy –Wave propagates in vacuum, remote antennas, insensitivity to plasma edge ELECTRON CYCLOTRON HEATING IS AN IMPORTANT TOOL FOR TOKAMAK RESEARCH

Effective source of highly localized and controlled heating and current drive –Plasma heating –Current profile control and sustainment –Control of MHD instabilities Coupling of power to the wave is easy –Wave propagates in vacuum, remote antennas, insensitivity to plasma edge Power density can be very high (~10 9 W/m 2 ) ELECTRON CYCLOTRON HEATING IS AN IMPORTANT TOOL FOR ADVANCED TOKAMAK RESEARCH

THE ABILITY TO MODIFY THE CURRENT DENSITY PROFILE IN A HIGH  PLASMA HAS BEEN DEMONSTRATED Increased negative central shear leads to increased core confinement f NI > 85% with nearly stationary profiles Off-axis co-ECCD increases negative central shear

NEGATIVE CENTRAL SHEAR SUPPORTS FORMATION OF INTERNAL TRANSPORT BARRIERS

PINPOINT LOCALIZATION OF EC POWER SUPPORTS STABILIZATION OF MHD MODES Stabilization of neoclassical tearing modes uses ECCD inside magnetic islands –Leads to higher  operation –Avoids plasma disruptions (2/1 modes) Accurate placement of ECCD is required to hit island –Real time feedback schemes developed Interaction of wave with instability allows measurement of mode onset conditions and growth rates for comparison to theory

ACTIVE TRACKING OF RATIONAL SURFACE MAINTAINS BENEFITS OF STABILIZING THE 3/2 NTM m=3/n=2 NTM suppressed by ECCD using feedback to optimize the location After mode disappears active tracking keeps ECCD on q = 3/2 surface  N can be raised above the onset condition even in the presence of sawteeth and ELMs

THE PROPOSAL IS FOR THE US TO PROVIDE KSTAR WITH A TURN-KEY 4 MW 170 GHz EC SYSTEM BY 2010 Four 1 MW 170 GHz gyrotrons identical to those developed for ITER Each gyrotron will use an IGBT solid state modulator, also an ITER design The transmission line will use evacuated waveguide components identical to that used on ITER The Antenna will be custom designed for KSTAR but adapted from the remote steering concept being used by ITER for the upper ports. An alternate design based upon the ITER midplane antenna will be evaluated prior to the start of detailed design.

THE GYROTRON SYSTEM WILL BE BASED UPON THE DEMONSTRATED HARDWARE BUILT FOR DIII-D AND ITER

THE GYROTRON POWER SUPPLY IS ALL SOLID STATE BASED UPON THE PROPOSED ITER POWER SUPPLY CONFIGURATION Single large transformer rectify feeding individual power supplies Power supplies are IGBT based Pulse Width Modulation design Gyrotron is protected from spark-down by a fast IGBT opening switch

THE EC TRANSMISSION LINE WILL BE ASSEMBLED FROM THE SAME COMPONENTS APPLICABLE TO ITER

THE LONG PULSE LAUNCHER WILL BE BASED UPON THE ITER REMOTE STEERABLE LAUNCHER CONCEPT The launcher uses a square corrugated waveguide of a length such that the exit beam mimics the input beam. Steering mirrors are located outside the vacuum vessel far from plasma disruption and heat loads. Scanning is limited to ±10° in all directions A fixed mirror at the plasma end of the square waveguide points the beam in the nominal direction Circular waveguide CVD window Fixed mirror Square waveguide ± 10°

A TURNKEY 4 MW 170 GHz ECH SYSTEM FOR KSTAR WOULD COST $19 M Prices are in $2004 Cost savings are assumed, because hardware is identical to ITER EC hardware and could be built at the same time, so quantity discount maybe applicable. Design and documentation is for KSTAR specific issues only, ITER covers major R&D costs. Installation supervision only, KSTAR is to cover cost of installation labor

FOR THE GYROTRON SYSTEM THE MAIN COST IS WITH THE GYROTRONS AND SUPERCONDUCTING MAGNET

THE 4 MW ELECTRON CYCLOTRON SYSTEM FOR KSTAR COULD BE READY FOR EXPERIMENTS BY 2010

SUMMARY Steady State Advanced Tokamak plasma research on KSTAR could be advanced by five or more years if the US contributed to a 4 MW EC system based upon the ITER design. The EC technology intended for ITER will receive real hands on testing, years before needed for ITER, allowing for improvements to reliability and performance. The cost (in 2004 $) would be ≈$19M, but could be lowered if Korea could support some of the costs, such as gyrotrons and power supplies.