1. Progress Towards RF Steady State Systems For Fusion Devices
A.Argouarch, B.Beaumont, G.Berger-By, P.Bibet, F.Bouquey, S.Brémond, C.Darbos, L.Delpech, , G.T.Hoang, F.Kazarian, M.Lennholm, R.Magne, L.Millon, P.Mollard, M.Prou, K.Vulliez and Tore Supra Team
Association Euratom-CEA, Centre de Cadarache,
13108 SAINT PAUL LEZ DURANCE, France
Presented by B.Beaumont

2. Introduction
RF systems are widely used on magnetically confined fusion experiments.
Developments during many years have produced RF systems which have supported the progress of plasma performance and opened up new areas of investigation.
For the next step devices, long pulse operation is essential and it is a new challenge for the integration of the RF systems. They have to be highly reliable, with built-in strategies to recover from trips and breakdowns.

3. Outline A selection of recent Tore Supra experimental results
System integration
RF techniques developments and R&D
LHCD power upgrade,
ITER-like ICRH antenna
Antenna studies
Example of RF design for ITER : in-port matching ICRH antenna
Conclusion

4. Outline A selection of recent Tore Supra experimental results
System integration
RF techniques developments and R&D
LHCD power upgrade,
ITER-like ICRH antenna
Antenna studies
Example of RF design for ITER : in-port matching ICRH antenna
Conclusion

5. Tore Supra Exp. Results After the 20th IAEA 8 MW 2001- the 20th IAEA
The progress in term of RF assisted discharges can be expressed in the domain Energy/Duration.
Recent experimental work is focused on :
Combined operation of RF systems : The high power & performance quest
Interaction studies : try to live together
Identify and study specific issues :
Heat : Private heat flux, local RF losses, heat flux from other antennas, limiter connections, Protons impacts… + for ITER : shadowing of blanket modules, a's contributions…, NB shine through…
Coupling : Plasma/antenna distance, location of fuelling, pellet injector, relative antenna radial positions,…
Local enhanced RF fields .. Even far from antennas

6. ICRH+LHCD Multi-MW MW
Ptot
PICRH
Simultaneous use of multi-frequencies RF heating/CD systems (ICRH, LHCD, ECH)
Power level in excess of 10 MW, mainly ICRH, during pulses lasting up to several tens of resistive times
9MW of ICRH coupled to plasma sustained by LHCD is safe condition required for continuous operation
4MW/one minute ICRH pulse in LHCD (3MW) plasmas
Line density
(1019m-2)
PLH
Ip (MA)
Stored energy
(MJ)
keV
Te(0)
shot 33612, Combination of ICRH (57 MHz MW)
and LHCD (3.7 GHz -1.4 MW).
(R=2.4m, a=0.72m, Ip= 0.9MA, BT=3.7T)

7. Safety Control loops
IR image of IC antenna, at t = 63.7s, in a combined ICRH (4MW)/LHCD (3MW) discharge
Various hot spots on the ICRH antennae are identified
1: sensitive to the total power
2: mixed total IC power and private IC power
3: sensitive to LH power only
4: predominantly private IC power
 input for RT Controls & Algorithms
Reality is far from the classical ln & lq theory. Large peaking of heat fluxes:
governing the temperature and the coupled power
inducing shear stress in the components -> CFC !

8. Outline A selection of recent Tore Supra experimental results
System integration
RF techniques developments and R&D
LHCD power upgrade,
ITER-like ICRH antenna
Antenna studies
Example of RF design for ITER : in-port matching ICRH antenna
Conclusion

9. System integration Long process : Trial and errors Water leaks…
Successful operation of RF systems depends on integration in Tokamak system :
Arc protection / RF diagnostics / matching
reliability
discrimination (cross-talk)
Response time
Power controls
Current balance control
Array phase control
Power Ramp-up balance
RT control loops (internal and external to RF syst.)
Recovery after trip :
strategy (reduced power, counters, …)
on/off solid state switch
Degraded mode of operation
part of antenna missing => Stresses=> power limit
maintenance schemes
Long process :
Trial and errors
Water leaks…
Breakdowns…
Improvements
Time…

10. Outline A selection of recent Tore Supra experimental results
System integration
RF techniques developments and R&D
LHCD power upgrade,
ITER-like ICRH antenna
Antenna studies
Example of RF design for ITER : in-port matching ICRH antenna
Conclusion

11. RF developments Tore Supra is exploring long duration plasmas
Plasma size (a~0.7m) : need for non inductive CD
Large operational domain = large power
Large power = appropriate PFC and controls
Highest efficiency for volume CD is LHCD
On going upgrade of LHCD system to 8MW:
New LHCD launcher
New high power CW klystron
ITER support :
New TS LHCD launcher is ITER-like Design
ITER-like ICRH antenna

12. Outline A selection of recent Tore Supra experimental results
System integration
RF techniques developments and R&D
LHCD power upgrade,
ITER-like ICRH antenna
Antenna studies
Example of RF design for ITER : in-port matching ICRH antenna
Conclusion

13. LHCD upgrade 500 kW CW Mock up Lessons from this R&D program:
High power CW klystron development with TED:
Target = 700 kW CW on VSWR=1.4 any phase (and 750 kW on matched load)
5 years effort nearing completion:
Large collector (~1600kW beam power)
2 windows output circuit +recomb. circuit
Diode type klystron
Prototype has delivered 700kW on load during several hours
problem on geometry assembly faulty brazing suspected (under investigation)
CIMES
Lessons from this R&D program:
Close collaboration with supplier essential
Intermediate tests to validate sub components and steps mandatory. Specific field => Dedicated test beds

14. LHCD upgrade Stainless steel Copper 1.82 mm
Passive/Active Multijunction Launcher:
Large cooling efficiency
Target n//= /- +/- 90°
CW power ~3MW at 25 MW/m²
200 waveguides in total, 16 RF inputs (windows)
3 years fabrication inc. Specific R&D
Lessons from this R&D program
Example of plug antenna (like all TS antennas)
Integration of many different components & contracts
Firms are very skilled…until they have to do the real thing
stop points on brazing, material procurement,…
Specific R&D performed on explosion bonding
Tests and samples essential (as usual)
Stainless steel
1.82 mm
Copper

15. Outline A selection of recent Tore Supra experimental results
System integration
RF techniques developments and R&D
LHCD power upgrade,
ITER-like ICRH antenna
Antenna studies
Example of RF design for ITER : in-port matching ICRH antenna
Conclusion

16. ITER like ICRH Antenna
Ifeed R0
Rin+jXin
jXc1
jXc2 I1 I2
Conventional
Conjugate-T concept = ITER Relevance : ELM Resilient Antenna
First experiments in 2003
Faraday shield modified to reduce coupling
Experiments in end 2006/2007 with improved current control loops X c1 c2 R s I a 2 1 V c3 c4 4 b 3 k t p

17. Outline A selection of recent Tore Supra experimental results
System integration
RF techniques developments and R&D
LHCD power upgrade,
ITER-like ICRH antenna
Antenna studies
Example of RF design for ITER : in-port matching ICRH antenna
Conclusion

18. Antenna Studies Studies of RF components : PAM launcher for JET
PAM launcher for ITER
East ICRF Antenna
ITER ICRF antenna …
JET PAM Launcher features 300 waveguides showing the mechanical structure which holds the wave guide array from the back flange
ITER LHCD launcher issues :
Efficient water cooling and neutron shielding
Antenna tip: erosion; low Z materials: brazing?
Technology options for antenna realisation:
technology based on uni-axial iso-static pressure
machining and electron beam welding
Materials: Glidcop or CuCrZr, Be facing plasma
The ITER array is based on the PAM concept for its cooling capabilities. More than 1000 waveguides facing the plasma.
TE10-TE30 Mode Converter
3 dB coupler
PAM
RF loads

19. Outline A selection of recent Tore Supra experimental results
System integration
RF techniques developments and R&D
LHCD power upgrade,
ITER-like ICRH antenna
Antenna studies
Example of RF design for ITER : in-port matching ICRH antenna
Conclusion

20. ITER- ICRH antenna proposal
Rear part
Front part
Interface (vacuum tight) between front and rear parts
Modular construction
Shielding in front part
Remote RF windows
Every component is water cooled
ICRH antenna is constituted of 2 parts
Front part which is under the machine vacuum and is supported by the front part of the antenna port plug
Rear part which is under a private vacuum isolated from the machine vacuum and is supported by the rear part of the antenna port plug

21. ITER- ICRH antenna proposal
ICRH antenna constituted of 6 modules all identical except the front face (Faraday screen + current straps) that has to shape the blanket modules and plasma
This design has been made with the constraint to be able to assemble/disassemble each of the components that constitute the antenna:
Commissioning
Tests
Repair
are possible on sub assemblies
Example of mechanical study : disruption

22. ITER- ICRH antenna proposal
Internal components :
Front part : static structure, vacuum tight
Rear part : adjustable impedance, private vacuum
Compact in port design, integrated matching
RF windows
RF input
Outer conductor
Central conductor
Driving mechanisms, cooling
Central conductor detailed

23. Outline A selection of recent Tore Supra experimental results
System integration
RF techniques developments and R&D
LHCD power upgrade,
ITER-like ICRH antenna
Antenna studies
Example of RF design for ITER : in-port matching ICRH antenna
Conclusion

24. Conclusion Significant progress of injected RF power has been obtained
in steady state operation in Tore Supra
On going studies on RF systems, incl. ITER, take into account integration aspects, key element for success:
Magnetic field lines connections (shadows, fuelling system, connection length…)
Interaction with other antennas, beams,…
Protections, RT control loops  Safe operation (Machine&RF)
Degraded modes of operation
Recovery from trips
Commissioning and conditioning
Readiness tests
BUT it could be a long process
Uncertainties on design parameters call for margins

25. Epilogue
It is not guaranteed that one has a fully operational system even though all bits and pieces described in the WBS are available:
Figueras, Spain, near Dali Museum