tore supra association euratom-cea 1 b.beaumont / chengdu / 21.10.06steady state rf systems...

TORE SUPRAAssociationEuratom-CEA

1B.Beaumont / Chengdu / 21.10.06 Steady State RF Systems

Presented by B.Beaumont

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



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.



Outline

A selection of recent Tore Supra experimental resultsSystem integrationRF techniques developments and R&D

LHCD power upgrade,ITER-like ICRH antennaAntenna studiesExample of RF design for ITER : in-port matching ICRH

antenna

Conclusion



Outline



antenna

Conclusion



Tore Supra Exp. Results

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, '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

2001- the 20th IAEA

After the 20th IAEA

8 M

W

2 MW



ICRH+LHCD Multi-MW

PICRH

PLH

Ptot

MW

Ip (MA)

Stored energy(MJ)

Te(0)

Ti, @r/a=0.2

keV

Line density(1019m-2)

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

shot 33612, Combination of ICRH (57 MHz - 8.5 MW) and LHCD (3.7 GHz -1.4 MW).(R=2.4m, a=0.72m, Ip= 0.9MA, BT=3.7T)



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 n & q theory. Large peaking of heat fluxes:- governing the temperature and the coupled power- inducing shear stress in the components -> CFC !



Outline



antenna

Conclusion



System integrationSuccessful operation of RF systems depends on integration in Tokamak system :

Arc protection / RF diagnostics / matchingreliabilitydiscrimination (cross-talk)Response time

Power controls Current balance controlArray phase control Power Ramp-up balanceRT control loops (internal and external to RF syst.)

Recovery after trip : strategy (reduced power, counters, …)on/off solid state switch

Degraded mode of operationpart of antenna missing => Stresses=> power limitmaintenance schemes

Long process :

Trial and errors

Water leaks…

Breakdowns…

Improvements

Time…



Outline



antenna

Conclusion



RF developmentsTore Supra is exploring long duration plasmas

Plasma size (a~0.7m) : need for non inductive CDLarge operational domain = large powerLarge power = appropriate PFC and controls

Highest efficiency for volume CD is LHCD

On going upgrade of LHCD system to 8MW:New LHCD launcherNew high power CW klystron

ITER support :New TS LHCD launcher is ITER-like DesignITER-like ICRH antenna



Outline



antenna

Conclusion



LHCD upgradeHigh 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)

500 kW CW Mock up

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



LHCD upgradePassive/Active Multijunction Launcher:

Large cooling efficiency

Target n//= 1.72 +/- 0.28 @ +/- 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

Copper

1.82 mm



Outline



antenna

Conclusion



ITER like ICRH Antenna

•First experiments in 2003 •Faraday shield modified to reduce coupling•Experiments in end 2006/2007 with improved current control loops

Xc1

Xc2

Rs

Xs

Rs

Xs

Ia

I2

I1

Va

Xs

Xs

Xc3

Rs

Rs

Xc4I4

Vb

I3

Ib

kt

kt

kpkp

Ifeed

R

0

Rin+jXin

Rin+jXin

jXc1

jXc2

I1

I2

Conventional

Conjugate-T concept = ITER Relevance : ELM Resilient Antenna



Outline



antenna

Conclusion



Antenna Studies

Studies of RF components :PAM launcher for JETPAM launcher for ITEREast ICRF AntennaITER ICRF antenna…

TE10-TE30 Mode Converter

3 dB coupler

PAM

RF loads

JET PAM Launcher features 300 waveguides showing the mechanical structure which holds the wave guide array from the back flange

The ITER array is based on the PAM concept for its cooling capabilities. More than 1000 waveguides facing the plasma.

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



Outline



antenna

Conclusion



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

Rear partFront part

Interface (vacuum tight) between front and rear parts

Modular construction

Shielding in front part

Remote RF windows

Every component is water cooled

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 assembliesExample of mechanical study : disruption




• Internal components :

• Front part : static structure, vacuum tight

• Rear part : adjustable impedance, private vacuum

• Compact in port design, integrated matching

RF windows

Central conductor

RF input

Central conductor detailed

Outer conductor

Driving mechanisms, cooling



Outline



antenna

Conclusion



Conclusion• Significant progress of injected RF power has been obtainedin 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



EpilogueIt 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

tore supra association euratom-cea 1 b.beaumont / chengdu / 21.10.06steady state rf systems...

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