CCFW32 – 25th July 2002 – JET F. Durodié LPP-ERM/KMS 1

Work program for Validation of External Matching for The ITER-ICRF System

F. DurodiéCCFW32, 25 July 02, Culham (JET)

• Motivation

• Work program FP5 and FP6

CCFW32 – 25th July 2002 – JET F. Durodié LPP-ERM/KMS 2

Motivation

• Concerns raised about the FDR ITER ICRF System

– High Voltages and Electric Fields in the Tuner stubs• 40 kV (DDD)

• Need for ceramic supports to keep tight spacing (15mm) (DDD)

– Need for High Current Sliding Contacts• 4 kA sliding over 1.3m in vacuum (DDD)

– Bandwidth• Initially the straps and feeders in the FDR design were too long to guarantee

operation above 55 MHz In the DDD the straps and feeders are shortened to 30cm (in the tables but not in the drawings) to recover the bandwidth.

– Overall Complexity

CCFW32 – 25th July 2002 – JET F. Durodié LPP-ERM/KMS 3

35 40 45 50 55 600

5

10

15

20

25

30

35

401st VTL 7.0 Ohm 0.150m 197 nH/m

Frequency [MHz]

Ant

enna

, F

eede

r an

d (V

)TL

volta

ges

[kV

]

35 40 45 50 55 600

5

10

15

20

25

30

351st window at 2.10 m (squares), 2nd window at 3.70 m (circles)

Frequency [MHz]

Vac

uum

Win

dow

vol

tage

s [k

V]

(--)

- c

urre

nts

[kA

(x

10)]

(.)

Ex-Vessel Matching• Shorter Straps 0.26m as in JET-EP

– Stack 3 RDL in height

– Power per RDL 1.7 MW

• Other Assumptions on Straps, Feeders and coupling as in DDD

FDR Tuners

A F BC

W(V)

W(I)

CCFW32 – 25th July 2002 – JET F. Durodié LPP-ERM/KMS 4

Motivation (2)

• Is there enough scientific grounds to justify complexity of the FDR in-vessel matching when there is another solution with lower electrical stress (30 kV vs. 40 kV) ?

• In its report to the CCE-FU of 9 Jul 2001, the FPC endorsed the recommendation of the AHG on the JET-EP Phase II devoted to the ICRH antenna design (June 7, 2001) to request all interested Associations and EFDA to develop a programme of design and R&D work for the further development of the ITER ICRF array design and technology using alternative internal concepts and external matching concepts

• Two Task Agreements are put in place to study alternatives to the FDR baseline design :

– An ITER relevant lumped capacitor

– An Ex-vessel matching concept/design

CCFW32 – 25th July 2002 – JET F. Durodié LPP-ERM/KMS 5

Work Program FP5 (till April 2003)

• Conceptual Design of Ex-Vessel Matching for ITER-FEAT– Identification of the Circuit + Electrical Analysis

• Select for compactness of tuning elements compatible with the overall requirements on electrical performance

– Identification/Specification of• Space Requirements – compatibility with fundamental ITER requirements (e.g.

cryostat, bioshield,…) and requirements appearing from the FDR that could be relaxed

• RF components to implement the circuit• The RF components that presently are not yet CW capable and the R&D required

for those components

– Input/Liaison with ITER required• Torus and RF sources buildings layout drawings• All other requirements specific to the area just outside the bio shield where the

ex-vessel matching components will be located

• JET-EP ITER-like ICRF antenna

CCFW32 – 25th July 2002 – JET F. Durodié LPP-ERM/KMS 6

Ex-Vessel Matching RF components• (Vacuum Window)

– The electrical stress is within the present day use on several experiments (< 30 kV).

– A design exists for a CW vacuum window (Kaye, Walton)– Document operational experience of the LHD CW vacuum window.

• Ex-Vessel Transmission Line components– Phase-shifters and Stubs

• Investigate what are the limits for “standard” (dry) components (e.g. Spinner…)• Investigate if “liquid” components (LHD) can be optimized for size

– The stub has successfully been tested CW to 46 kV at 50 MHz– The LHD phase-shifter has been redesigned new tests could take place April 2003

– Cooling and Losses• Document operational experience of the LHD cooled transmission line

components.

• Ex-Vessel Capacitors– May still be the most compact solution but other ELM resilient circuits not

requiring capacitors are emerging. (Goulding, Lamalle, Monakhov)

CCFW32 – 25th July 2002 – JET F. Durodié LPP-ERM/KMS 7

Work Program FP6 (2003-2006)• JET-EP ICRF Launcher : experimental confirmation of

– short strap design philosophy as a way to increase power density

– performance of the ELM resilient nature of the circuit with real ELMs and H-mode SOLs (stability of control of the antenna array)

– It appears to be possible to test an ITER relevant capacitor on the JET-EP antenna towards the end of the program :

• Remove present inner VTL and capacitors, replace the contacting flange on the feeder with the fixed electrode part of the “Open Capacitor or All-metal” capacitor, a plug-in inserted in the Outer-VTL caries the variable electrode, T-junction and Impedance transformer.

• Possibly size may limit operation to the upper frequencies (> 50 MHz), Disruption considerations may limit the plasma performance.

• BUT It may be an unique opportunity to validate an “open capacitor” facing an ELMing H-mode plasma

• Further detailed engineering and design of the RF components identified in the FP5 work program

– TBD as components and specifications become clear during FP5 : collaboration with industry (e.g. Spinner, …) or effort (e.g. the launcher) from association(s)

– follow-up of results obtained on the liquid filled transmission lines of LHD

CCFW32 – 25th July 2002 – JET F. Durodié LPP-ERM/KMS 8

Replace Inner VTL with plug-incarrying Variable electrodes,T-Junction and Transformer

Replace (bolted) finger contact withfixed electrodes on the feeder ends

CCFW32 – 25th July 2002 – JET F. Durodié LPP-ERM/KMS 9

Array Stability

• Control Algorithm Studies are starting :– (MatLab-Simulink)– Use full impedance matrix from ICANT

• Later more refined models from MWS are expected

– Will be able to use complex (amplitude, phase) power sources driving the array (now 0 and ).

– Can inject errors, noise (electric, mechanical), dead bands etc…

– First “look and feel” : touchy• Need to limit all sources to the one having the toughest conditions• Consequences for a large array ?

– Need to understand and control– Experimental verification on JET-EP

CCFW32 – 25th July 2002 – JET F. Durodié LPP-ERM/KMS 10

Array Stability

• Only toroidal coupling• No linkage between sources • Slightly different in starting

values of the capacitor• Can be solved by linking the

sources

0 1 2 3 4 5 60

0.5

1

1.5

2

2.5

3

3.5

4Vinc [kV]

simulation time [s]

P (

r) Q

(g)

R (

b) S

(m)

0 2 4 60

1

2

3<<Coupling>>

simulation time [s]

Rsc

ale