Garching,June 24 th, 2003F. Durodié LPP-ERM/KMS – CCFW Comments on the Report on Internal Matching for ITER Garching 24 June 2003

Garching,June 24 th, 2003F. Durodié LPP-ERM/KMS – CCFW Comments on Report NTT (CEA) Disruption Forces (missing !) –The In-vessel matching proposal uses capacitors with massive copper electrodes which are factors larger than those for JET : Length : 200mm / 75mm= 2.67 Radius : 145mm / 61mm= 2.38 Thickness : 6mm / 1.5mm= 4 –The loads induced have a strong parametric dependence on those dimensions. –E.g. the radial torque on the variable electrodes will in the end be restrained by the vacuum window : JET : 5 kNm ITER : 475 kNm ? (JET x 95) –The mitigation of disruption forces is one of the main causes for the delays on the ITER-like ICRF launcher : –strong recommendation to include a consistent picture of those forces into the design very early on !

Garching,June 24 th, 2003F. Durodié LPP-ERM/KMS – CCFW Comparison of the EM load Conditions for In-Vessel Matching Capacitors in JET, TS and ITER Magnetic ParametersTSJETITERCapacitor ParametersTSJETITER B T [T] ? Length of electrode cylinders L [mm]  t B v [T/s] ? Thickness of electrode cylinders d [mm]  t B r [T/s] ? Radius of outermost fixed electr. cyl. R e [mm] Dia. of base of fixed electrode [mm] D (nominal) TSJETITERJET/TSITER/JET Radial Torque on the electrodes M r  L. R e 3. B T.  t B v. d [mm 4 T 2 s -1 ] 1.4e99.2e9878e Vertical Torque on Electr. Cylinders M y,cyl  L. R e 3. B T.  t B r. d [mm 4 T 2 s -1 ] 0.35e96.1e9219e Vertical Torque on Electr. Base (*) M y,base  D 4. B T.  t B r. (f r / ) [A.U.] …2.4… Stress on brazed joint from M y,base   M y,base / D 2 [A.U.] 39153…3.9… (*) (f r / ) already takes into account the fact that on JET SS partially replaces Cu as well as the effect of the inductance.

Garching,June 24 th, 2003F. Durodié LPP-ERM/KMS – CCFW Comments on Report NTT (CEA) Electrical Circuit –Electrode cylinder 200mm : Equiv. to increased feeder length by 200mm : + 4kV Effect on Internal voltage of the capacitor –Voltage enhancement factor of 1.33 at 47.5 MHz (160 pF) and not 1.1 as erroneously mentioned in the report and further neglected. Ceramic 200mm ? –Losses on COMET ceramic is estimated at 300W. How does that compare with the proposed ITER capacitor and what are the thermal aspects ? –Bridge : CEA issued strong comments on the JET ITER-like antenna design concerning the geometry of the bridge/VTL and the excitation of non- TEM modes. –Circumference : ITER/JET = 1.6m/0.85m –Depth : 200mm + compressed length of bellows 200mm? = 400mm –Strong driver of non-TEM modes due to phase opposition of currents What is the effect on the matching and voltage/current balances ? Circuit model end of feeder Real end of feeder

Garching,June 24 th, 2003F. Durodié LPP-ERM/KMS – CCFW In-Vessel Matching Option Components Capacitor –Need for sliding contacts : Out-gassing in capacitor private vacuum cfr contact test for JET Need for separate pumping of capacitor ? Actuator –In order to obtain the required precision for JET (< 0.1mm) ENEA has designed and prototyped a hydraulic actuator : Requires position measurement near capacitor High Pressure bars. A present not compatible with water : viscosity > 20 cSt. Vacuum Window –RW / AK design Present understanding is that this type of design cannot easily been done for other impedances strongly different from 30 Ohm. For low impedance windows (6 Ohm) is the ceramic is operating in a lower electric field even when in a matched section ? –Torques induced by disruptions –As in JET may need to route services to capacitor Cooling / Hydraulic / Electric Need for Service stub in circuit ?