Preparing ITER ICRF : Test of the Load Resilient Matching Systems on an Antenna Mock-up

The reference design for the ICRF antenna of ITER is constituted by a tight array of 24 straps grouped in 8 triplets. The matching network must be load resilient for operation in ELMy discharges and must have wave spectrum control for heating or current drive operation. The load resilience is based on the use of either hybrid couplers or Conjugate-T circuits. However the mutual coupling between the triplets at the low expected loading strongly counteracts the load resilience and wave spectrum control. Using a mock-up of the ITER antenna array with adjustable water load matching solutions are designed and tested. We show that suitable decoupler circuits neutralize the mutual coupling effects and that the wave spectrum can be controlled by the anti-node voltage distribution. A matching solution using four 3dB hybrids and the wave spectrum feedback control by the decouplers provides outstanding performances if each pair of poloidal triplets undergoes a same load variation. The Conjugate-T solution is presently considered as a back-up option.