Status and update on indigenous mismatch transmission line (MMTL) system for ICH and CD test bed

ITER-India is responsible for delivery of 8+1 (prototype) RF sources to ITER. Each RF source will provide 2.5 MW of RF power at 2 VSWR in the frequency range of 35 to 65 MHz with other stringent specifications. Eight such RF sources will generate total 20 MW of RF power. Prior to development of prototype RF source, an R and D program has been launched using Diacrode and tetrode technologies to qualify final stage tube along with other critical components. In the R and D phase, single chain experimentation is being conducted at 1.5 MW/CW/2VSWR and 1.7 MW/CW/1.5 VSWR with any phase of reflection coefficient. India is developing unique 3 MW test facility for testing RF sources with variable load (up to VSWR 3 at any phase angle in between 0-360 degree), consisting of high power 50 Ohm dummy load, phase-shifter and stub. The combined assembly of phase shifter and stub is called MisMatch Transmission Line (MMTL) system. Stub will generate VSWR 1.0 to 3.0 and phase shifter will provide required phase angle for any frequency between 35 to 65 MHz. Detailed RF and thermal simulation of the MMTL system has been done using CST Studio and ANSYS. Calculation is done to optimize the length of stub and phase-shifter for the entire frequency band 35 - 65 MHz across which ICRF test bed will be tested. The mechanical design has been done accordingly and mechanical fabrication has been done with help of nearby professional industries. Thermal simulation shows that maximum temperature of inner and outer conductor may reach up to 85 degree C and 45 degree C respectively, along with active cooling. A detailed design and initial test results of MMTL system considering RF and mechanical aspect for testing ITER ICRF sources will be described in this paper. (author)