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AbstractAn electron cyclotron resonance heating system is commissioned on Aditya tokamak to carry out pre-ionization, start-up, and heating experiments. A high-power microwave source (gyrotron), capable of delivering 200-kW cw power at 28 ± 0.1 GHz, is commissioned successfully using a water dummy load for pulsed operation. The output mode of the gyrotron is TE02. The output power of the gyrotron is measured using microwave probe couplers, a spectrum analyzer, and calorimetric techniques. A hardwired interlock operates a rail-gap-based crowbar system in less than 10 μs under fault condition and protects the gyrotron. The rail-gap crowbar operation has been qualified with the high-voltage power supply by performing a 10-J wire-burn test prior to energizing the gyrotron.A transmission line consisting of matching optic units, dc break, polarizer, miter bend, and corrugated waveguides terminates with a boron nitride window. The total attenuation in the line is measured to be less than 1.1 dB. Based on quasi-optical theory, a beam launcher is designed, fabricated, and tested for ultrahigh-vacuum compatibility prior to commissioning on tokamak.After successful operation of the gyrotron on the dummy load, the gyrotron output has been coupled to the ADITYA tokamak, and successful breakdown of neutral gas is observed without assistance from an ohmic transformer.

RF systems in the ion cyclotron resonance frequency (ICRF) range and electron cyclotron resonance frequency (ECRF) range are in an advanced stage of commissioning, to carry out pre-ionization, breakdown, heating and current drive experiments on the steady-state superconducting tokamak SST-1. Initially the 1.5?MW continuous wave ICRF system would be used to heat the SST-1 plasma to 1.0?keV during a pulse length of 1000?s. For different heating scenarios at 1.5 and 3.0?T, a wide band of operating frequencies (20-92?MHz) is required. To meet this requirement two CW 1.5?MW rf generators are being developed in-house. A pressurized as well as vacuum transmission line and launcher for the SST-1-ICRF system has been commissioned and tested successfully. A gyrotron for the 82.6?GHz ECRF system has been tested for a 200?kW/1000?s operation on a water dummy load with 17% duty cycle. High power tests of the transmission line have been carried out and the burn pattern at the exit of transmission line shows a gaussian nature. Launchers used to focus and steer the microwave beam in plasma volume are characterized by a low power microwave source and tested for UHV compatibility. Long pulse operation has been made feasible by actively cooling both the systems. In this paper detailed test results and the present status of both the systems are reported.

Abstract: An ion cyclotron resonance heating (ICRH) system has been designed, fabricated indigenously and commissioned on Tokamak Aditya. The system has been commissioned to operate between 20.0 and 47.0 MHz at a maximum power of 200 kW continuous wave (CW). Duration of 500 ms is sufficient for operation on Aditya, however, the same system feeds the final stage of the 1.5 MW ICRH system being prepared for the steady-state superconducting tokamak (SST-1) for a duration of 1000 s. Radio frequency (RF) power (225 kW) has been generated and successfully tested on a dummy load for 100 s at 30.0 MHz. Lower powers have been coupled to Aditya in a breakdown experiment. We describe the system in detail in this work.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.