High Power ICRH Systems

Overview

Ion Cyclotron Resonance Heating (ICRH) aims to generate and deliver RF power in tokamaks like ADITYA-U and SST-1 for experiments such as line-conditioning, heating, pre-ionization, and current drive. The ICRH system consists of three main components: RF amplifiers, transmission line components, and ICRH antennas. The ICRH Antenna system propagates the High Power RF and heats ions in magnetically confined plasma by coupling MHz RF waves, which deposit energy in the ions through the cyclotron heating mechanism. At present, three independent RF amplifiers are in operation stages and connected with both ADITYA-U & SST-1 Tokamaks.

200 KW, 24.8 MHz RF Amplifier connected with ADITYA-U & may extend up to SST-1.
1.5 MW, 24.8 MHz RF Amplifier connected with ADITYA-U & may extend up to SST-1.
1.5 MW, 35-65 MHz CEC Amplifier connected with ADITYA-U & SST-1.

Section Present Status & Achievement

ICRH RF Section has developed two indigenous RF Generator chains having 2 kW, 20 kW, and 200 kW / 1.5 MW stage placed at ICRH Lab and one system at SST-1.
ICRH Electrical Section has developed indigenous Filament, Control & Screen grids and Anode power supplies for all ratings of RF amplifiers.
ICRH Transmission & Antenna section has developed & laid more than 300 meters of Copper and Aluminum transmission lines and its components like Bend, Reducers, Directional Coupler, Matching Network, VTL, and Antenna, etc. for SST-1 & ADITYA-U.
ICRH-DAC has developed an indigenous Data Acquisition & Control system for online monitoring, real-time controls and protection of the RF amplifier & HV Supplies, Tx Line matching Networks & Diagnostics.

High Power ICRH Systems

Experiments

1.Testing of 24.8MHz-1.5MW RF Source Chain

Initial testing to revive the 1.5MW RF generator has been successful as 160kW RF power at 24.8MHz for 250ms on RF dummy load achieved using a fully in-house developed system comprising RF generator, power supplies, transmission line and DAC system. For input RF feed in house devolved 2 kW & 20kW RF source used. For the Anode bias RHVPS has been used. The amplifier will be gradually scaled up to achieve higher power with large on time.

2.Testing of 200kW, 24.8MHz RF Source Chain

Initial testing to revive the tetrode-tube–based 200 kW, 24.8 MHz RF generator at the ICRH Lab has been successfully completed. RF power levels of up to 130 kW were generated and tested in various operating modes, with a maximum pulse duration of 1 second, using an RF dummy load. The amplifier was fully integrated and operated using an entirely in-house–developed system comprising the RF generator (2 kW, 20 kW stage as input feed), power supplies (filament, control grid, screen grid & anode) transmission line, and Data acquisition control system.

3.Plasma Production & Up-gradation of Antenna Tests Facility (ATF)

The ATF(Antenna Test facility) is an in-vessel test facility( 1/6th part of Aditya tokamok ) for ICRH antennas, developed with the objective of evaluating key antenna parameters, primarily the field profile, probe diagnostic and power coupling efficiency prior to their application in a tokomak. The system is integrated with a 1 kW RF source (20-40 MHz) & matching networks to launch maximum power. One major RF design issue identified i.e. discontinuity in the RF feed that was causing RF reflection and intermittent glow discharge. To resolve this, new RF window designed, fabricated & integrated with ATF for fully continuous and balanced feed.

4.High Power RF Testing of Vacuum Window for SST-1 tokomak

The RF vacuum window is critical part of ICRH Vacuum Transmission line (VTL) primarily used to separate the SST1 tokamak vessel vacuum to ICRH ex-vessel system. It provide a mechanical support between inner and outer conductors of VTL. To test & qualify this component for performance evaluation a High voltage and high power RF test setup is prepared in the ICRH Lab with indigenously developed high power RF source (200 kW) & Tx line components( RF vacuum window and water cooled dummy load). The high power RF tested successfully into various operation mode successfully with maximum RF Power 130 kW (available power) at 24.8 MHz with dummy load. HVDC Breakdown tested successfully upto available test facility of 40KV.