Abstract
In SST-1, 42GHz ECRH system has been commissioned to carry out breakdown and heating experiments at 0.75T and 1.5T operating toroidal magnetic fields. The 42GHz ECRH system consists of high power microwave source Gyrotron capable to deliver 500kW microwave power for 500ms duration, approximately 20 meter long transmission line and a mirror based launcher. The ECRH power in fundamental O-mode & second harmonic X-mode is launched from low field side (radial port) of the tokamak. At 0.75T operation, approximately 300 kW ECH power is launched in second harmonic X-mode and successful ECRH assisted breakdown is achieved at low loop_voltage ~ 3V. The ECRH power is launched around 45ms prior to loop voltage. The hydrogen pressure in tokamak is maintained ~ 1×10 -5 mbar and the pre-ionized density is ~ 4×10 12 /cc. At 1.5T operating toroidal magnetic field, the ECH power is launched in fundamental O-mode. The ECH power at fundamental harmonic is varied from 100 kW to 250 kW and successful breakdown is achieved in all ECRH shots. In fundamental harmonic there is no delay in breakdown while at second harmonic ~ 40ms delay is observed, which is normal in case of second harmonic ECRH assisted breakdown.
Highlights
The electron cyclotron resonance heating (ECRH) has shown several advantages from plasma start-up to MHD control in various tokamaks [1,2,3,4,5,6,7,8,9]
The 42GHz/500kW ECRH system is used in tokamak SST-1 [10] to carry out experiments related ECRH assisted breakdown and start-up at fundamental and second harmonic
At 0.75T operation, approximately 300kW ECH power is launched in second harmonic X-mode and successful ECRH assisted breakdown is achieved at low loop voltage ~ 3V
Summary
The electron cyclotron resonance heating (ECRH) has shown several advantages from plasma start-up to MHD control in various tokamaks [1,2,3,4,5,6,7,8,9]. The 42GHz/500kW ECRH system is used in tokamak SST-1 [10] to carry out experiments related ECRH assisted breakdown and start-up at fundamental and second harmonic. The 42GHz ECRH system consists of Gyrotron, transmission line and a mirror based launcher. The Gyrotron is tested on dummy load, after successful testing at full parameters on dummy load, the system is connected to tokamak using corrugated waveguide based transmission line system. The plasma breakdown and start-up experiments at fundamental and second harmonic are carried out in SST-1 using 42GHz ECRH system. At 0.75T operation, approximately 300kW ECH power is launched in second harmonic X-mode and successful ECRH assisted breakdown is achieved at low loop voltage ~ 3V. The 42GHz ECRH system consists of high power Gyrotron, corrugated waveguide based transmission line and a mirror based launcher. The typical ECRH pulse (Gyrotron operation on dummy load) at full parameters is shown in figure 3
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