2024 – RF Systems Commissioning

RF Systems Commissioning

2024 Research Campaign, Heating and Current Drive

Purpose of Experiment

The purpose of this experiment is to commission or re-commission any or all of DIII-D’s RF systems to ensure readiness of the systems for the experimental campaign. Each system has various needs that can be combined to minimize the experimental run time needed. The focus of this experiment will primarily be the helicon system, which must be conditioned to reach adequate power levels and pulse lengths for experiments; however, since the specific requirements on the plasma conditions for helicon conditioning purposes are relatively undemanding, this experiment may also be used to commission either of the other two RF systems at DIII-D via piggyback or otherwise.

Experimental Approach

The conditioning process consists of repeated helicon RF pulses into L-mode discharges. Since the conditioning of the vacuum transmission line just needs a tokamak plasma to load the antenna, the specific requirements are low and the helicon system makes progress with conditioning even with Ohmic plasmas in which first-pass absorption of the helicon is relatively poor. Previous campaigns have used shot 187313 as a target discharge for conditioning (without ECH) but any target shot with plasma present is useful. The target shot is a lower single null L-mode discharge with reversed BT and normal IP, but the antenna is also optimized for operation into normal BT and reversed IP. Conditioning progress may also be made in any other BT/IP configuration. The helicon system will begin conditioning into vacuum at a power level of about 0.4 MW klystron forward power; once antenna operation is stable for a given power and pulse length, the power and/or pulse length will be raised. The system will begin firing co-current (from 150); once this is conditioned, the counter-current (210) side will need to be conditioned as well.