Search

The infrared (IR) thermography diagnostic has recently been upgraded to achieve real-time temperature measurement and feedback capability in the experimental advanced superconducting tokamak (EAST). A new control and data acquisition program for IR camera is developed with online temperature calibration and compensation. Reflective memory (RFM) is configured in the data acquisition system for real-time data transmission to the plasma control system (PCS). Based on the upgraded IR thermography diagnostic, detachment plasma has been achieved for the first time in EAST with active temperature feedback. The divertor impurity seeding system is used to inject a sequence of short neon impurity pulses with 50% D2 to increase the edge radiation of the plasma particles. The temperature of the divertor target plates decreases to the preset target value and the divertor detachment has been realized with no serious reduction of plasma stored energy and confinement observed in the temperature feedback control phase. As a new feedback control method, the IR temperature feedback control shows great application prospects for the temperature and heat flux control of the first wall components in future long pulse operation of EAST. [ABSTRACT FROM AUTHOR]

The Experimental Advanced Superconducting Tokamak (EAST) has demonstrated, for the first time, long-pulse divertor plasmas over 400 s, entirely driven by lower hybrid current drive (LHCD), and further extended high-confinement plasmas, i.e. H-modes, over 30 s with predominantly LHCD and advanced lithium wall conditioning. Many new and exciting physics results have been obtained in the quest for long-pulse operations. The key findings are as follows: (1) access to H-modes in EAST favours the divertor configuration with the ion ∇B drift directed away from the dominant X-point; (2) divertor asymmetry during edge-localized modes (ELMs) also appears to be dependent on the toroidal field direction, with preferential particle flow opposite to the ion ∇B drift; (3) LHCD induces a striated heat flux (SHF), enhancing heat deposition away from the strike point, and the degree of SHF can be modified by supersonic molecule beam injection; (4) the long-pulse H-modes in EAST exhibit a confinement quality between type-I and type-III ELMy H-modes, with H98(y,2) ∼ 0.9, similar to type-II ELMy H-modes. [ABSTRACT FROM AUTHOR]

The lower hybrid wave (LHW) heating experiments at the Experimental Advanced Superconducting Tokamak (EAST) show a wide range of similarities to effects known from applied resonant magnetic perturbations (RMPs) by in-vessel or external magnetic perturbation coils. These observations suggest a current flow understood to be along scrape-off layer (SOL) field lines; here called helical current filaments (HCFs). For a better understanding of the experimental observations, a model to incorporate the magnetic perturbation of HCFs in the magnetic topology has been developed. Modelled SOL field lines, starting in front of the LHW antenna, show agreement in position and pitch-angle with the experimentally observed radiation belts. The comparison of the pick-up coil signals and the modelled HCFs' perturbation allows for determination of the current strength depending on the filaments' distance from the plasma edge. Agreement of predicted footprint structures with experimentally observed heat load and particle flux profiles at different toroidal angles in the divertor region is found. Based on the modelling results, the idea of LHW-induced RMPs, originating from the experimental observations, is strongly supported. [ABSTRACT FROM AUTHOR]