Power Balance Estimation in Long Duration Discharges on QUEST

Abstract

Fully non-inductive plasma start-up was successfully achieved by using a wellcontrolled microwave source on the spherical tokamak, QUEST. Non-inductive plasmas were maintained for approximately 3-5 min, during which time power balance estimates could be achieved by monitoring wall and cooling-water temperatures. Approximately 70%-90% of the injected power could be accounted for by calorimetric measurements and approximately half of the injected power was found to be deposited on the vessel wall, which is slightly dependent on the magnetic configuration. The power distribution to water-cooled limiters, which are expected to be exposed to local heat loads, depends significantly on the magnetic configuration, however some of the deposited power is due to energetic electrons, which have large poloidal orbits and are likely to be deposited on the plasma facing components.

Development of Thomson Scattering Measurement System for Long Duration Discharges on the QUEST Spherical Tokamak

“…2 (b)). This indicates that the hydrogen atoms or molecules recycled from the plasma-facing wall increase with time [6]. The H α emission intensity peaks at around 100 s, and decreases with the rise of the plasma current, and is controlled at a constant level from 300 s onward.…”

“…In QUEST spherical tokamak, the temperature of plasma-facing metal wall (called hot wall) can be heated up to 400 • C to control the recycling. An 8.2 GHz (40 kW) microwave source has been used to launch EC wave, which enables long duration discharges [6]. Experiments have been conducted at various wall temperatures using the hot wall [7].…”

Investigation of hydrogen recycling in long-duration discharges and its modification with a hot wall in the spherical tokamak QUEST

“…Progress during 2010-2012 and the typical magnetic configurations are reported in [26]. Since the 2012 S/S campaign, a power balance has been achieved at a power level of 100 kW and the main issue is now particle balance [23,24]. The hot wall was installed in the 2014 A/W campaign and active heating of the hot wall is available.…”

Study on the effect of EAST divertor geometric accuracy on heat load distribution

“…And the surface thermocouple sensor, calorimeter probe and Langmuir probe are applied in (KSTAR) [10], JET [11] and EAST [12] device to study the heat load on PFCs. Besides, calorimetry systems are employed in QUEST [13] and TRIAM-1M [14,15], results from QUEST show that heat load exhausted by cooling water is 70%-90% of the injected power [13]. Dedicated calorimetry system in TRIAM-1M provides accurate heat load analysis results during long pulse discharges, and the total heat load coincides with the accumulated injection energy [14].…”