Design of real-time feedback control of vertical growth rate on EAST

Real-time feedback control of vertical growth rate,called gamma control,has been successfully applied to experimental advanced superconducting tokamak(EAST).In this paper,a new gamma control method is proposed to regulate the vertical growth rate,which is an estimator of plasma vertical instability.Thus,the gamma controller can be utilized to keep the tokamak plasma away from its unstable boundary.In this work,the main development process includes three steps:(1)real-time implementation of model-based vertical growth rate calculation,taking advantage of GPU parallel computing capability,(2)design of plasma shape response for dynamic shape control using a slight modification to the plasma boundary,and(3)development of a gamma control algorithm integrated into the EAST plasma control system(PCS).The gamma control was experimentally verified in the EAST 2019 experiment campaign.It is shown that the time evolution of the real-time vertical growth rate agrees with the target value,indicating that the real-time vertical growth rate can be regulated by gamma control.

Tests of the real-time vertical growth rate calculation on EAST

In order to measure controllability of vertical instability in EAST,the calculation of model-based vertical growth rate,called rt-gamma,has been successfully carried out in real time.The numerical computing method is adapted from rigid plasma response model in TokSys,which is a widely-used analysis tool for tokamak devices in Matlab environment,but the code is rewritten by taking advantage of GPU parallel computing capability to accelerate the computation.The calculation of rt-gamma is validated by comparing it with the corresponding result generated by TokSys for totally 3508 cases.It is shown that the average absolute value of relative errors is about 0.85%.In addition,the calculation program of rt-gamma has been successfully applied during 2019 EAST campaign.The comparison with experimental results is discussed in this paper.The real-time calculation tool is well able to calculate model-based vertical growth rate,which is convenient for fast and continuous evaluations of EAST control system stability performances.

Vertical two-dimensional WS_(2)flakes grown on flexible CNT film for excellent electrochemical performance

Soft electrochemical actuators that can generate mechanical motions in response to electrical stimuli can be used as artificial muscles in microscale robots.The electrode materials are the key component of the electrochemical actuator because they limit the ion diffusion and accumulation processes and thus affect the deformation in fast response-time and potential engineering applications.Low-dimensional materials,such as one-dimensional(1D)CNT and two-dimensional(2D)vertically stood WS_(2),are great electrode due to their good electrochemical stability and high surface-to-volume ratios,but show limited performances when being used on their own in the actuators because of low reconstruction or low conductivity.A combination of 1D CNT and 2D WS_(2)could form a heterojunction with both high electrochemical activity and great mechanical stability.Herein,by depositing highly disordered graphene nanosheets(HDGNs)on CNT films and then WS_(2)on the formed low-dimensional nanocarbon film,a hybrid WS_(2)/HDGN/CNT film was synthesized through a multistep CVD method.Vertically grown WS_(2)nanosheets were achieved by taking advantage of HDGNs which limits CNTs sliding.So,the volume expansion caused by the transition from WO_(3)to WS-2can force the vertical growth of WS_(2).This hybrid film shows excellent electrochemical properties,such as high specific capacitance and high rate performance.Soft actuators based on the WS_(2)/HDGN/CNT films show good actuating performance,including stability and reconfigurability.

Versatile and scalable chemical vapor deposition of vertically aligned MoTe2 on reusable Mo foils

Layered MoTe2 has shown great promises for optoelectronics and energy-storage applications due to its exceptional optical and electrochemical properties.To date,considerable efforts have been devoted to fabricating layered MoTe2 with lateral orientation by means of mechanical/chemical exfoliation and chemical vapor deposition(CVD)methods.As compared to its horizontal counterparts,vertically aligned MoTe2 with higher density of active edge sites is expected to possess unique optoelectronic and electrochemical properties,while which has not been reported yet.In this work,we report a versatile and scalable CVD growth of vertically aligned MoTe2 with length of up to〜7.5 fjm on Mo foil.Remarkably,the dominant phase of the vertically aligned MoTe2 can be tuned from 2H to 1T’by increasing the growth temperature from 630 to 7800C.Owing to the weak interaction between the as-grown MoTe2 and Mo foil,the as-grown MoTe2 can be easily detached from the Mo foil.This in turn enabled economic reuse of the Mo foil for multiple growth.Moreover,the vertical growth of the MoTe2 is proposed to be caused by the internal strain generated during tellurization of Mo foil.Furthermore,the as-grown MoTe2 can also be directly dispersed in solvent to produce high-quality MoTe2 nanosheets.The versatility of this growth strategy was further demonstrated by fabricating other vertically aligned transition metal chalcogenides(TMDs)such as TaTe2 and MoSe2.Hence,this work paves the path towards achieving unique TMDs structures to enable high-performance optoelectronic and electrochemical devices.