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Overview of Recent Experimental Results in the ADITYA-U Tokamak J MF1-I15 AAPPS-DPP2020 4th Asia-Pacific Conference on Plasma Physics, 26-31Oct, 2020, Remote e-conference Overview of recent experimental results in the ADITYA-U Tokamak J. Ghosh*1, R.L. Tanna1, Rohit Kumar1, Tanmay Macwan1, Harshita Raj1, K.A. Jadeja1, K.M. Patel1, Suman Aich1, Kaushlender Singh1, Suman Dolui1, D.S. Varia1, D.H. Sadharakiya1, B.K. Shukla1, M.N. Makawana1, K.S. Shah1, Shivam Gupta1, V. Balakrishnan1, C.N. Gupta1, V.K. Panchal1, Praveenlal E. V.1, B. Arambhadiya1, Minsha Shah1, Pramila Gautam1, V. Raulji1, Praveena Kumari1, R. Rajpal1, Nandini Yadava1, Sharvil Patel, Nilam Ramaiya1, M.B. Chowdhuri1, R. Manchanda1, R. Dey1, G. Shukla, K. Shah, N. Bisai1, P.K. Atrey1, S.K. Pathak1, U. Nagora1, Kiran Patel1, Varsha Siju1, J.V. Raval1, S. Purohit1, Manoj Kumar1, K. Tahiliani1, D. Kumawat1, S.K. Jha1, M.V. Gopalkrishana1, Bhavesh Kadia1, D. Raju1, B. R. Doshi1, P. K. Chattopadhyay1, Y.C. Saxena1, A. Sen1, S. Chaturvedi1, Sambaran Pahari2, Adityanandan Savita2, P. Rahulnath2, P. K. Maurya2, Saroj jha2, K. Raghvendra2, Neeraj Shiv2, B. Nagaraju2, Sukant Mahar2, I.V.V. Suryaprasad2 and R. Pal3 1Institute for Plasma Research, Gandhinagar 382428 India 2 CAD, Bhabha Atomic Research Centre, Visakhapatnam 531011 India 3Saha Institute of Nuclear Physics, Kolkata 700064 India e-mail (speaker): [email protected] 19 -3 The ADITYA Upgrade (ADITYA-U) (R 0 = 75 cm, a= 25 x 10 m ) of plasma density as compared to the H2 puffed cm) tokamak is capable of producing circular and shaped Ohmic discharges (~3 x 1019 m-3), indicating lower electron plasma with single and double null open divertor density threshold for toroidal rotation reversal with neon configurations. The foremost objective of ADITYA-U is to seeding. The rotation reversal is not accompanied by usually prepare the physics and the technological base for larger observed turbulence reduction in the plasma edge. Neon machine including ITER. Since obtaining its first circular &amp; argon seeding also leads to radiative improved mode plasma in December, 2016, plasma parameters close to the (doubling of energy confinement time). Periodic short design parameters of circular plasmas in limiter hydrogen gas puffs are found to concomitantly decrease the configuration have been realized in ADITYA-U and the drift-tearing mode rotation frequency and the mode shaped plasma operation has been initiated in H2 and D2. amplitude leading to periodic modulation of the rotation Emphasis has been given to experiments on runaway frequency and amplitude of DT modes. This has been found electrons (REs), disruption studies using novel particle to be due to flattening of plasma pressure in the edge region injection techniques, plasma rotation reversals, radiative- with gas puffs. BOUT++ code simulations support such a improved modes with Ne, Ar gas injection and MHD modes reduction in diamagnetic drift frequency. The SMBI fueling modification, cold-pulse propagation, plasma detachment led to enhancement of magnetic field stochastization which using periodic fuel gas-puffs. Extensive wall conditioning increased the RE transport. 42 GHz ECR assisted low loop using novel pulsed-GDC along with lithium coating resulted voltage (Electric field ~ 2 V/m) start-up has also been in consistent circular plasma discharges with plasma current successfully achieved. This paper summarizes the ~ 180 kA, plasma duration of ~ 350 ms, Chord-averaged experimental research of ADITYA-U tokamak in the key electron density ~ 3 – 6 x 1019 m-3 and central electron areas of thermo-nuclear fusion. temperature ~ 500 eV at toroidal magnetic field ~ 1.2 - 1.4 T. Figure 1 Figure 2 The experiments on REs showed that the suppression and recovery of the HXR intensity strongly coincide with the suppression and recovery of turbulent edge fluctuations, which indicates a significant role of edge fluctuations on REs (Figure 1). Furthermore, the REs are confined using an electrostatic field induced by biasing an electrode placed in the edge region. In a major development towards disruption mitigation techniques, faster current quench times have been obtained Correlation of HXR with density Discharges with pellet (#33317, during particle injection using electromagnetically driven fluctuation in presence of gas puff black curve) and without pellet (# payloads, carried out for the first time in ADITYA-U. The 33318, red curve), impurity particles reached the core within ~ 1.25 ms and [1] Effect of periodic gas-puffs on drift-tearing modes in cause fast termination of plasma current in < 2 ms (Figure 2). ADITYA/ADITYA-U tokamak discharges, Harshita Raj, Disruptive discharge analysis showed that the current quench J. Ghosh et al, Nucl. Fusion 60 (2020) 036012. time during disruption is inversely proportional to the pre- [2] Overview of Operation and Experiments in the ADITYA- disruptive values of edge safety factor, q , and is strongly a U tokamak, R.L. Tanna, J. Ghosh, et al, Nucl. Fusion correlated with the prevailing pre-disruptive plasma MHD 59 (2019), Number 11, 112006 activities. In neon gas puffed discharges of ADITYA-U, reversal of toroidal rotation occurred at lower values (~ 1.8 .
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