Overview of spherical tokamak research in Japan

Nationally coordinated research on spherical tokamak is being conducted in Japan. Recent achievements include: (i) plasma current start-up and ramp-up without the use of the central solenoid by RF waves (in electron cyclotron and lower hybrid frequency ranges), (ii) plasma current start-up by AC Ohmic operation and by coaxial helicity injection, (iii) development of an advanced fuelling technique by compact toroid injection, (iv) ultra-long-pulse operation and particle control using a high temperature metal wall, (v) access to the ultra-high-β regime by high-power reconnection heating, and (vi) improvement of spherical tokamak plasma stability by externally applied helical field.

[1]  A. Ejiri,et al.  Numerical modeling of lower hybrid current drive in fully non-inductive plasma start-up experiments on TST-2 , 2017 .

[2]  M. Ono,et al.  Development of over-MW gyrotrons for fusion at 14 GHz to sub-THz frequencies , 2017 .

[3]  Laila A. El-Guebaly,et al.  Fusion nuclear science facilities and pilot plants based on the spherical tokamak , 2016 .

[4]  A. Fukuyama,et al.  Power Balance Estimation in Long Duration Discharges on QUEST , 2016 .

[5]  T. Fujita,et al.  Measurement of Tokamak Plasma with the External Helical Field Using a High-Speed Camera in TOKASTAR-2 , 2016 .

[6]  A. Ejiri,et al.  RF Central Solenoid Operation for Plasma Production and Current Drive in TST-2 , 2016 .

[7]  M. Nagata,et al.  Characteristics of Plasma Current Start-Up by Transient Coaxial Helicity Injection on HIST , 2016 .

[8]  Hitoshi Tanaka,et al.  Shift in principal equilibrium current from a vertical to a toroidal one towards the initiation of a closed flux surface in ECR plasmas in the LATE device , 2016 .

[9]  A. Fukuyama,et al.  Particle balance in long duration RF driven plasmas on QUEST , 2015 .

[10]  A. Ejiri,et al.  Non-inductive plasma start-up experiments on the TST-2 spherical tokamak using waves in the lower-hybrid frequency range , 2015 .

[11]  T. Fujita,et al.  Magnetic Field Measurements Using a Multichannel Magnetic Probe in TOKASTAR-2 , 2015 .

[12]  R. Raman,et al.  Plasmoids Formation During Simulations of Coaxial Helicity Injection in the National Spherical Torus Experiment. , 2015, Physical review letters.

[13]  R. Scannell,et al.  High power heating of magnetic reconnection in merging tokamak experimentsa) , 2015 .

[14]  A. Hirose,et al.  Design and implementation of fast charging circuit for repetitive compact torus injector , 2014 .

[15]  M. C. ArchMiller,et al.  Suppression of vertical instability in elongated current-carrying plasmas by applying stellarator rotational transforma) , 2014 .

[16]  T. Fujita,et al.  Optimization of Tokamak Plasma Equilibrium Control in TOKASTAR-2 , 2014 .

[17]  S. Okamura,et al.  Role of energetic electrons during current ramp-up and production of high poloidal beta plasma in non-inductive current drive on QUEST , 2014 .

[18]  Hitoshi Tanaka,et al.  Circular TE11-based waveguide polarizer for efficient coupling to electron Bernstein wave , 2013 .

[19]  Hitoshi Tanaka,et al.  Open field equilibrium current and cross-field passing electrons as an initiator of a closed flux surface in EC-heated toroidal plasmas , 2012 .

[20]  Y. Nagayama,et al.  A Conceptual Design of Superconducting Spherical Tokamak Reactor , 2012 .

[21]  M. Inomoto,et al.  Ion and electron heating characteristics of magnetic reconnection in a two flux loop merging experiment. , 2011, Physical review letters.

[22]  Hirohisa Hara,et al.  PLASMA MOTIONS AND HEATING BY MAGNETIC RECONNECTION IN A 2007 MAY 19 FLARE , 2011 .

[23]  B. Leblanc,et al.  Demonstration of Tokamak ohmic flux saving by transient coaxial helicity injection in the national spherical torus experiment. , 2010, Physical review letters.

[24]  T. Maekawa,et al.  Rapid current ramp-up by cyclotron-driving electrons beyond runaway velocity. , 2010, Physical review letters.

[25]  Y. Kamada,et al.  SlimCS—compact low aspect ratio DEMO reactor with reduced-size central solenoid , 2007 .

[26]  T. Maekawa,et al.  Spontaneous formation of closed-field torus equilibrium via current jump observed in an electron-cyclotron-heated plasma. , 2006, Physical review letters.

[27]  Hitoshi Tanaka,et al.  A survey of mode-conversion transparency windows between external electromagnetic waves and electron Bernstein waves for various plasma slab boundaries , 2006 .

[28]  E. D. Fredrickson,et al.  A component test facility based on the spherical tokamak , 2005 .

[29]  M. Nagata,et al.  Characteristics of modified CT injector for JFT-2M , 2004 .

[30]  Farrokh Najmabadi,et al.  Spherical torus concept as power plants—the ARIES-ST study , 2003 .

[31]  J. Miyazawa,et al.  Compact toroid injection experiment in JFT-2M , 1999 .

[32]  P. Bellan,et al.  Effects of CT injector acceleration electrode configuration on tokamak penetration , 1998 .

[33]  G. Pacher,et al.  Experimental demonstration of tokamak fuelling by compact toroid injection , 1997 .

[34]  H. Ikezi,et al.  Semi‐stellarator field stabilization of tokamak plasma , 1979 .

[35]  A. Fukuyama,et al.  Kinetic Full Wave Analysis of Electron Cyclotron Wave Mode Conversion in Tokamak Plasmas , 2016 .

[36]  A. Ejiri,et al.  Fully Non-Inductive Current Drive Experiments Using 28 GHz and 8.2 GHz Electron Cyclotron Waves in QUEST , 2014 .

[37]  Mizuki Sakamoto,et al.  Steady-State Operation Scenario and the First Experimental Result on QUEST , 2010 .