Magnetic Confinement Fusion Part 1. Tokamaks, and plasma physics in Tokamaks Part 2. ITER for fusion, and JET for ITER Hyun-Tae Kim ([email protected]) Responsible Officer for JET campaigns EUROfusion Consortium IAEA-ICTP College on Plasma Physics, 2 Nov 2018, Trieste, Italy, Contents Part 1. 1) Nuclear fusion and Tokamaks 2) Plasma physics in Tokamaks a) Equilibrium b) Stability c) Transport Part 2. 1) ITER’s goal 2) What we are now doing for ITER a) EUROfusion Roadmap b) Joint European Torus c) Fusion research at JET Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 2 Contents Part 1. 1) Nuclear fusion and Tokamaks 2) Plasma physics in Tokamaks a) Equilibrium b) Stability c) Transport Part 2. 1) ITER’s goal 2) What we are now doing for ITER a) EUROfusion Roadmap b) Joint European Torus c) Fusion research at JET Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 3 Nuclear fusion, the energy source of the sun Mass / Number of NumbernucleonsMass / Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 4 Why fusion energy? ✓ No greenhouse emissions ✓ No long-lived radioactive waste ✓ Intrinsically safe ✓ Infinite fuel ( >100 million years) e.g. 40tons Coal = 7g D +10.5g T Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 5 How to make fusion happen? 3.5 MeV 14.1 MeV • Electrostatic repulsion between nuclei • To overcome it, very high temperature (~108 °C) and high density required • Fully ionized at such high temperature for fusion i.e. plasma • Perpendicular motion of charged particles limited by magnetic fields • Doughnut-shape magnetic fields needed to prevent parallel particle loss • Thermonuclear fusion in this way is called Magnetic Confinement Fusion (MCF). Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 6 Two concepts of MCF devices Torodial direction Poloidal direction https://fusion4freedom.com • Tokamaks e.g. JET, K-STAR, EAST, WEST, ASDEX-U, TCV, MAST-U • Stellarators e.g. Wendelstein 7-X, LHD • Main difference: Poloidal magnetic fields are generated by ✓ plasma current in Tokamaks (i.e. pulsed operation), and ✓ electric current in external coils in Stellarators (i.e. steady state operation) • So far, Tokamaks have shown higher fusion performance than Stellarators. Hence, ITER is also designed as a Tokamak. First fusion power plant is likely to be a Tokamak, although Stellarators can be a long-term alternative. • This lecture will focus on Tokamaks. Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 7 Tokamak – Vacuum vessel Low gas pressure ( ~5e-8 atm) is needed to make and keep a R0 a plasma. Donut-shaped vacuum vessel R0 = 6.2 m, a = 2.0 m in ITER R0 = 3.0 m, a = 1.0 m in JET Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 8 Tokamak – Toroidal Field coils Torodial direction Poloidal direction Toroidal Field (TF) coil ion Toroidal Magnetic field electron Toroidal magnetic field B 5.3 T in ITER and 3.0 T in JET (32 TF coils with 24 turns each) Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 9 Tokamak - http://hyperphysics.phy- astr.gsu.edu/hbase/magnetic/toroid.html BJ = 0 B ()()B dS = J dS 0 B= dl N I 0 TF TF NI B = 0 TF TF 2R B I[] MA B[ Tesla ]== 6.4TF , for JET with N 32. Rm[] TF R Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 10 Tokamak – Charge seperation Drift velocity of charged particles FB ion electron V = D qB2 ion +++ with centrifugal force Fcf mv2 B B V =e D,R Rr qB2 - - - with B force FB electron B 1 VBD, B = − B B(R) qB2 R R Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 11 Tokamak – ExB drift loss Drift velocity of charged particles ion electron FB V = D qB2 ion +++ with electric force FE B E V =qE Particle loss D,R qB2 - - - due to ExB drift electron Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 12 Tokamak – ExB drift loss Torodial direction Poloidal direction ion +++ - - - Poloidal magnetic field needed electron to avoid the charge seperation (and to stabilize plasma instabilities) → Plasma current needed Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 13 Tokamak – Central Solenoid for Vl http://www.electronics- tutorials.ws/electromagnetism/electromagnetic- Central Solenoid (CS) induction.html Faraday`s law d V =− cs l dt where csI cs Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 14 Tokamak – Ip and Bp http://www.electronics- tutorials.ws/electromagnetism/electromagnetic- Central Solenoid (CS) induction.html Faraday`s law d V =− cs l dt Plasma current where csI cs Poloidal magnetic field V = l Ip BIpp Rp Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 15 Tokamak - Pulsed operation Inductive Ip drive → pulsed operation Intrinsic problem in tokamaks. Plasma Current Ip Not desirable for power plant time CS Coil Current Ics Ics Limit due to mechanical stress and ohmic heating in CS time d VI= −cs where ldt cs cs dI Vl cs Vl − Ip = dt Courtesy of Yong-Su Na (SNU) Rp Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 16 Tokamak - Steady state operation For steady-state operation, Ip should be driven by non-inductive ways Plasma Current Ip e.g. LHCD, ECH, NBI, Bootstrap current time CS Coil Current Ics time d VI= −cs where ldt cs cs dI VV −cs = 0 lldt Courtesy of Yong-Su Na (SNU) Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 17 Tokamak – Poloidal (vertical) field coils current current Poloidal Field coils Attractive Lorentz X Force ● X current current X X Repulsive Lorentz Plasma positioning and shaping ● Force by electric current in PF coils X Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 18 Tokamak, Magnetic Confinement Fusion Reactor Central Solenoid Poloidal B field Iron man 2008 Helical B field TF coils Plasma current Toroidal B field Toroidal magnetic field (by electric current in TF coils) + Poloidal magnetic field (by plasma current) = Helical magnetic field → Closed magnetic flux surfaces → High confinement Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 19 World’s first Tokamak • T1 tokamak : world’s first tokamak device, operated in 1952 in Kurchatov Institute, Moscow, Russia • Russian pioneers invented to suppress the kink instability • 0.4 m3 Plasmas were produced in its copper vacuum vessel. • The Russian pioneers named it https://www.iter.org/sci/BeyondITER in Russian, Tokamak • Toroidalnaja kamera s magnitnymi katushkami, Toroidal chamber with magnetic coils in English Andrei Sakharov Igor Tamm Lev Artsimovich Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 20 Tokamak in present days JET (Joint European Torus): R0 = 3 m, a = 1 m, operated since 1983, refurbished in 2011 Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 21 Fusion power plant D + T → n (14.1MeV) + α (3.5 MeV) ➢ Li Blanket ➢ Plasma heating (self-sustaining) 1. Heat generation →electricity 2. T breeding ❖ T breeding n + Li6 → α + T + 4.8 MeV n + Li7 → α + T + n – 2.5 MeV Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 22 Fusion power Pfus = Vp n D n T 17.6 MeV for ni =2n D =2n T 2 and TTii(for = 10-20keV) 2 2 2 Pfus = nii T p Fusion reaction rate reaction Fusion For high fusion power and self - sustainment, high plasma pressure is essential. http://www.scienceall.com/jspJavaPopUp.do?classid= CS000140&articleid=611&bbsid=146&popissue=java Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 23 High and stable plasma pressure is necessary for high fusion power Tokamak plasma Plasma pressure profile aimed in tokamaks Core Poloidal cross section Edge pressure Pedestal Edge Transport Barrier SOL distance from centre Courtesy of C. Maggi (CCFE) Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 24 Contents Part 1. 1) Nuclear fusion and Tokamaks 2) Plasma physics in Tokamaks a) Equilibrium b) Stability c) Transport Part 2. 1) ITER’s goal 2) What we are now doing for ITER a) EUROfusion Roadmap b) Joint European Torus c) Fusion research at JET Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 25 Plasma physics is essential for high and stable plasma pressure in tokamaks Equilibrium Transport Stability Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 26 Plasma equilibrium p = J B Force balance between p Outward plasma pressure and Inward magnetic pressure JB Hyun-Tae Kim | IAEA-ICTP plasma college | Trieste, Italy | 2 Nov 2018 | Page 27 Plasma equilibrium B p = 0, p is constant along B p = J B J p = 0, p is constant along J Magnetic flux surfaces are imaginary surfaces on which Magnetic flux surface p is uniform, and p BJ and lie (i.e. don't accross the surfaces). Enclosed magnetic flux is the same everywhere (hence name). The surfaces are labelled by the enclosed magnetic flux i.e. toroidal flux or poloid al flux , crossing the colored area. d rB # of toroidal turn of the field line Safety factor q( ) = e.g. q=4 d R0 B # of poloidal turn of the field line i.e.