Burning Plasma Relevant Control Development: Advanced Magnetic - PowerPoint PPT Presentation

Burning Plasma Relevant Control Development: Advanced Magnetic Divertor Configurations, Divertor Detachment and Burn Control by E. Kolemen 1 with B.A. Grierson 2 , R. Nazikian 2 , W. Solomon 2 , S.L. Allen 3 , M.A. Makowski 3 , V.A. Soukhanovskii 3 , B.D. Bray 4 , D. Eldon 4 , D.A. Humphreys 4 , A. Hyatt 4 , R. Johnson 4 , A.W. Leonard 4 , C. Liu 4 , C. Paz-Soldan 4 , B.G. Penaflor 4 , T.W. Petrie 4 , A.G. McLean 5 , E.A. Unterberg 5 , and S. Wolfe 6 1 Princeton University, NJ USA 2 Princeton Plasma Physics Laboratory, Princeton, NJ, USA Detachment Control 3 Lawrence Livermore National Laboratory, Livermore, CA, USA 4 General Atomics, San Diego, CA, USA 5 Oak Ridge National Laboratory, Oak Ridge, TN, USA 6 MIT, Cambridge, MA, USA Presented at the 25 th IAEA Fusion Energy Conference Saint Petersburg, Russia Burn Control October 13 – 18, 2014 Snowflake Control 1 E. Kolemen /IAEA/ Oct 2014

Focus: How to Achieve Acceptable Heat Flux Exhaust Compatible with Attractive Core Plasma There are technological limits on • heat flux removal , and the problem gets more challenging for future devices High fidelity control gives • opportunity to solve some of these challenges 2 E. Kolemen /IAEA/ Oct 2014

Focus: How to Achieve Acceptable Heat Flux Exhaust Compatible with Attractive Core Plasma There are technological limits on • heat flux removal , and the problem gets more challenging for future devices High fidelity control gives • opportunity to solve some of these challenges 1. Snowflake Divertor: - Reduce peak heat flux - Possibly reactor application 3 E. Kolemen /IAEA/ Oct 2014

Focus: How to Achieve Acceptable Heat Flux Exhaust Compatible with Attractive Core Plasma There are technological limits on • heat flux removal , and the problem gets more challenging for future devices High fidelity control gives • opportunity to solve some of these challenges 1. Snowflake Divertor: 2. Partial detachment control - Reduce peak heat flux - Reduce target plasma - Possibly reactor temperature & erosion application - ITER relevant 4 E. Kolemen /IAEA/ Oct 2014

Focus: How to Achieve Acceptable Heat Flux Exhaust Compatible with Attractive Core Plasma There are technological limits on • heat flux removal , and the problem gets more challenging for future devices 3. Burn control - Regulate High fidelity control gives • heat source opportunity to solve some of - ITER/Reacto these challenges r relevant 1. Snowflake Divertor: 2. Partial detachment control - Reduce peak heat flux - Reduce target plasma - Possibly reactor temperature & erosion application - ITER relevant 5 E. Kolemen /IAEA/ Oct 2014

Heat Flux Reduction via 1. Snowflake Divertor Control 2. Detachment Control 3. Burn Control with 3D Coils 6 E. Kolemen /IAEA/ Oct 2014

• • • – – – • – – – – Snowflake Divertor (SFD) Has Advantages Compared to • – • • the Standard X-point Divertor • • • • • Exact Snowflake 2 2 nd X-Point in 2 nd X-Point in -18 P 4-18 Private Flux SOL -21 Snowflake divertor(SFD): second-order null (2 X-points) • Geometric changes compared to standard divertor can lead to: • – High poloidal flux expansion, large plasma-wetted area  reduce peak q div – Four strike points  share P div E. Kolemen / St. Petersburg / Oct 2014 7

Snowflake Control System SFD (-) I PF Desired + SFD SFD controller - DIII-D SFD locator SFD (+) E. Kolemen / St. Petersburg / Oct 2014 8

Snowflake Locator: Finding the Two X-points Locally expand the Grad-Shafranov • equation in toroidal coordinates: I PF Desired + SFD SFD controller - DIII-D SFD Keep the 3 rd order terms • locator Y exp = Y ( c exp , d r , d z ) Find coefficients, c exp , from sample • points Find the null points (X-points) <250us • SFD (+) ¶ Y ¶ Y B r = - 1 = 0 = B z = 1 = 0 exp exp ¶ d z ¶ d x r r { d r X 1 ( c exp ), d z X 1 ( c exp ), d r X 2 ( c exp ), d z X 2 ( c exp )}  9 E. Kolemen /IAEA/ Oct 2014 •

Snowflake Control: Controlling the PF Coil Currents Snowflake parameters: θ , ρ , r c , z c • Calculate A matrix which shows • I PF Desired + SFD how PF coils affect X-points (2 ms) SFD controller - DIII-D SFD locator 3 closest PF coils are used for θ • controlling the formation x F4B x ρ x F5B F8B Location of the X-points and Centroid 10 E. Kolemen /IAEA/ Oct 2014

Snowflake Control: Obtaining Exact Snowflake ( ρ Scan) Simulation 11 E. Kolemen /IAEA/ Oct 2014

Snowflake Control: Obtaining Exact Snowflake ( ρ Scan) Simulation 12 E. Kolemen /IAEA/ Oct 2014

Snowflake Control: Obtaining Snowflake (Exact, + and -) Near Exact Snowflake Snowflake Control (Control Starts at 3 s) Obtained long stable S-F close to exact S-F • – No adverse confinement degradation – Pedestal profile for S-F has little change compared to regular divertor – Observed broadening of heat flux profiles with snowflake 13 E. Kolemen /IAEA/ Oct 2014

Snowflake Control: Scanning the Angle Simulation 14 E. Kolemen /IAEA/ Oct 2014

Snowflake Control: Scanning the Angle Simulation 15 E. Kolemen /IAEA/ Oct 2014

Snowflake Control: Angle Control (+80 ° to -45 ° ) Angle requested Angle achieved Time [ms] x x 80 ° x -45 ° x 16 E. Kolemen /IAEA/ Oct 2014

Snowflake with 2.5x Reduced Heat Flux Compatible with High Performance Plasmas standard Snowflake • • • • • • • 4 β N = 3.0 and H98(y,2) ≅ • q ^ (MW/m 2 ) IN OUT IN OUT 1.35 conditions preserved • with SF with no adverse effects RED – Before gas puffing BLUE – Radiating 0 .6-1.3 01.0 -1.3 0 1.0 1.6 -1.3 0 1.0 1.6 -1.3 0 1.0 1.6 -1.3 0 1.0 1.6 – Peak heat flux outer � Z (m) Z (m) R (m) Z (m) R (m) Z (m) R (m) Z (m) R (m) reduced by 2.5x for the SF AT – SF: q P ⊥ ,Iin > q P 17 E. Kolemen /IAEA/ Oct 2014 ⊥ ,out

Heat Flux Reduction via 1. Snowflake Divertor Control 2. Detachment Control 3. Burn Control with 3D Coils 18 E. Kolemen /IAEA/ Oct 2014

Partial Detachment Control Needed for ITER efda.org www.efda.org Not enough detachment  T e and heat flux too high  Erosion • Too much detachment  Instabilities (MARFE) and core degradation • MARFE Instability: • – Full detachment  large cold areas – Neutrals/Impurities influx  high radiation from the core – Thermal instability of the whole plasma 19 E. Kolemen /IAEA/ Oct 2014

Effective Detachment Control at Constant Core Density Requires Two Feedback Channels D 2 Fueling: Goal: Keep the core density and • Core Density Control detachment level constant Feedback Control Method: • Upper + Core Density Density Gas Request controller - Valve Interferometer Chord Density Meas. (Interferometer) Lower + Detachment Detachment Gas RT-Divertor Request controller Thomson - Valve Detachment Meas. (rt-Divertor Thom.) D 2 Fueling: Detachment Control 20 E. Kolemen /IAEA/ Oct 2014

Detachment Control in Action Strike Point E. Kolemen / St. Petersburg / Oct 2014 21

X-Point Inner Wall Outer Strike Point CIII Emission – Visible (465 nm) 22 E. Kolemen /IAEA/ Oct 2014

X-Point Inner Wall Outer Strike Point CIII Emission – Visible (465 nm) 23 E. Kolemen /IAEA/ Oct 2014

Partial Detachment Control: Forms a Cold Front in L-mode No Control (#153814) Control (#153816) T e profile Cold front shown in blue eV Control achieves partial detachment • Keep the cold front midway between the X-point and strike point • E. Kolemen / St. Petersburg / Oct 2014 24

Control Stabilized Divertor Temperature (Detachment) but Keeps Core Density Constant 19 Control (#153816) No Control (#153814) 6 x 10 Core Density [m − 3 ] Divertor Density Increases • 4 But Core Density constant • 2 0 Divertor Temperature 1.5 2 2.5 3 3.5 4 • Time [s] reduces to 1 eV 20 Divertor Density [m − 3 ] 2 x 10 1 0 1.5 2 2.5 3 3.5 4 Time [s] Divertor Temperature [eV] control start 20 10 0 1.5 2 2.5 3 3.5 4 Time [s] E. Kolemen / St. Petersburg / Oct 2014 25

Control Stabilized Divertor Temperature (Detachment) but Keeps Core Density Constant 19 Control (#153816) No Control (#153814) 6 x 10 Core Density [m − 3 ] Divertor Density Increases • 4 But Core Density constant • 2 0 Divertor Temperature 1.5 2 2.5 3 3.5 4 • Time [s] reduces to 1 eV 20 Divertor Density [m − 3 ] 2 x 10 1 0 1.5 2 2.5 3 3.5 4 Time [s] Divertor Temperature [eV] control start 20 10 0 1.5 2 2.5 3 3.5 4 Time [s] E. Kolemen / St. Petersburg / Oct 2014 26

Heat Flux Regulation via 1. Snowflake Divertor Control 2. Detachment Control 3. Burn Control with 3D Coils 27 E. Kolemen /IAEA/ Oct 2014

Burn Control: We Need Methods for Faster Control of Fusion Burn Rate Burn: D + T  He + n + 17.6 MeV • ITER concerned with power surges during burning phase and • burn entry/exit conditions Normal methods (heating, density) are slow • – Auxiliary heating control: more heating power capability – cost – Density control is limited: Upper density set by Greenwald limit • Lower density set by detached divertor • – Impurity injection : significant time delays for penetration? 28 E. Kolemen /IAEA/ Oct 2014