Emanuele Poli, 17 th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012 Assessment of ECCD-Assisted Assessment of ECCD-Assisted Operation Operation in DEMO in DEMO Emanuele Poli 1 , Emiliano Fable 1 , Giovanni Tardini 1 , Hartmut Zohm 1 , Daniela Farina 2 , Lorenzo Figini 2 , Nikolai Marushchenko 3 , Laurie Porte 4 (1) Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching bei München, Germany (2) Istituto di Fisica del Plasma del CNR, EURATOM-ENEA-CNR Association, Milano, Italy (3) Max-Planck-Institut für Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, Germany (4) Centre de Recherches en Physique des Plasmas, CRPP-EPFL, Lausanne, Switzerland Max-Planck- Insititut für Plasmaphysik
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Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Assessment of ECCD-Assisted Operation Assessment of ECCD-Assisted Operation in DEMOin DEMO
Emanuele Poli1, Emiliano Fable1, Giovanni Tardini1, Hartmut Zohm1, Daniela Farina2, Lorenzo Figini2, Nikolai Marushchenko3, Laurie Porte4
(1) Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching bei München, Germany(2) Istituto di Fisica del Plasma del CNR, EURATOM-ENEA-CNR Association, Milano, Italy(3) Max-Planck-Institut für Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, Germany(4) Centre de Recherches en Physique des Plasmas, CRPP-EPFL, Lausanne, Switzerland
Max-Planck-Insititut für Plasmaphysik
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Motivations External current drive essential in a tokamak fusion reactor to ensure (nearly) steady-state operation
ECCD usually considered technologically mature, but not very attractive because of comparatively low CD efficiency (driven current per injected power)
However: • Wall-plug efficiency also important for a power plant (might be higher for ECCD)• Smaller slot in the blanket required for ECCD as compared to NBI• Optimization of ECCD efficiency still possible…
In this talk:• Exploration of the achievable ECCD efficiency for 2 DEMO options• First estimate of the ECCD power required for fully non-inductive operation (loop voltage → 0)
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Current drive efficiency “Standard” efficiency used for reactor studies:
Typical values quoted for reactor-grade plasmas:
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
DEMO models Global parameters as originally proposed by D. Ward for H & CD assessment CHEASE equilibria reprocessed by ASTRA (investigate different density and temperature profiles at same βN) Steady-state DEMO: R0 = 8.5 m, a = 2.83 m, B0 = 5.84 T, βN = 2.95
Density Temperature
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
DEMO models Global parameters as originally proposed by D. Ward for H & CD assessment CHEASE equilibria reprocessed by ASTRA (investigate different density and temperature profiles at same βN) Pulsed (6 hrs) DEMO: R0 = 9.6 m, a = 2.4 m, B0 = 7.45 T, βN = 2.6
Density Temperature
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Current drive scenarios High magnetic field → ordinary mode, first-harmonic heating envisaged
High temperature → significant parasitic absorption by higher harmonics
Resonance condition
implies first-harmonic absorption possible if
ECCD modelling (TORBEAM) including momentum conservation (Marushchenko)
First-harmonic accessibility (Steady-State DEMO)
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Mid-plane injection, peaked density Scan over frequency ω/2π and toroidal angle β (poloidal angle = 0) ICD first rises as the deposition is pushed towards the plasma centre, then decreases because of too large parasitic absorption High-field side hardly accessible
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Mid-plane injection, peaked density Scan over frequency ω/2π and toroidal angle β (poloidal angle = 0) ICD first rises as the deposition is pushed towards the plasma centre, then decreases because of too large parasitic absorption High-field side hardly accessible
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Mid-plane injection: example Near maximum current drive: β = 40°, ω/2π = 215 GHz Second-harmonic absorption ≈ 8% (34% for ω/2π=225 GHz, 28% for β=35°)
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Top injection, peaked density, 230 GHz Injection from R = 10.5 m, Z = 3.5 m to reduce the path through the 2nd-harmonic absorption region Allows high-efficiency off-axis current High N|| needed to move the 1st -harmonic region to larger R; more sensitive to injection angle
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Top injection, peaked density Optimum efficiency shifts towards larger minor radii for higher antenna location γCD > 0.35 obtained around ρpol ~ 0.2-0.3
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Top injection, flat density, 230 GHz Injection from R = 10.5 m, Z = 3.5 m Higher ECCD current because of lower density as in the “peaked” case, but lower efficiency
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Large-aspect-ratio, pulsed DEMO
Lower trapped-particle fraction, lower Zeff → higher current drive High frequencies needed because of high magnetic field (290 GHz in this example)
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Power required for steady state
Vanishing loop voltage achieved for deposition around ρpol = 0.4 with approx. 230 MW of injected power (bootstrap fraction around 0.35)
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Summary
High ECCD efficiency possible with careful optimization (largest values around ρpol ~ 0.3) High-frequency sources necessary
Investigation of self-consistent ECCD-equilibrium loop under way → optimization of CD position in terms of efficiency and bootstrap fraction
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Current drive efficiencies CD efficiency defined on each flux surface as ratio between current density and deposited power density
Dimensionless efficiency
In terms of total driven current and total absorbed power
(apart from geometric factors)
ζCD intended to describe efficiency variations due to changes of the velocity-space region where the wave-particle interaction takes place
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
ECCD Modelling Beam tracing code TORBEAM, linear absorption (TORAY and GRAY fully-relativistic routines), adjoint method for CD (including momentum conservation) Extensively benchmarked… Momentum conservation leads to a CD increase
Emanuele Poli, 17th Joint Workshop on ECE and ECRH Deurne, May 7-10, 2012
Mid-plane injection, peaked density Scan over frequency ω/2π and toroidal angle β (poloidal angle = 0) ICD first rises as the deposition is pushed towards the plasma centre, then decreases because of too large parasitic absorption ζCD ~ γCD/Te increases due decreasing trapped-particle fraction
