FAST 1 : a Physics and Technology Experiment on the Fusion Road Map

Transcription

1 Fusion Advanced Studies Torus FAST 1 : a Physics and Technology Experiment on the Fusion Road Map Presented by A. A. Tuccillo on behalf of ENEA-Euratom Association Univ. of Rome Tor Vergata Univ. of Catania 1 Pizzuto A. et al Nucl. Fusion (2010) SIF- Napoli - 21/09/2012 Angelo A. Tuccillo

2 SCOPE OF THE FAST PROPOSAL A Satellite Experiment finalized to support ITER and early DEMO design Complementary, with some overlap, to JT60-SA. Designed to study in an integrated experiment: Plasma Wall Interaction (Power Exhaust, Divertor - First Wall, Liquid Metals, Materials ) Plasma Operation (ELMs, Plasma Controls, Heating coupling ) Burning Plasma (Fast Particles driven Instabilities ) Here we focus on some of the physics aspects Technical issues will be only marginally addressed 2

3 Kadomtsev Similarity Argument The Bulk Plasma physics can be characterized by three dimensionless parameters: ρ*, β and ν* [Kadomtsev 75] Alternative engineering parameters [Lackner 90]: nr 2, BR 5/4 and TR 1/2, with R free to vary Plasma edge, (where atomic physics is important), is not preserved by above parameters ρ*, β and ν*. For scaling an Integrated Burning Plasmas Experiment a fourth parameter must be introduced: T [Lackner 94, Catto 96] Using the collection of ρ*, β and ν* and T, on the other hand, makes it impossible to define a non-trivial set of similarity experiments [Lackner 98] 3

4 Kadomtsev Argument Revisited By using a weak 1 similarity argument it is possible a suitable rescaling of ITER parameters, still addressing the relevant integrated physics This can be done assuming ρ*r ε, β, τ SD /τ E are fixed to the ITER one (in FAST ε = 1/2 is assumed) The choice of relaxing ρ* scaling is motivated by: Cross-scale coupling (micro-meso scales) is preserved for ρ* H /ρ* set by T H /T given by condition of dominant electron heating (~70% as fusion alphas in ITER) Relaxing β scaling would imply relaxing the frequency ordering of meso- to micro-scale fluctuation spectra + preserving profiles 4

5 Motivation for choosing ε = 1/2 in ρ*r ε = 0 admits only the trivial solution or unrealistic behaviour for the temperature: T R -1/3 Since T R -2/3 R 2ε ; for 1/3 we get always an unrealistic scaling for T Thus = 1/2 (FAST), is an heuristic but reasonable choice (weak changes around this value); it makes * as close as possible to ITER relevant values The choice =1, i.e. a much less stringent and severe than that of FAST; it would yield the weak similarity scaling fitting important examples of present day machines, like JET and ASDEX Upgrade; for instance we would get: a) For ASDEX B=2.2 T ; Ip=1.65 MA ; T=3.4 KeV ; Q = b) For JET B=3.3 T ; Ip=4.50 MA ; T=7.6 KeV ; Q =

6 Kadomtsev Argument Revisited Using R as free parameter the obtained scalings are T R 1/3, I p R 2/3, B R -1/3, τ R 3/2, P ADD /R R -1/6, Cost R 7/3 Given a plasma radius R it is possible selecting the parameters to perform a similarity experiment to ITER H-mode scenario. R(m)" T(keV)" B(T)" I p (MA)" n(10 20 m -3 )" P(MW)" t AT (s)" Cost(M )" Q" 1.82" 13" 7.5" 6.5" 2" 30" 170" 300".65" 2.4" 14" 6.8" 7.8" 1.5" 38" 260" 1.9!.85" 3.0" 15" 6.3" 9.1" 1.2" 45" 360" 3.2! 1.1" Of course plasma radius defines machine performance, consequently a compromise has to be made between Cost and Performance 6

7 FAST: an Integrated Experiment (scal ed) The ITER magnetic Topology (plasma shape) is guaranteed, for any Plasma Scenarios, by using the Extreme Shape Controller SIF- Napoli - 21/09/2012 Plasma Current (MA) BT (T) Major Radius (m) Minor Radius (m) Elongation k95 Triangularity δ95 Safety Factor q95 Vp (m3) <n>(m-3 ) Flat-top BT (s) H&CD power (MW) ICRH ECRH LH NNBI P/R (MW/m) Q Angelo A. Tuccillo 8 (10) ~ 3 (2.3) x > (->15) 4 (->15) 6 10 (20)? 22 ~ 1.5 (3) 7

8 Reference Scenario 2 Calabro G. et al Nucl. Fusion (2008) All ITER scenarios are possible in FAST 2 The so called Reference Scenario is finalized to study in an integrated way and in a reliable discharge Plasma Wall Interaction (Wall Load, W Divertor and First Wall, different Materials and divertor solutions, liquid metals ) Plasma Operation (ELMs, Plasma Controls, Heating coupling ) Burning Plasma Problems (Fast Particles driven Instabilities ) H&CD power (MW) 40 ICRH 30 ECRH 4 LH 6 NNBI 10? 8

9 Criticality W pollution, due to the ICRH induced Sputtering (see the AUG results). To care for this problem we are following two different routes: 1. Increase the Operational Space Flexibility 2. Optimize the Antenna Design è To be tested in AUG Doubts about handling 30MW ICRH in a small Plasma Volume C-MOD: 5-6 MW ICRH in 1 m 3 à 5 MW/m 3 FAST: 30 MW ICRH in 23 m 3 à 1.7 MW/m 3 Antenna mouth Power density P s 5-7MW/m 2 9

10 Increasing Machine Flexibility H-mode H-mode FAST reference ECRH I p (MA) q B T (T) (6.7) H <n 20 > (m -3 ) 2 2 P th_h (MW) β N τ E (s) τ res (s) T 0 (kev) Q t discharge (s) t flat-top (s) I NI /I p (%) P ADD (MW) Additional scenarios are being developed to increase machine flexibility thus mitigating risk from W sputtering Only ~15 MW are necessary to generate the appropriate Fast particle population while 30MW are necessary for the scenario Working with B T = T it would be possible using 15 MW of ECRH at 170 GHz and 15 MW of ICRH 10

11 MW ICRH + 15MW ECRH Te - ICRH Te - ICRH Te - (ICRH) Te - ICRH Te - (ECRH+ICRH) Te - (ECRH+ICRH) Te - (ECRH+ICRH) Te - (ECRH+ICRH) Ti - (ECRH+ICRH) Ti - (ECRH+ICRH) Ti - (ECRH+ICRH) Ti - (ECRH+ICRH) Ti- ICRH Ti - ICRH Ti - (ICRH) Ti - ICRH T (ev) BgB T (ev) Weiland GLF23 GCM ρ ρ T i and T e profiles as predicted by using different transport models T e always larger of T i (Specially with ICRH+ECRH) a) power flowing to electrons always larger than that to ions b) ITG threshold decreases since T e /T i increases ρ 11 ρ Calabrò, Mantica et al.. IAEA 2010THC/P2-05

12 Advanced Scenarios Three different scenarios proposed for Advanced Tokamak Studies In all of them a slightly reverse q profile and an improved H 98 (=1.5) is assumed Recent Experimental and Heuristic results show the necessity of a toroidal rotation to get an Internal Transport Barrier (ITB) 12

13 From the scaling proposed by Alcator C_MOD (a compact machine too) we have assumed an edge rotation =30 krad/s Using the most recent theory results for the velocity inward pinch (Prandtl number Pr= / i =1 and pinch number Rv / ~4) we can evaluate the intrinsic rotation profile a complete simulation has been performed for the full NICD scenario by using the transport model Bohm-gyroBohm ω φ (rad/s) Advanced Scenarios n e V Φ n e (m -3 ) T (ev) TI no rotation TI rotation TE no rotation TE rotation ρ Calabrò, Mantica et al. IAEA 2010 THC/P ρ 13

14 NNBI System MeV NNBI system, injected at 45 on the magnetic axis. planned on a second phase NBI Fast Particles (m-3) 1018 ρ SIF- Napoli - 21/09/2012 The system has the capability to inject from on axis to half radius. This flexibility, together with the different fast particle anisotropy, will allow to better match the dynamics of the alpha particle on ITER. Angelo A. Tuccillo 14

15 ICRH + NNBI β H_perp β H_par - NNBI NNBI=10MW; ICRH=30MW f=78mhz; He=2% BgB + rot GLF ρ 1 NNBI=10MW - E=1MeV ICRH=30MW 0.05 BgB + rot GLF ρ NNBI system provides a momentum input. By using ASCOT and JETTO a transport simulation has been performed, with and without rotation, with 10 MW NNBI and 30 MW ICRH On the extreme scenario at 8MA and <n>~ m -3 HMGC code - 8MA scenario Effect of n=8 and n=16 saturated EPM on the H radial profile. IAEA 2010: Wang et al. THW/2 4Ra Calabrò, Mantica et al, THC/P2-05; Cardinali, et al. THW P

16 FAST Snow Flakes Configuration A Snow Flakes Divertor (SFD) configuration realized by using only external standard shaping coils. Obtained a Flux Expansion, up to a factor 5 larger than the Standard Divertor (SD), with a correspondent strong decrease of the Power Flux. Standard X point FAST magnetic configuration SIF- Napoli - 21/09/2012 FAST Snow Flake magnetic configuration Angelo A. Tuccillo Flux Expansion SD SFD fm ~4 ~20 So far obtained a full scenario (low and high βp) at Ip=6.5MA, lasting ~ 20s 16

17 Divertor for Snow Flakes A new divertor has been designed to be compatible with the standard X point configuration and the Snow Flakes. Machine bottom part has to be ri-designed to be compatible with different divertor geometries and accounts for RH 17

18 In summary FAST FAST is flexible and integrates many physics issues, so far never addressed or only separately addressed Is an ideal test bed to exploit advanced divertor anf FW materials and configurations (W, Liquid Lithium) suitable for tackling the power exhaust problem in view of DEMO Can provide a unique opportunity to explore unexpected physics issues thus helping in avoiding long and costly scenario development in ITER FAST is intrinsically multi-dimensional à ideal for nonlinear physics with many time scales and threshold phenomena Can be a key facility for international collaboration, training of young scientists in a ITER-class device for integrated physics and development of new diagnostics FAST and JT60-SA, being complementary satellites, can serve as strong and thorough basis to support ITER and to address/tackle some DEMO problem. 18