H mode characterization in D, H, He / ELM free high confinement regimes (I mode) - CEA
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DE LA RECHERCHE À L’INDUSTRIE H mode characterization in D, H, He / ELM free high confinement regimes (I mode) 23 March 2021 C. Bourdelle, 3rd WEST Planning Meeting Commissariat à l’énergie atomique et aux énergies alternatives - www.cea.fr Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
WEST phase 1 H mode access domain 1/2 In WEST the Bxgrad(B) favorable direction is pointing down, hence in LSN. During phase 1, in 6 pulses (0.5 MA, 3.7 T) a pedestal formation has seen on density, accompanied by a mild increment in WMHD (~20%), a reduction of li, no ELMs, while the flux transported in the SOL was reduced (seen on DI, LP, interferometry in SOL, gas puff reduced) Among these 6 pulses, 2 were in USN, Bxgrad(B) unfavorable, 4 in LSN, hence Bxgrad(B) favorable The 6 transitions occured at similar line averaged density, Psep, and also similar frad
WEST phase 1 H mode access domain 2/2 H mode H mode H mode An oscillatory behaviour between L and H phases is seen, due an increased of Prad once the pedestal forms also reported on Pedestal ch#2 JET-ILW on the D low density branch where frad is larger ~40% [Solano TTF2018] SOL central JET-ILW with majority of T, also larger frad than D [Solano L2H group meeting Feb 2021] AUG far from boronization [Pütterich ITPA 2020] Can be captured with nW as ne^2, and due to density increase, no need for additional W neoclassical inward pinch for example 54719 Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
Outline of proposals - H mode access operational domain, optimized RF scheme - I mode exploration - Role of magnetic configuration on confinement, Er and H mode access - Role of fuelling on confinement, Er and H mode access: LOC-SOC transition, HFS fuelling? Pellets? - Role of frad on H mode access - D vs He impact on confienment and H mdoe access - Pedestal/ ELMs impacted by impurity seeding (LBO, SMBI, GP and powder dropper) Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
Accessing H mode in WEST (C2-W2.5-P4 ) • Proponent(s) : C. Bourdelle, R. Dumont, M. Goniche, J. Morales, L. Vermare, V. Ostuni, P. Manas, J. Hillairet, P. Maget, N. Fedorczak, JF Artaud and all welcome! • Scientific Background & Objectives very likely that only low density transitions. Maybe the power threshold can be drawn below in dashed red. How to access/explore the high density branch? • Experimental Strategy/Machine Constraints and essential diagnostics LHCD operational domain limited: at low density by reflected power and at higher density by lack of central electron heating counter-acting W cooling. ICRH only, applied successfully at 0.7 MA large densities - At 0.5 MA, raise LHCD power from pulses such as ICRH 55564 up to 7MW and increase the density carefully with power. Add as much ICRH power LHCD Once large Ptot, Reduce Ip to 0.4 MA (q95) as min(density) might be shifted -JET-, Pth lower –DIII-D- [Yan] - At 0.7 MA, higher density (55628 ) maximize LHCD ICRH power up to 7MW then add LHCD (coupling already • Nb of sessions / pulses proposed : achieved in such conditions (54962)) ICRH Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
Integrated maximization of the heating power for H-mode operation (C2-W2.3-P33) • Proponent(s) : Ernesto Lerche, Riccardo Ragona , Dirk Van Eester, Tom Wauters, Vincent Maquet et al • Scientific Background & Objectives - Integrate lessons learned in various experiments (building blocks) to maximize input power and minimize core readiation for H-mode operation - Verify if the various techniques developed for combined LH/ICRH ops, gas puffing for ICRH, plasma target for efficient RF heating, etc. are compatible with each other (adjust if necessary) Goals: - Optimized conditions for simultaneous LHCD / ICRH operation (from C2-W2.3-P22) - Best gas injection recipe for good ICRH coupling and minimized RF sheaths (from C2-W2.3-P15) - Robust plasma target (high Ip, high density) but still compatible with efficient LH penetration for core electron heating - Optimized ICRH heating scheme (fundamental H minority at ~5%) with minimal fast particle losses (C2-W2.3-P25) • Experimental Strategy/Machine Constraints and essential diagnostics top view of WEST vessel, indicating the Start with conditions that allow best LH/ICRH operation (defined in C2-W2.3-P22). toroidal position of the 5 radially moveable RF Adjust gas injection for best ICRH coupling and RF-sheath minimization (found in from C2-W2.3- antennas. P15). If not compatible with LHCD, compromise. increase plasma current gradually (400-700kA?). Find best current and increase the power. H concentration scan (2-8%) : compromise between electron heating and fast particle losses Shift by ~1MHz to reduce peak ICRH power density and check if fast particle losses are reduced. • Nb of sessions / pulses proposed : 2/40 Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
I-mode exploration (C2-W2.2-P1 and C2-W2.2-P3) • Proponent(s) : John Rice and Amanda Hubbard (MIT) And Xiao-Lan Zou, M. Goniche, L. Vermare, F. Clairet, P. Manz, A.D. Liu, E.Z. Li, L. Wang, J. Morales • Scientific Background & Objectives WEST, 55562, density rises… verify the operating window between I- and H-mode at 3.8T Within ITPA TC-19 and WPTE I-mode • Experimental Strategy/Machine Constraints and essential diagnostics operate with 'unfavorable' ion BxgradB drift, hence in USN at max B From [Manz NF2020] there might an optimum nsep value Need to see pedestal on T and not on density. Thomson scattering needed. No simple signature in the D_alpha emission. [Hubbard NF2016] Appearance of a weakly coherent mode of edge fluctuations with a frequency in the 100-200 kHz range on Cmod and on EAST low-frequency coherent mode of 6−12 kHz corresponds to a radially localized edge temperature ring oscillation (ETRO) (m=0, n=0). Need reflectometry • Nb of sessions / pulses proposed : diags. 1 session to establish I mode and 2 for Once established: investigate the magnetic field dependence of the operational window, so a parameter scan range of magnetic fields from minimum to maximum will be requested. The final aspect is to explore the parameter dependences of the energy confinement and I- WP TE : 1 session in 2021 RT08 mode threshold power, which will require current, density and input power scans. Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
Multi-machine experiments on radial electric field in “favorable” versus “unfavorable” configuration (C2-W2.7-P3) • Proponent(s) : Laure Vermare Jamie Gunn Pascale Hennequin Garrard Conway Ulrike Plank Laurie Porte Stefano Coda Nicolas Fedorczak Gloria Falchetto Hugo Bufferand • Scientific Background & Objectives Er shear is a key player for the turbulence quench and subsequent pedestal formation. Studying its profile might enlighten on the operational domain for easier H mode access Goals: - Measure and compare the Er profiles at the edge in LSN, USN and DN configurations - Explore the response of these Er profiles changing plasma current Compare WEST/AUG/TCV within WPTE VExB reaches -11.2km/s • Experimental Strategy/Machine Constraints and essential diagnostics The deepest radial electric field well has been Choose plasma conditions adapted to DBS measurement location (at the edge) For each observed in USN configuration, here 55563 (similar in machine, when comparable plasmas (in term of Ip, ne, Power) are obtained in the three 55562), Doppler BackScattering configurations => perform Ip scan in all configurations. If, no comparable plasmas are accessible in the three different configurations, choose the most adapted in term of DBS accessibility for each configuration and perform the Ip scan in each set of plasma conditions, • Nb of sessions / pulses proposed : then only relative variations will be studied. Langmuir probes and DBS are essential WP TE ~1 session (RT01) in 2021 Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
Sources of the radial electric fields (C2-W2.7-P2 ) • Proponent(s) : Laure Vermare • Scientific Background & Objectives The understanding of the formation of the radial profile of the radial electric field :magnetic ripple, edge physics and turbulence will be investigated trough several experiments. In MAST the H mode is more easily accessed in DN, on WEST large differences on the Er well are reported btw LSN/USN… Goals: - Measure and compare the Er profiles at the edge in LSN, USN and DN configurations - Explore the response of these Er profiles changing plasma current, magnetic configuration, etc • Experimental Strategy/Machine Constraints and essential diagnostics illustration of the go from LSN to USN passing by an equilibrate DN. From ohmic to several additional power ( link with magnetic C2-W2.5-P1) configurations In USN and LSN: Scan on the vertical position of the plasma center and Rext; to impact local ripple accessible in WEST trapping in ohmic B=3.7T Same power but ICRH versus LHCD at (3-4MW), in USN and LSN: impact of fast particle losses due to ripple • Nb of sessions / pulses proposed : Change the level of neutral at the edge (see C2-W2.5-P1) B scan, keeping Ip constant, to separate the effect of q from Ip, in ohmic 3/45 And ramp up the density at various Ip to study the LOC-SOC transition (C2-W2.7-P5, R. Sabot) Langmuir probes and DBS are essential Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
impact of magnetic configuration, fuelling and heating (C2-W2.5-P1) search for the best configuration that minimizes the radiating power (C2-W2.5-P2) • Proponent(s) : Gh. Antar, P. Devynck • Scientific Background & Objectives Reduce the power threshold: explore the impact of the magnetic configuration and of the fueling localisation • Experimental Strategy/Machine Constraints and essential diagnostics - move the plasma from the lower single null configuration to the upper null configuration, passing by double null : - monitor frad in LHCD heated plasmas in these configurations (link with proposal - Fuel by HFS using pellet pipes, and use SMBI Note that In MAST HFS fueling favoured H mode access [Counsell PPCF2002] [Antar PPCF20026] MAST ohmic H mode easier if |inter separatrix separation / ri | < 0.5 • Nb of sessions / pulses proposed : 10+10 pulses Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
Explore pellet enhanced confinement regimes (C2-W2.7-P1 ) • Proponent(s) : MJ Pueschel (DIFFER) • Scientific Background & Objectives In certain stellarator configurationspellet injection can lead to an enhanced-confinement state. A number of conditions are thought to be beneficial for this mechanism: short connection lengths, large aspect ratio, negative shear, and curvature de-alignment from trapping regions. • Experimental Strategy/Machine Constraints and essential diagnostics - conduct pellet-injection studies, - both during an early phase in the discharge when the q profile exhibits a lower slope and during the standard L-mode confinement phase. - determine how energy confinement is affected by this change in density profile. [Baldzuhn PPCF2020] W7X Improved conft after pellet injection • Nb of sessions / pulses proposed : 1 session Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
Impact of the fraction of radiated power on H mode access C2-W2.5-P3 • Proponent(s) : C. Bourdelle, P. Devynck • Scientific Background & Objectives On WEST, for an identical power crossing the separatrix, we can either enter in H mode or stay in L mode Is there a threshold in terms of frad to access H mode? (link with C2-W2.5-P2) In WEST/AUG/JET with large frad oscillatory transitions L-H-L etc. Highly relevant for near threshold operation in ITER (ITPA-IOS activity) • Experimental Strategy/Machine Constraints and essential diagnostics The fraction of radiated power due to W content will be varied by - repeating the same power ramp just after and far from a boronization - reducing the gas fueling (if it is shown to impact the fraction of radiated power on WEST with the 10 pumps active for the 1st time in C6) during the power ramp. - Changing the magnetic configuration, incl DN (C2-W2.5-P2) the impact of lighter impurities such as N/Ne/Ar/Kr will be explored by seeding in • Nb of sessions / pulses proposed : feedforward various levels of impurities while ramping up the power, similarly to 2/27 what has been done in JET [Maggi ITPA 2016] WP TE : no session in 2021 Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
Helium and deuterium plasmas comparison (C2-W2.5-P5) • Proponent(s) : J. Morales • Scientific Background & Objectives In view of ITER non nuclear phase, He H mode access and confinement are very important. ITPA activities. WEST specificities: Same level of additional heating in D and He (ICRH H min and LHCD) Turbo-pumping, similar for D and He thus allowing, in principle, a similar span in plasma H-mode divertor recycling conditions Goals: Compare L to H mode power threshold in He and D Compare He type I ELMy H mode with a D pair at: same power across the separatrix, at the same distance of the L-H power threshold • Experimental Strategy/Machine Constraints and essential diagnostics Start from a known D plasma with a clear L-H transition, then: He concentration scan at fixed [Gohil ITPA 2015] density. Increase injected power, perform density scan DIII-D results If type III ELMy H mode found, try to get threshold between type III and type I ELMy H mode: Helium type I ELMy H-mode and L mode confinement compared to D plasmas: Power scan at fixed density (similar to existing D scans if possible) with high He concentration Density scan at fixed power (similar to existing D scans if possible) with high He concentration • Nb of sessions / pulses proposed : 3- 4/50-70 Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
Impact of seeded impurities on pedestal instabilities and the related transport (C2-W2.5-P6) and (C2-W2.2-P2) • Proponent(s) : Guoliang XIAO (xiaogl@swip.ac.cn), Tianbo Wang, Mingkun Han, Yiren Zhu and Xiaolan Zou (C2- W2.5-P6) And A.Diallo (adiallo@pppl.gov), P. Moreau, G. Bodner, A. Bortolon, R. Lunsford, R. Maingi, A. Nagy, S. Zhen, P. Lotte, Z. Unterberg, C. Klepper, D. Donovan, D. Currelli, E. Tsitrone, C. Bourdelle et al. (C2- W2.2-P2) • Scientific Background & Objectives Based on the result on HL-2A and EAST, the impact of impurities on pedestal instabilities / ELM suppression and the underlying transport in the full W device The main objectives are listed as follows. Exciting the electromagnetic instabilities by impurity seeding to study the optimal condition to minimize the impurity accumulation and for an edge peaked impurity profile The effect of the impurity seeding on pedestal behavior Mitigate or suppress ELMs by impurity seeding Experimental Strategy/Machine Constraints and essential diagnostics Identify an ELMing regime in LSN/USN and/or DN [Y.P. Zhang NF 2016] HL-2A - Scan (N2, Ne, Ar) by GP, SMBI in ELMy H-mode plasmas (C2-W2.5-P6) - Scan the IPD drop rate to observe ELM stabilization (C2-W2.2-P2) • Nb of sessions / pulses proposed : 3- THIS PROPOSAL REQUIRES fast reflectometry, DBS, and Thomson scattering and… ELMy H modes 4/35-40 Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
DE LA RECHERCHE À L’INDUSTRIE backups Commissariat à l’énergie atomique et aux énergies alternatives - www.cea.fr Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
Not much diffrence btw LSN and USN transitions No I mode? Density in pedestal modified in USN transition, less than in LSN, but still... Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
The result of a very narrow operationnal domain with LHCD Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
- Applying a factor 2 on Te in C5 (tbc), nice overlap C4 and C5 stabl e/ unsta stable / cold ble hot core core To be on the safe side, need to have Te(0 Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
How does look an L to H transition at JET? Far from being clear When working near power threshold W_MHD x 2 this is only for P ~ 2x P_th… ‘mushier’ on low density branch. Are we on the low density branch? In WEST we are at most just slightly above thresold, so it is normal to see « mushy » transitions Moreover… Commissariat à l’énergie atomique et aux énergies alternatives Here Frad much higher than here E. Tsitrone and TFL COEX February 11 2021
L-H transition with T, H in JET-ILW. More T, less easy transition… L-H transition with more T Prad increase in H mode and Te decrease! As in WEST! Due to larger W sputtering with T?? Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
METIS interpretative modelling of the radiation oscillating phases of 54719, with: ∝ 2 vs TOFU synthetic diagnostics SXR and bolometer W shape cW offset cW /MW of cW /MW of imp1 imp2 LH ICRH ∝ 2 1e-5 0.5e-5 0.5e-5 7 8 Commissariat à l’énergie atomique et aux énergies alternatives E. Tsitrone and TFL COEX February 11 2021
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