Browsing by Author "Carvalho, I. S."

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Characterisation of divertor detachment onset in JET-ILW hydrogen, deuterium, tritium and deuterium–tritium low-confinement mode plasmas
(2023-03) Groth, M.; Solokha, V.; Aleiferis, S.; Brezinsek, S.; Brix, M.; Carvalho, I. S.; Carvalho, P.; Corrigan, G.; Harting, D.; Horsten, N.; Jepu, I.; Karhunen, J.; Kirov, K.; Lomanowski, B.; Lawson, K. D.; Lowry, C.; Meigs, A. G.; Menmuir, S.; Pawelec, E.; Pereira, T.; Shaw, A.; Silburn, S.; Thomas, B.; Wiesen, S.; Börner, P.; Borodin, D.; Jachmich, S.; Reiter, D.; Sergienko, G.; Stancar, Z.; Viola, B.; Beaumont, P.; Bernardo, J.; Coffey, I.; Conway, N. J.; de la Luna, E.; Douai, D.; Giroud, C.; Hillesheim, J.; Horvath, L.; Huber, A.; Lomas, P.; Maggi, C. F.; Maslov, M.; Perez von Thun, C.; Scully, S.; Vianello, N.; Wischmeier, M.; , JET Contributors
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Measurements of the ion currents to and plasma conditions at the low-field side (LFS) divertor target plate in low-confinement mode plasmas in the JET ITER-like wall materials configuration show that the core plasma density required to detach the LFS divertor plasma is independent of the hydrogenic species protium, deuterium and tritium, and a 40 %/60 % deuterium–tritium mixture. This observation applies to a divertor plasma configuration with the LFS strike line connected to the horizontal part of the LFS divertor chosen because of its superior diagnostic coverage. The finding is independent of the operational status of the JET cryogenic pump. The electron temperature (Te) at the LFS strike line was markedly reduced from 25 eV to 5 eV over a narrow range of increasing core plasma density, and observed to be between 2 eV and 3 eV at the onset of detachment. The electron density (ne) peaks across the LFS plasma when Te at the target plate is 1 eV, and spatially moves to the X-point for higher core densities. The density limit was found approximately 20 % higher in protium than in tritium and deuterium–tritium plasmas.
Characterization of detachment inferred from the Balmer line ratios in JET-ILW low-confinement mode plasmas
(2025-03) Rikala, Vesa Pekka; Groth, M.; Meigs, A. G.; Reiter, D.; Lomanowski, B.; Shaw, A.; Aleiferis, S.; Corrigan, G.; Carvalho, I. S.; Harting, D.; Horsten, N.; Jepu, I.; Karhunen, J.; Lawson, K. D.; Lowry, C.; Menmuir, S.; Thomas, B.; Borodin, D.; Douai, D.; Huber, A.; , JET Contributors
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Spectroscopic measurements of the hydrogenic Balmer-α and Balmer-γ line emission in JET-ILW low-confinement mode (L-mode) deuterium plasmas are used to assess the onset of volume recombination in the low-field side (LFS) divertor. The evolution of the EDGE2D-EIRENE predicted Balmer-γ to Balmer-α emission ratio from low-recycling to detached conditions is in qualitative agreement with the measured ratio. In low-recycling conditions the EDGE2D-EIRENE predicted line-emission is within 30% of measured emission, in high-recycling within 20%t, and in detached conditions lower by a factor of 2.5.
The core-edge integrated neon-seeded scenario in deuterium-tritium at JET
(2024-10) Giroud, C.; Carvalho, I. S.; Brezinsek, S.; Huber, A.; Keeling, D.; Mailloux, J.; Pitts, R. A.; Lerche, E.; Henriques, R.; Hillesheim, J.; Lawson, K.; Marin, M.; Pawelec, E.; Sos, M.; Sun, H. J.; Tomes, M.; Aleiferis, S.; Bleasdale, A.; Brix, M.; Boboc, A.; Bernardo, J.; Carvalho, P.; Coffey, I.; Henderson, S.; King, D. B.; Rimini, F.; Maslov, M.; Alessi, E.; Craciunescu, T.; Fontana, M.; Fontdecaba, J. M.; Garzotti, L.; Ghani, Z.; Horvath, L.; Jepu, I.; Karhunen, J.; Kos, D.; Litherland-Smith, E.; Meigs, A.; Menmuir, S.; Morales, R. B.; Nowak, S.; Peluso, E.; Pereira, T.; Parail, V.; Petravich, G.; Pucella, G.; Puglia, P.; Refy, D.; Scully, S.; , JET Contributors
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This paper reports the first experiment carried out in deuterium-tritium addressing the integration of a radiative divertor for heat-load control with good confinement. Neon seeding was carried out for the first time in a D-T plasma as part of the second D-T campaign of JET with its Be/W wall environment. The technical difficulties linked to the re-ionisation heat load are reported in T and D-T. This paper compares the impact of neon seeding on D-T plasmas and their D counterpart on the divertor detachment, localisation of the radiation, scrape-off profiles, pedestal structure, edge localised modes and global confinement.
Experimental study on the role of the target electron temperature as a key parameter linking recycling to plasma performance in JET-ILW
(2022-06) Lomanowski, B.; Dunne, M.; Vianello, N.; Aleiferis, S.; Brix, M.; Canik, J.; Carvalho, I. S.; Frassinetti, L.; Frigione, D.; Garzotti, L.; Groth, M.; Meigs, A.; Menmuir, S.; Maslov, M.; Pereira, T.; Perez Von Thun, C.; Reinke, M.; Refy, D.; Rimini, F.; Rubino, G.; Schneider, P. A.; Sergienko, G.; Uccello, A.; Van Eester, D.; , JET Contributors
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Changes in global and edge plasma parameters (H98(y,2), dimensionless collisionality ν*, core density peaking, separatrix density ne,sep) with variations in the D2 fueling rate and divertor configuration are unified into a single trend when mapped to ⟨Te,ot⟩, the spatially averaged spectroscopically derived outer target electron temperature. Dedicated JET with the ITER-like wall (JET-ILW) experiments in combination with an extended JET-ILW database of unseeded low-triangularity H-mode plasmas spanning a wide range of D2 fueling rates, Ip, Bt and heating power have demonstrated the importance of ⟨Te,ot⟩ as a key physics parameter linking the recycling particle source and detachment with plasma performance. The remarkably robust H98(y,2) trend with ⟨Te,ot⟩ is connected to a strong inverse correlation between ⟨Te,ot⟩, ne,sep and ν*, thus directly linking changes in the divertor recycling moderated by ⟨Te,ot⟩ with the previously established relationship between ν*, core density peaking and core pressure resulting in a degradation in core plasma performance with decreasing ⟨Te,ot⟩ (increasing ν*). A strong inverse correlation between the separatrix to pedestal density ratio, ne,sep/ne,ped, and ⟨Te,ot⟩ is also established, with the rise in ne,sep/ne,ped saturating at ⟨Te,ot⟩ > 10 eV. A strong reduction in H98(y,2) is observed as ⟨Te,ot⟩ is driven from 30 to 10 eV via additional D2 gas fueling, while the divertor remains attached. Consequently, the pronounced performance degradation in attached divertor conditions has implications for impurity seeding radiative divertor scenarios, in which H98(y,2) is already low (∼0.7) before impurities are injected into the plasma since moderate gas fueling rates are required to promote high divertor neutral pressure. A favorable pedestal pressure, pe,ped, dependence on Ip has also been observed, with an overall increase in pe,ped at Ip = 3.4 MA as ⟨Te,ot⟩ is driven down from attached to high-recycling divertor conditions. In contrast, pe,ped is reduced with decreasing ⟨Te,ot⟩ in the lower Ip branches. Further work is needed to (i) clarify the potential role of edge opacity on the observed favorable pedestal pressure Ip scaling; as well as to (ii) project the global and edge plasma performance trends with ⟨Te,ot⟩ to reactor-scale devices to improve predictive capability of the coupling between recycling and confined plasma fueling in what are foreseen to be more opaque edge plasma conditions.
Investigation of H-mode density limit in mixed protium–deuterium plasmas at JET with ITER-like wall
(2024-12) Huber, A.; Sergienko, G.; Groth, M.; Keeling, D.; Wischmeier, M.; Douai, D.; Lerche, E.; Perez von Thun, C.; Brezinsek, S.; Huber, V.; Boboc, A.; Brix, M.; Carvalho, I. S.; Chankin, A. V.; Delabie, E.; Jepu, I.; Kachkanov, V.; Kiptily, V.; Kirov, K.; Linsmeier, Ch; Litherland-Smith, E.; Lowry, C. G.; Maggi, C. F.; Mailloux, J.; Meigs, A. G.; Mertens, Ph; Poradzinski, M.; Zastrow, K. D.; Zlobinski, M.; , JET Contributors; , The EUROfusion Tokamak Exploitation Team
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Analysis of comparable discharges fuelled by either deuterium or protium reveals a clear relationship between the isotope mass and the H-mode density limit. Notably, the density limit is significantly lower in protium, showing a reduction of up to 35 % compared to identical deuterium plasma conditions. Within mixed H-mode density limit (HDL) plasmas, the maximum achievable density, or H-mode density limit, decreases with increasing protium concentration, denoted as cH. For instance, the highest corresponding maximum Greenwald fraction (fGW) of about 1.02 was observed in the pulse with the lowest cH value of 4.4 %. This fGW decreases to 0.96 at cH = 48 %. The average atomic mass, A¯, of the plasma species decreases in these pulses from the value of 1.96 (cH = 4.4 %) down to 1.52 (cH = 48 %). Interestingly, the maximum achievable density appears to be largely unaffected by the applied power value, regardless of whether deuterium or protium is used, as well as under mixed H/D fuelling conditions. Additionally, the measured Greenwald fractions are agreed with a heuristic model based on the SOL pressure threshold of an MHD instability, as proposed by Goldston. This comparison, especially concerning the model's dependence on isotopic mass, shows full consistency between the measured and predicted Greenwald fractions.
Isotope mass scaling and transport comparison between JET Deuterium and Tritium L-mode plasmas
(2023-11) Tala, T.; Järvinen, A. E.; Maggi, C. F.; Mantica, P.; Mariani, A.; Salmi, A.; Carvalho, I. S.; Chomiczewska, A.; Delabie, E.; Devasagayam, F.; Ferreira, J.; Gromelski, W.; Hawkes, N.; Horvath, L.; Karhunen, J.; King, D.; Kirjasuo, A.; Kowalska-Strzeciwilk, E.; Leerink, S.; Lennholm, M.; Lomanowski, B.; Maslov, M.; Menmuir, S.; Morales, R. B.; Sharma, R.; Sun, H.; Tanaka, K.; , JET Contributors
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The dimensionless isotope mass scaling experiment between pure Deuterium and pure Tritium plasmas with matched ρ ∗ , ν ∗ , β n , q and T e / T i has been achieved in JET L-mode with dominant electron heating (NBI+ohmic) conditions. 28% higher scaled energy confinement time B t τ E , t h / A is found in favour of the Tritium plasma. This can be cast in the form of the dimensionless energy confinement scaling law as Ω i τ E , t h ∼ A 0.48 ± 0.16 . This significant isotope mass scaling is consequently seen in the scaled one-fluid heat diffusion coefficient A χ e f f / B t which is around 50% lower in the Tritium plasma throughout the whole plasma radius. The isotope mass dependence in the particle transport channel is negligible, supported also by the perturbative particle transport analysis with gas puff modulation. The comparison of the edge particle fuelling or ionisation profiles from the EDGE2D-EIRENE simulations show that the absolute density differences that are necessary for the dimensionless match in the confined plasma dominate over any isotope mass dependencies of particle fuelling and ionization profiles at the plasma edge. Local GENE simulation results indicate a mild anti-gyroBohm effect at ρ t o r = 0.6 and thereby a small isotope mass dependence in favour of Tritium on heat transport and a negligible effect on particle transport. A significant fraction of the isotope scaling and reduced heat transport observed in the Tritium plasma is not captured in the GENE and ASTRA-TGLF-SAT2 simulations by simply changing the isotope mass for the same input profiles.
Isotope removal experiment in JET-ILW in view of T-removal after the 2nd DT campaign at JET
(2022-04) Wauters, T.; Matveev, D.; Douai, D.; Banks, J.; Buckingham, R.; Carvalho, I. S.; De La Cal, E.; Delabie, E.; Dittmar, T.; Gaspar, J.; Huber, A.; Jepu, I.; Karhunen, J.; Knipe, S.; Maslov, M.; Meigs, A.; Monakhov, I.; Neverov, V. S.; Noble, C.; Papadopoulos, G.; Pawelec, E.; Romanelli, S.; Shaw, A.; Sheikh, H.; Silburn, S.; Widdowson, A.; Abreu, P.; Aleiferis, S.; Bernardo, J.; Borodin, D.; Brezinsek, S.; Buermans, J.; Card, P.; Carvalho, P.; Crombe, K.; Dalley, S.; Dittrich, L.; Elsmore, C.; Groth, M.; Hacquin, S.; Henriques, R.; Huber, V.; Jacquet, P.; Jiang, X.; Jones, G.; Keeling, D.; Kinna, D.; Kumpulainen, H.; Siren, P.; Varje, J.; , JET Contributors
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
A sequence of fuel recovery methods was tested in JET, equipped with the ITER-like beryllium main chamber wall and tungsten divertor, to reduce the plasma deuterium concentration to less than 1% in preparation for operation with tritium. This was also a key activity with regard to refining the clean-up strategy to be implemented at the end of the 2nd DT campaign in JET (DTE2) and to assess the tools that are envisaged to mitigate the tritium inventory build-up in ITER. The sequence began with 4 days of main chamber baking at 320 °C, followed by a further 4 days in which Ion Cyclotron Wall Conditioning (ICWC) and Glow Discharge Conditioning (GDC) were applied with hydrogen fuelling, still at 320 °C, followed by more ICWC while the vessel cooled gradually from 320 °C to 225 °C on the 4th day. While baking alone is very efficient at recovering fuel from the main chamber, the ICWC and GDC sessions at 320 °C still removed slightly higher amounts of fuel than found previously in isotopic changeover experiments at 200 °C in JET. Finally, GDC and ICWC are found to have similar removal efficiency per unit of discharge energy. The baking week with ICWC and GDC was followed by plasma discharges to remove deposited fuel from the divertor. Raising the inner divertor strike point up to the uppermost accessible point allowed local heating of the surfaces to at least 800 °C for the duration of this discharge configuration (typically 18 s), according to infra-red thermography measurements. In laboratory thermal desorption measurements, maintaining this temperature level for several minutes depletes thick co-deposit samples of fuel. The fuel removal by 14 diverted plasma discharges is analysed, of which 9, for 160 s in total, with raised inner strike point. The initial D content in these discharges started at the low value of 3%-5%, due to the preceding baking and conditioning sequence, and reduced further to 1%, depending on the applied configuration, thus meeting the experimental target.