Search

The toroidal single-fluid magnetohydrodynamic (MHD) code MARS-F (Liu et al 2000 Phys. Plasmas 7 3681) and the MHD-kinetic hybrid code MARS-K (Liu et al 2008 Phys. Plasmas 15 112503) are utilized to study the plasma response to the n = 1 (n is the toroidal mode number) resonant magnetic perturbation (RMP), applied to suppress the type-I edge localized mode (ELM) in a KSTAR discharge. Both the resistive-rotating and ideal-static plasma models identify strong screening of the resonant radial field harmonics of the applied RMP due to the plasma response, and predict a strong edge-peeling response of the plasma which is consistent with the optimal ELM control coil current configuration adopted in experiment. The RMP-induced radial displacement of the plasma, computed by the resistive-rotating plasma model, agrees reasonably well with that reconstructed from the measured data in the plasma core. Taking into account the drift kinetic response of fast ions, MARS-K hybrid modeling also finds quantitative agreement of the plasma core fluid pressure perturbation with experiment. Based on the MARS-F computed plasma response, a guiding-center orbit-tracing simulation finds about 0.3% of fast ion losses due the n = 1 RMP in the KSTAR ELM control experiment considered. Most losses are associated with counter-current fast ions located near the plasma edge. [ABSTRACT FROM AUTHOR]

BackgroundThe control of edge localized modes (ELMs) is a key issue for the safety operation of ITER and future magnetic confinement fusion reactors. In recent years, extensive theoretical simulations and experimental studies have demonstrated that resonant magnetic perturbation (RMP) is a promising method for controlling edge localized modes (ELMs) in H-mode plasmas.PurposeThis study aims to investigate drift kinetic resonant effects of thermal particles on the plasma response to the applied RMP and compare with that of the fluid model for better understanding of ELMs control in HL-2A.MethodsBased on experimental plasma and RMP coil configurations in HL-2A, the MARS-F/K codes were employed to compute the drift dynamic response of plasma to RMP under high constraint mode and compared it with the results of fluid model. Further sensitivity studies were conducted on key parameters including the plasma equilibrium pressure, toroidal flow as well as the thermal particle collision effects.ResultsThe fluid response model predicts an initially relatively weak enhancement of the plasma response amplitude with the equilibrium pressure parameter βN, followed by a strong variation as βN approaches the Troyon no-wall beta limit. The latter is unphysical and is eliminated by the kinetic response model. Including kinetic response and considering particle collision, the non-adiabatic resonant contribution of trapped thermal ions is found to be significant. Neglecting the particle collision, however, the trapped thermal electron contribution becomes more pronounced.ConclusionsThe importance of considering kinetic effects for high-beta plasma response is emphasized by this study. It is important to include the non-adiabatic resonant contribution of trapped particles to the kinetic response while taking into account the particle collision effect.

Copyright of Journal of Donghua University (Natural Science Edition) is the property of Journal of Donghua University (Natural Science) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The influence on the loss of energetic passing ions by the n = 4 resonant magnetic perturbation (RMP) is investigated through numerical simulations (here, n is the toroidal mode number of the RMP field). Dedicated efforts have been made to uncover how the plasma response modifies the loss fractions and underlying mechanisms. The stochastization of the drift surfaces and the particle loss fractions increase significantly under the response field, in which the resonant component is significantly shielded. In order to better understand how the response field contributes a considerable drift island width, the respective effect of each poloidal component $m_\mathrm{b}$ on the outermost drift island $m_\mathrm{p}/n = 9/4$ are compared (here, $m_\mathrm{b}$ and $m_\mathrm{p}$ are poloidal mode numbers of the RMP components and drift island, respectively). Contrary to the intuition that the components with $m_\mathrm{b} = m_\mathrm{p} \pm 1$ should dominate the sideband resonance, some of the components which fulfill $|m_\mathrm{p}-m_\mathrm{b}|\gg 1$ have the dominant contributions under the response field. There are mainly two reasons accounting for this phenomenon, i.e. the drift motion of particles and the enhancement of amplitudes of non-resonant high- m components by the plasma response near the edge due to the resonant field amplification (RFA) effect. The former made it possible for particles to resonate with the far non-resonant components, and the latter significantly enhanced the perturbation field experienced by particles. The above results imply that the RFA effect is more critical than the stochastization of magnetic topology in the fast ion losses under RMP.

The toroidal single-fluid magnetohydrodynamic (MHD) code MARS-F (Liu et al 2000 Phys. Plasmas 7 3681) and the MHD-kinetic hybrid code MARS-K (Liu et al 2008 Phys. Plasmas 15 112503) are utilized to study the plasma response to the n = 1 ( n is the toroidal mode number) resonant magnetic perturbation (RMP), applied to suppress the type-I edge localized mode (ELM) in a KSTAR discharge. Both the resistive-rotating and ideal-static plasma models identify strong screening of the resonant radial field harmonics of the applied RMP due to the plasma response, and predict a strong edge-peeling response of the plasma which is consistent with the optimal ELM control coil current configuration adopted in experiment. The RMP-induced radial displacement of the plasma, computed by the resistive-rotating plasma model, agrees reasonably well with that reconstructed from the measured data in the plasma core. Taking into account the drift kinetic response of fast ions, MARS-K hybrid modeling also finds quantitative agreement of the plasma core fluid pressure perturbation with experiment. Based on the MARS-F computed plasma response, a guiding-center orbit-tracing simulation finds about 0.3% of fast ion losses due the n = 1 RMP in the KSTAR ELM control experiment considered. Most losses are associated with counter-current fast ions located near the plasma edge.

A new type of resonant magnetic perturbation (RMP), generated by helical coils, is proposed for controlling the edge localized mode (ELM) in H-mode tokamak plasmas. The helical coil optimization utilizes the MARS-F code (Liu et al 2000 Phys. Plasmas 7 3681) computed linear resistive fluid response of the plasma to the applied RMP field. The optimal helical coils are found to be located near the outboard mid-plane of the torus, with relatively simple shape but tilted towards the equilibrium magnetic field line pitch. Compared to the window-frame ELM control coils, the optimal helical coils require 2–4 times less current, in order to achieve the same ELM control performance specified by various figures of merit adopted in this work. The results from the present study show a promising path forward in achieving ELM control with RMP fields in tokamak plasmas.

The striation pattern of heat loads on the divertor targets is determined by the plasma response to external resonant magnetic perturbations (RMPs) applied for suppression of edge localized modes (ELMs). Ideal and kinetic plasma response analysis with the general perturbed equilibrium code (GPEC) has shown that the extent of this striation pattern is very sensitive to the radial location of equilibrium truncation in GPEC, and that a significantly smaller extent is found if the equilibrium is truncated closer to the separatrix. Depending on the choice of truncation, it is shown in EMC3-EIRENE simulations that the peak heat load can be reduced by adjusting RMP coil parameters (phase, amplitude) within a window that is consistent with ELM suppression.

Both linear and quasi-linear aspects of the plasma response to the resonant magnetic perturbation (RMP) field are numerically investigated for various H-mode scenarios in ITER, covering the pre-fusion power operation and the fusion power operation phases. Linear response computations for eight ITER scenarios, with varying plasma current and toroidal magnetic field, reveal that the best coil current phasing for controlling the type-I edge localized modes (ELMs) scales roughly linearly with the edge safety factor. The coil phasing is defined as the relative toroidal phase of the coil currents between different rows, for a given toroidal harmonic. Quasi-linear initial value simulation, which is the focus of the present study, shows that application of the n = 3 (n is the toroidal mode number) RMP field has a minimum side effect on the plasma core momentum confinement but potentially a large effect on the global particle transport. Generally, the RMP field with the best (worst) coil phasing for ELM control produces the strongest (weakest) effect on the plasma edge flow and the overall density. This robustly holds for all eight ITER scenarios. Consequently, in order to minimize the RMP induced side effects while achieving ELM control (suppression) in ITER, a compromise is necessary in choosing the coil current configuration. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of a dietary mixture based on extruded linseed and pea (ELP; 20:80 w/w) and probiotics (L. acidophilus) on the performance, biochemical responses, breast muscle fatty acids (FA) profile, and lipid indices in broiler chickens. A total of 480 one-day-old Ross 308 broilers were assigned into four groups in a 2 × 2 factorial arrangement with two levels of ELP (0% and 30%) at the expense of soybean meal, corn, and vegetable oil and two levels of probiotic (0 and 20 g ton−1 feed). There were no effects of ELP diet or probiotic supplementation on performance and carcass traits. Feeding the ELP diet increased plasma total protein, urea nitrogen (PUN), and creatinine (Cre) levels with no changes in the PUN/Cre ratio. A probiotic addition lowered the total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and the TC/HDL-C and LDL-C/HDL-C ratios. The ELP diet improved the breast muscle FA profile by lowering total saturated FA (SFA) and increasing total polyunsaturated FA (PUFA), omega-3 (n-3), unsaturated FA (UFA), PUFA/SFA, and UFA/SFA ratios. Probiotics increased total PUFA, omega-6 (n-6) and decreased the n-6/n-3 ratio, total UFA, and UFA/SFA ratio. Dietary treatment interaction exhibited a synergistic effect for total PUFA and an antagonistic effect for n-3 PUFA and n-6/n-3 PUFA ratio in breast muscle. Probiotics reduced some lipid indices (PUFA/SFA ratio, desirable FA and nutritive value index) only when ELP0 was fed. In conclusion, based on these results, using ELP30 alone in broiler diets is recommended to improve meat's nutritional value for consumers. [ABSTRACT FROM AUTHOR]

The effects of resonant magnetic perturbation (RMP) fields on peeling–ballooning (P–B) modes are studied with the experimental equilibria of EAST based on the four-field model in BOUT++ code. As the two basic types of plasma responses, the magnetic and the transport response to RMP are considered in our simulation to reveal the roles of the plasma response during edge localized mode mitigation. On the one hand, the results show that RMP can reduce the linear growth rates of the P–B modes and the pedestal energy loss in the nonlinear process by directly coupling with the P–B modes. The magnetic response can weaken the impacts of RMPs on the P–B modes by partially screening the applied RMP fields more precisely the resonant components. On the other hand, RMP can further reduce the linear growth rates of the P–B modes and the pedestal energy loss by changing the equilibrium pressure profiles through the transport response. More detailed analysis suggests that, compared with other resonant components of RMPs, the components whose corresponding rational surfaces are located at the top of the pedestal can lead to stronger reductions in the linear growth rates of the P–B modes, and can reduce pedestal energy loss more significantly by enhancing multi-mode coupling in the nonlinear process. Finally, the multi-mode coupling increases with the strength of the resonant components, so one can change the RMP poloidal spectrum by adjusting the phase difference ${{\Delta }}\phi $ between the upper and low RMP coils from $0$ to ${360^\circ }$ , and hence obtain the optimal coil phase difference that leads to the strongest reductions in the linear growth rates of the P–B modes and the pedestal energy loss through maximizing the strength of resonant components, especially the resonant components whose corresponding rational surfaces are located at the top of the pedestal.

Linear plasma response modeling is exploited in this work to assess the effect of different coil configurations on edge localized mode (ELM) stability in full power operational scenarios for the Divertor Tokamak Test (DTT) facility, presently under construction at the ENEA site of Frascati (Italy). The MARS-F code is used to compute, in toroidal geometry and including flow, the resistive plasma response to different vacuum fields with toroidal mode numbers $n\,=\,1,2,3$ . Peeling-like response in particular, correlated with ELM control, is found to be significant for $n\,=\,2,3$ perturbations while $n\,=\,1$ induces a large core response in the investigated scenarios. Two metrics are used to link plasma response to ELM control. Namely the local normal plasma displacement in the x -point region and the Chirikov parameter in PEST-like straight-field-line coordinates. These criteria are used to predict optimal phasing of the active coil arrays and current thresholds based on empirical evidence. Depending on the number of active coils and on the scenario, coil currents between 20 and 40 kAt are predicted to be effective for ELM mitigation in DTT.

We report the observation of improved confinement discharge in a magnetic braking experiment in the KSTAR tokamak. The improved confinement is achieved with reduced toroidal plasma rotation by non-axisymmetric magnetic field induced toroidal rotation braking along with significant reduction of edge localized modes (ELMs). Modifications in multi-channel transport raise fast ion slowing-down time and improve neutral beam deposition, leading to improved fast ion confinement. We show that modifications of radial electric field and E × B shear flow by magnetic braking provoke an enhanced pedestal to sustain thermal confinement against degradation in the typical 3D field experiment.

This study evaluated the effects of a dietary mixture based on extruded linseed and pea (ELP; 20:80 w/w) and probiotics (L. acidophilus) on the performance, biochemical responses, breast muscle fatty acids (FA) profile, and lipid indices in broiler chickens. A total of 480 one-day-old Ross 308 broilers were assigned into four groups in a 2 × 2 factorial arrangement with two levels of ELP (0% and 30%) at the expense of soybean meal, corn, and vegetable oil and two levels of probiotic (0 and 20 g ton−1 feed). There were no effects of ELP diet or probiotic supplementation on performance and carcass traits. Feeding the ELP diet increased plasma total protein, urea nitrogen (PUN), and creatinine (Cre) levels with no changes in the PUN/Cre ratio. A probiotic addition lowered the total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and the TC/HDL-C and LDL-C/HDL-C ratios. The ELP diet improved the breast muscle FA profile by lowering total saturated FA (SFA) and increasing total polyunsaturated FA (PUFA), omega-3 (n-3), unsaturated FA (UFA), PUFA/SFA, and UFA/SFA ratios. Probiotics increased total PUFA, omega-6 (n-6) and decreased the n-6/n-3 ratio, total UFA, and UFA/SFA ratio. Dietary treatment interaction exhibited a synergistic effect for total PUFA and an antagonistic effect for n-3 PUFA and n-6/n-3 PUFA ratio in breast muscle. Probiotics reduced some lipid indices (PUFA/SFA ratio, desirable FA and nutritive value index) only when ELP0 was fed. In conclusion, based on these results, using ELP30 alone in broiler diets is recommended to improve meat’s nutritional value for consumers.

The divertor biasing technique offers a promising alternative to control the edge localized mode (ELM) as well as the divertor heat load in tokamaks, as compared to the resonant magnetic perturbation (RMP) generated by magnetic coils. The linear resistive MHD code MARS-F (Liu et al 2000 Phys. Plasmas 7 3681) is employed to study the plasma response to the n = 2 ( n is the toroidal mode number) field perturbation in HL-2A, produced by the divertor biasing current filaments flowing in the scrape-off layer region. The response field due to biasing currents is compared with the RMP field utilized for ELM control in HL-2A. The strength of the radial resonant field perturbation, produced by the biasing currents of 100 A level, is found to be comparable with RMP generated by several kA of ELM control coil currents for the reference plasma. The plasma normal displacement near the X-point and the associated neoclassical toroidal viscosity torque are also computed to be similar between these two techniques. The modeling results thus strongly suggest that the biasing technique can be applied to control ELMs. Moreover, the biasing currents produce field perturbations, including the plasma response, that are localized more near the plasma edge (compared to the RMP counterpart), thus reducing the chance of mode locking associated with core perturbations. Particle orbit tracing also reveals that the biasing current produced magnetic perturbation tends to widen the heat deposition region and induce the strike point splitting of the ion saturation flow on the outer divertor surface, consistent with experimental observations in HL-2A. These toroidal modeling results confirm the possibility of ELM control and plasma exhaust solution by the divertor biasing technique.

In certain circumstances, plasma response suppresses magnetic islands expected at perturbed resonant magnetic surfaces. We investigate the plasma response to the resonant magnetic perturbations in a large aspect ratio tokamak perturbed by external resonant helical windings, considering polar toroidal coordinates for which analytical toroidal equilibrium solutions and perturbing fields are available. We apply an empirical approach to mimic the plasma screening effects by introducing presumed plasma current sheets on the resonance surfaces to cancel the RMP effects. Numerical examples show the effect of plasma response reducing magnetic islands at the plasma edge and also regularizing field lines around the resonant surface. The distribution of connection lengths along the plasma cross section indicates that the plasma response increases the connection lengths since more toroidal turns are performed until a field line reaches the tokamak wall. [ABSTRACT FROM AUTHOR]

In this paper, a plasma response model is investigated for large aspect ratio tokamaks, on the presence of external nonaxisymmetric resonant magnetic perturbations. To control plasma confinement, the plasma is perturbed by external resonant helical windings, similar to those introduced by an ergodic magnetic limiter. The plasma response to the perturbation is modeled as an additional magnetic perturbation, created by a current sheet on the main perturbed resonant surface, vanishing the radial component of the total magnetic field in the considered resonant surface. In order to show the influence of the plasma response on the field line topology, the field line differential equations are integrated numerically, showing the reduction of magnetic island sizes and the regularization of chaotic regions around the resonant surface where the response was introduced, in agreement with results observed in sophisticated simulation codes. Finally, the connection lengths indicate that, regarding their distribution, the plasma response introduces a homogenization effect which may affect the deposition patterns at the tokamak wall. [ABSTRACT FROM PUBLISHER]

Several studies suggest that β -cryptoxanthin has a greater plasma response from its common food sources than other carotenoids such as β -carotene and lycopene. The hypothesis of this study is that changes in plasma β -cryptoxanthin concentrations will be greater than changes in plasma β -carotene or lycopene concentrations even if these carotenoids are fed in a similar food matrix, such as citrus fruit. We tested this hypothesis by measuring changes in plasma concentrations of β -cryptoxanthin, lycopene, and β -carotene after feeding measured amounts of canned tangerines and pink grapefruit to healthy nonsmoking adult humans. Volunteers served as their own controls and received both citrus fruit treatments randomly. In the first study, 8 subjects ate single meals of 234-304 g of tangerines or 60-540 g of pink grapefruit. The second study compared changes in plasma carotenoid concentration caused by feeding 234 g of tangerines or 540 g of pink grapefruit to 11 subjects. Blood was collected 5 times within 24 hours after each citrus meal. Carotenoid concentrations were analyzed by reversed-phase high-performance liquid chromatography. Plasma β -cryptoxanthin concentrations increased within 5 hours and then stabilized, remaining high throughout the 24 hours measured. Plasma concentrations of lycopene and β -carotene did not change. These results show that β -cryptoxanthin concentrations increased after a citrus fruit meal, but lycopene and β -carotene concentrations did not change after a similar citrus fruit meal. These results support our hypothesis that changes in plasma β -cryptoxanthin are greater than changes in plasma lycopene or β -carotene, even when these carotenoids are fed in a similar food matrix. [ABSTRACT FROM AUTHOR]

Abstract: A multibatch formulation of a multi-input multi-output closed-loop subspace system identification method is employed for the purpose of obtaining control-relevant models of the vacuum-plasma response in the magnetic confinement fusion experiment EXTRAP T2R. The accuracy of the estimate of the plant dynamics is estimated by computing bootstrap replication statistics of the dataset. It is seen that the thus identified models exhibit both predictive capabilities and physical spectral properties. [Copyright &y& Elsevier]

Bioavailability of nutrients is highly diverse and depends on a variety of endogenous and exogenous factors in humans. This data article reports on the plasma response of 10 human subjects (5 females, 5 males) to a single dose of a multivitamin drink within 6h (blood taken after 1, 2, 4, and 6h). Nutrients, which were considered in the assessment, were folate (Radioimmuno Assay), vitamin B12 (Radioimmuno Assay) and resveratrol and its plasma metabolites resveratrol-3- O -glucuronide (R3G), resveratrol-4'- O -glucuronide (R4G), resveratrol-3- O -sulfate (R3S) and resveratrol-3- O -4'- O -disulfate (RD, all HPLC). Biological outcome measures were malondialdehyde (MDA, HPLC) and Ferric Reducing ability potential (FRAP, Microplate reader). Mean plasma concentration increased over time significantly for folate (p < 0.05, maximum concentration (Tmax) after 2h), R3G, R4G, R3S (all p < 0.05, Tmax after 1h), RD (p < 0.05, Tmax after 2h) as well as MDA, which decreased (p < 0.05, Tmax after 2h). No significant change was observed for vitamin B12 and FRAP. Within this mean development, individual changes of participants were highly diverse such as for folate from +42 to +422%, for MDA from -49 to +30% or vitamin B12 from -4 to +33%. For R4G 4 out of 10 subjects showed even no increase in plasma at all. For R4G plasma response ranged from 0 to 36 ng/ml, for R3G from 0 to 53 ng/ml or for R4S from 62 to 265 ng/ml. There was no gender difference regarding the plasma response., (© 2020 The Authors.)