Heating Scenarios Research Articles

Generation and observation of fast deuterium ions and fusion-born alpha particles in JET plasmas with the 3-ion radio-frequency heating scenario

Dedicated experiments to generate energetic D ions and fusion-born alpha particles were performed at the Joint European Torus (JET) with the ITER-like wall (ILW). Using the 3-ion radio frequency (RF) heating scenario, deuterium ions from neutral beam injection (NBI) were accelerated in the core of mixed plasmas to higher energies with ion cyclotron resonance frequency (ICRF) waves, in turn leading to a core-localized source of alpha particles. The fast-ion distribution of RF-accelerated D-NBI ions was controlled by varying the ICRF and NBI power ( 4–6 MW, 3–20 MW), resulting in rather high D-D neutron (≈ 1 × 1016 s−1) and alpha rates (≈ 2 × 1016 s−1) at moderate input heating power. Theory and TRANSP analysis shows that large populations of co-passing MeV-range D ions were generated using the 3-ion ICRF scenario. This important result is corroborated by several experimental observations, in particular gamma-ray measurements. The developed experimental scenario at JET provides unique conditions for probing several aspects of future burning plasmas, such as the contribution from MeV range ions to global confinement, but without introducing tritium. Dominant fast-ion core electron heating with and a rich variety of fast-ion driven Alfvén eigenmodes (AEs) were observed in these plasmas. The observed AE activities do not have a detrimental effect on the thermal confinement and, in some cases, may be driven by the fusion born alpha particles. A strong continuous increase in neutron rate was observed during long-period sawteeth (1 s), accompanied by the observation of reversed shear AEs, which implies that a non monotonic q profile was systematically developed in these plasmas, sustained by the large fast-ion populations generated by the 3-ion ICRF scenario.

High frequency Alfvén eigenmodes detected with ion-cyclotron-emission diagnostics during NBI and ICRF heated plasmas on the ASDEX Upgrade tokamak

The paper presents the first reported observation of high frequency Alfvén eigenmode excitation on the ASDEX Upgrade tokamak. The mode is driven in a novel way using radio frequency (RF) wave acceleration of either beam-injected deuterium ions or thermal He-3 minority ions in a three-ion heating scenario. In the case of beam ion acceleration, the instability only appears during deuteron acceleration at the third beam ion cyclotron harmonic (wave frequency ω = 3ΩD where ΩD is the deuterium cyclotron frequency), as the mode is not detected during the more commonly used second harmonic/minority heating scenario or in the absence of beam-injected ions. The mode frequency is around 0.6–0.7ΩD, where ΩD is evaluated in the low-field side plasma edge, and tracks the magnetic field B and the edge plasma electron density ne via the Alfvénic relation ω ∼ B ne −1/2. The mode does not appear as a single frequency wave but as a bundle of closely spaced (in frequency) sub-modes. When the parallel beam ion velocity component is increased, the sub-mode frequency spacing is observed to decrease, possibly due to a change in the eigenmode structure. Under certain conditions, typically in discharges with a relatively low plasma current, IP < 0.7 MA, the mode appears to be driven directly by sub-Alfvénic deuterium beam ions. Absolute measurements of the mode amplitude show that at least 1% of the beam-injected power is transferred non-collisionally to the instability. While this is too low for practical alpha-channeling applications, discharges are planned with the aim of increasing the level of power transferred non-collisionally between fast ions and the instability.

Parent, alkylated, oxygenated and nitrated polycyclic aromatic hydrocarbons in PM2.5 emitted from residential biomass burning and coal combustion: A novel database of 14 heating scenarios.

To characterize the emissions of polycyclic aromatic hydrocarbons (PAHs) from residential biomass burning and coal combustion in field environments, smoke samples were collected from the combustion of six types of biomass in heated kangs and four types of coal in traditional stoves and semi-gasifier stoves. The emission factors (EFs) of the total PAH were in the range of 84.5-344mg/kg for biomass burning, with lower EFs for biomass with higher densities, and in the range of 38.0-206mg/kg for coal combustion, with lower EFs for coals with higher maturity. Moreover, EFs were lower from high-density biomass fuels (wood trunk, 84.5±11.3mg/kg) than low-maturity coals (bituminous coal, 206±16.5mg/kg). Parent, oxygenated, alkylated, and nitrated PAHs accounted for 81.1%, 12.6%, 6.2%, and 0.1%, respectively, of the total-PAH EFs from biomass burning, and 84.7%, 13.8%, 1.4%, and 0.1%, respectively, of the total-PAH EFs from coal combustion. PAH source profiles differed negligibly between biomass fuels but differed significantly between bituminous coal and anthracite coal fuels. The characteristic species of sources were phenanthrene, 9-fluorenone, and 2-nitrobiphenyl for biomass burning, and were phenanthrene, benzo[ghi]perylene, 1,4-naphthoquinone, and 2-nitrobiphenyl for coal combustion. The ratios of benzo[b]fluoranthene/(benzo[b]fluoranthene+benzo[k]fluoranthene) were 0.40-0.45 for biomass burning and 0.89-0.91 for coal combustion, and these significantly different values constitute unique markers for distinguishing these fuels in source apportionment. Benzo[a]pyrene-equivalent factor emissions were 2.79-11.3mg/kg for biomass and 7.49-41.9mg/kg for coal, where parent PAHs contributed 92.0%-95.1% from biomass burning and 98.6%-98.8% from coal combustion. Total-PAH emissions from residential heating were 1552t across Shaanxi province, to which wheat straw (445t) in biomass burning and bituminous coal (438t) in coal combustion were the highest contributors. Results from this study provide crucial knowledge for the source identification of PAHs as well as for the design of abatement strategies against pollutant emissions.

ELM Suppression by Boron Powder Injection and Comparison with Lithium Powder Injection on EAST

Type I edge-localized modes (ELMs) in the Experimental Advanced Superconducting Tokamak (EAST) were completely suppressed via boron powder injection into the X-point region of an upper-single null configuration over a wide range of operating conditions (2.8 < Paux < 7.5 MW, 3.8 × 1019 < ne < 6 × 1019 m−3, RF-only and RF + NBI heating scenarios, both grad-B drift directions, and even He ion majority plasmas) (Sun et al. in Nucl. Fusion, 2020). A window of edge B concentration for stable long pulse operation was identified: too low and ELMs return, too high and the discharge suffers radiative collapse. The injection of boron powder above the minimum for ELM suppression coincided with the occurrence of an edge harmonic oscillation detected in magnetics (both on the high-field side and low-field side), in AXUV diodes near the upper X-point, divertor D $${\upalpha }$$ emission, and in a range of other diagnostics (Diallo et al. in: Proceedings of 2020 IAEA fusion energy conference, 2021). No harmonic oscillation was observed when ELMs were present, and stored energy was slightly increased at constant density during ELM suppression. Core tungsten emission during ELM suppression either increased or decreased relative to ELMy H-mode, but the W emission was maintained at acceptable levels. The threshold B injection rate was measured for several conditions, and found to increase with heating power. Li powder injection into comparable discharges also resulted in a short phase of ELM suppression, but density and stored energy both decreased due to the strong pumping effect of lithium; no edge harmonic oscillation was observed with Li injection, indicating that the ELM suppression mechanisms differ. The new set of B-seeded, ELM-suppressed discharges exhibited certain characteristics of quiescent H-mode (Burrell et al. in Phys Plasmas 8:2153, 2001), but did not require high shear, counter beams, etc. The wide operating window and compatibility with RF-only discharges paves the way for future experiments targeting long pulse H-mode discharges with complete ELM suppression.

Physics basis for the ICRF system of the SPARC tokamak

Ion cyclotron range of frequencies (ICRF) heating will be the sole auxiliary heating method on SPARC for both full-field (Bt0 ~ 12 T) D–T operation and reduced field (Bt0 ~ 8 T) D–D operation. Using the fast wave at ~120 MHz, good wave penetration and strong single-pass absorption is expected for D–T(3He), D(3He), D(H) and4He(H) heating scenarios. The dependences of wave absorption on${k_\parallel }$,3He concentration, resonance location, antenna poloidal location and losses on alpha particles and ash have been studied. The antenna loading has been assessed by comparison with the Alcator C-Mod antennae. An antenna spectrum of${k_\parallel }\sim 15\text{--}18\,{\textrm{m}^{ - 1}}$is shown to be good for both core absorption and edge coupling. For the control of impurity sources, the antenna straps are rotated ~10° to be perpendicular to the B field and the straps can run with different power levels in order to optimize the antenna spectrum and to minimize the image current on the antenna frame. Combining the physics constraints with the SPARC port design, maintenance requirement and contingency against antenna failure during D–T operation, we plan to mount on the inner wall of the vacuum vessel a total of 12 4-strap antennae in 6 ports while keeping 3-strap antennae that are insertable and removable on port plugs as the backup option.

GRB spectrum from gradual dissipation in a magnetized outflow

ABSTRACT Modelling of many gamma-ray burst prompt emission spectra sometimes requires a (quasi) thermal spectral component in addition to the Band function that sometimes leads to a double-hump spectrum, the origin of which remains unclear. In photospheric emission models, a prominent thermal component broadened by sub-photospheric dissipation is expected to be released at the photospheric radius, $r_{\rm ph}\sim 10^{12}\,$ cm. We consider an ultra-relativistic strongly magnetized steady outflow with a striped-wind magnetic-field structure undergoing gradual and continuous magnetic energy dissipation at r &amp;lt; rs that heats and accelerates the flow to a bulk Lorentz factor Γ(r) = Γ∞min [1, (r/rs)1/3], where typically rph &amp;lt; rs. Similar dynamics and energy dissipation rates are also expected in highly variable magnetized outflows without stripes/field-reversals. Two modes of particle energy injection are considered: (a) power-law electrons, e.g. accelerated by magnetic reconnection, and (b) distributed heating of all electrons (and e±-pairs), e.g. due to magnetohydrodynamic instabilities. Steady-state spectra are obtained using a numerical code that evolves coupled kinetic equations for a photon-electron-positron plasma. We find that (i) the thermal component consistently peaks at $(1+z)E_{\rm pk}\sim 0.2-1\,$MeV, for a source at redshift z, and becomes sub-dominant if the total injected energy density exceeds the thermal one, (ii) power-law electrons cool mainly by synchrotron emission whereas mildly relativistic and almost monoenergetic electrons in the distributed heating scenario cool by Comptonization on thermal peak photons, (iii) both scenarios can yield a low-energy break, and (iv) the $\sim 0.5(1+z)^{-1}\,$ keV X-ray emission is suppressed in scenario (a), whereas it is expected in scenario (b). Energy-dependent linear polarization can differentiate between the two particle heating scenarios.

Analysis of the factors influencing the airflow behavior in an impinging jet ventilation room

A validated CFD model is employed to predict the airflow behavior in an impinging jet ventilation (IJV) room with cool, isothermal or warm jets. By using the numerical results, the influences of jet discharge height, supply grille shape and room height on the jet flow behavior as well as the draught discomfort are analyzed for IJV operating in heating scenarios. The results indicate that the warm supply jet of IJV rises upward to the ceiling after spreading along the floor for a certain distance due to thermal buoyancy, resulting in a limited dispersion area, while the cool and isothermal jets of IJV always spread along the whole floor. When IJV is used for space heating, the lower the jet discharge height, the farther the supply air spreads along the floor, and the supply grille shape and room height almost have no effect on the air dispersion area. The results also show that the energy-efficient advantage of IJV in its heating mode compared to the mixing ventilation (MV) system is more remarkable in higher rooms. Moreover, there is a risk of draught discomfort in IJV heating rooms and it is recommended to wear socks to avoid this discomfort.

Observation of helical m/n = 1/1 saturated steady mode in EAST pure electron heating scenario with q0 ≼ 1

We observed for the first time a helical m/n = 1/1 (m is the poloidal mode number and n is the toroidal mode number) saturated steady mode (SSM) in the center of the EAST electron heating dominant plasma where the core safety factor was close to but slightly below unity and the profile had an extreme peak at the plasma center ( is the electron temperature). An internal crash can be caused by the dynamics of the SSM, and its influence on the electron temperature profile is as large as that of a typical sawtooth crash (SC) in magnitude. Due to the weak magnetic shear in the core, the SSM regularly exhibits an m/n = 2/2 harmonic component. For low shear auxiliary heated plasma, the SSM cannot cause the degradation of plasma confinement ( or ), but an SC is indeed a harmful factor. Three-dimensional resistive magnetohydrodynamic simulations with a realistic EAST strong elongated magnetic configuration, a high Lundquist number () and a strong central peaked pressure profile, have been made to demonstrate the formation of the SSM in the case of and the destabilization of the SC in another case with . These nonlinear simulation results agree well with the observations of both the SSM and SC in EAST electron heating dominant discharges with an extreme central peaked . An M3D simulation found that the SC is caused by additional newly developed harmonics of the m/n = 1/1 helical instability. Nonlinear simulation also predicted a modulation of the SSM on current in the plasma core, which is favorable for maintaining in the plasma core. Furthermore, nonlinear simulation also showed that a small toroidal plasma flow can be generated by the SC.

Effect of Device Configuration and Patient's Body Composition on the RF Heating and Nonsusceptibility Artifact of Deep Brain Stimulation Implants During MRI at 1.5T and 3T.

Patients with deep brain stimulation (DBS) implants have limited access to MRI due to safety concerns associated with RF-induced heating. Currently, MRI in these patients is allowed in 1.5T horizontal bore scanners utilizing pulse sequences with reduced power. However, the use of 3T MRI in such patients is increasingly reported based on limited safety assessments. Here we present the results of comprehensive RF heating measurements for two commercially available DBS systems during MRI at 1.5T and 3T. To assess the effect of imaging landmark, DBS lead configuration, and patient's body composition on RF heating of DBS leads during MRI at 1.5T and 3T. Phantom and ex vivo study. Gel phantoms and cadaver brain. 1.5T and 3T, T1 -weighted turbo spin echo. RF heating was measured at the tips of DBS leads implanted in brain-mimicking gel. Image artifact was assessed in a cadaver brain implanted with an isolated DBS lead. Descriptive. We observed substantial fluctuation in RF heating, mainly affected by phantom composition and DBS lead configuration, ranging from 0.14°C to 23.73°C at 1.5T, and from 0.10°C to 7.39°C at 3T. The presence of subcutaneous fat substantially altered RF heating at the electrode tips (3.06°C < ∆T < 19.05° C). Introducing concentric loops in the extracranial portion of the lead at the surgical burr hole reduced RF heating by up to 89% at 1.5T and up to 98% at 3T compared to worst-case heating scenarios. Device configuration and patient's body composition substantially altered the RF heating of DBS leads during MRI. Interestingly, certain lead trajectories consistently reduced RF heating and image artifact. Level of Evidence 1 Technical Efficacy Stage 1 J. MAGN. RESON. IMAGING 2021;53:599-610.

Excitation of elliptical and toroidal Alfvén eigenmodes by 3He-ions of the MeV-energy range in hydrogen-rich JET plasmas

Elliptical (EAE) and toroidal Alfvén eigenmode (TAE) instabilities have been observed in hydrogen-rich JET discharges of the D-(3He)-H ion cyclotron resonance heating (ICRH) scenario, which is characterized by strong absorption of radio frequency waves at very low concentrations of the resonant 3He-ions. In the experiments, core localized TAEs with a frequency fTAE ≈ 280 kHz with mode numbers n= 3, 4, 5 and 6 were detected. Following the phase with TAE excitation, EAE modes at higher frequencies fEAE ≈ 550–580 kHz with mode numbers n = 1, 3, 5 were seen. These high frequency modes indicate that a MeV range population of trapped energetic ions was present in the plasma. The experimental evidence of existence of the MeV-energy 3He-ions able to excite the AEs is provided by neutron and gamma-ray diagnostics as well as fast ion loss measurements. The ICRH modelling code calculations confirm the acceleration of 3He-ions to MeV energies. The magnetohydrodynamic (MHD) analysis results are consistent with the experimental data showing that the MeV 3He ions satisfy to resonant conditions interacting with TAE and EAE modes. This experiment demonstrates the efficient plasma heating mimicking the conditions representative for the ITER plasmas and contribute to the understanding of fast-ion interaction with MHD wave modes.

Energy performance and economic feasibility of hot spring-based district heating system – A case study

As a versatile platform for integrating renewable energies, District Heating systems (DHSs) offer a pragmatic approach toward an environmentally benign and sustainable future. This paper puts forward the feasibility evaluation of using geothermal hot spring source Heat pumps (HPs) for district heating of a village situated in the north-west of Iran, with a cold mountain climate. Solar collectors are also integrated into the DHS as a supplementary heat source. To this aim, three different renewable-energy-based district heating scenarios, viz. a Ground-Source-HP-based (GSHP), a combined GSHP-flat-plate-solar-collector (GSHP-SFPC), and a combined GSHP-linear-parabolic-solar-collector (GSHP-SLPC), along with a fossil-fuel-based (FFB) district heating scenario are evaluated. In order to make an impartial comparison, all scenarios are first dynamically optimized based on their Life Cycle Cost (LCC). Then the annual energetic, exergetic, economic, and environmental performance of the studied scenarios is evaluated and discussed. The obtained results demonstrated that the GSHP-SLPC system has the lowest LCC; however, it has the highest initial investment cost. Moreover, while the initial investment cost of the GSHP-SFPC is 19% lower than the GSHP-SLPC, its LCC is only 4.4% higher. Also, the total contribution of renewable energy sources is 54.1%, 60.2%, and 67.9% for the GSHP, GSHP-SFPC, and GSHP-SLPC systems, respectively.

Energy management strategy of active distribution network with integrated distributed wind power and smart buildings

Aiming to achieve the flexible operation of distribution network (ADN), an energy management strategy of ADN with integrated distributed wind power and smart buildings is proposed in this study. First, based on the thermal storage characteristics of buildings, the resistor–capacitor model is used to develop an energy consumption prediction model of smart buildings. Second, the smart buildings are modelled as flexible resources of ADN. A multi-objective ADN model is further formulated based on analytic hierarchy process (AHP) by comprehensively considering constraints of power grid and smart buildings. Then, the unified model of ADN is transformed by second-order conic relaxation to guarantee the global optimal solution. Finally, the scheduling results for the unified model of ADN under different control methods for heating ventilation and air-conditioning (HVAC) systems are compared in the winter heating scenario. In addition, the impact of the demand response capability for smart buildings on the economic and secure operation of the ADN is further analysed. Numerical studies demonstrate that the proposed method can increase the penetration of local wind power, reduce peak-valley load difference and network loss of the grid while ensuring the comfort temperature of customers, and further achieve the flexible operation of ADN.

How does anthropogenic heating affect the thermal environment in a medium-sized Central European city? A case study in Szeged, Hungary

Since the estimation of anthropogenic heating is always problematic in medium-sized cities because of data lacking, we intended to test how much the omission of such data influences the physical consistency in a numerical model (Weather Research and Forecasting – WRF). It was hypothesized that anthropogenic heating is an important input for the model, even in a relatively small urban area, therefore we adapted three different approaches to quantify its spatiotemporal distribution over Szeged, Hungary. Four numerical experiments were performed in the WRF coupled with the single layer canopy scheme, which included the calculated fluxes and an anthropogenic flux-free reference case. By comparing the experiments, we had the opportunity to determine the effects of different anthropogenic heating scenarios on certain meteorological variables near the surface and in the overlying urban boundary layer. The maximum anthropogenic heat release was estimated to be ranging between 0.6 and 31.2 W/m2 in Szeged, with higher values on winter days. This heat surplus contributed to a maximum increase of 1.5 °C in the simulated near-surface air temperature. Depending on the rate of anthropogenic heat release, the urban boundary layer became deeper, and the mixing of heat and momentum was more efficient. Our results have demonstrated that without the consideration of anthropogenic heating, numerical simulations performed to cities similar to Szeged cannot be physically complete.

Numerical investigation of a minority heating scenario in three-ion components plasma on EAST

Heating with the wave in the ion cyclotron range of frequencies (ICRF) has been used in the development of high-performance H-mode operations in EAST. A different ion cyclotron resonance heating scenario in three-ion component plasma with real experimental parameters on EAST was investigated using a numerical tool. Excellent radio frequency wave absorption was found with an extremely low 3He concentration (0.1%–0.4%) in D-H-(3He) plasma, by adjusting the plasma composition appropriately in our simulation. In this case, the 3He fundamental resonance layer is located between the two ion–ion hybrid resonance-cutoff pairs in close proximity, and therefore E+ of the wave was considerably enhanced near the 3He fundamental resonance layer. The minority 3He tail was estimated to be superenergetic (∼1 MeV) because of the high power carried by each resonant 3He ion. The potential of the three-ion ICRF heating means on EAST was shown, and the scenarios investigated are particularly promising for fast particle generation schemes.

Z eff Measurement in Ohmic, L- and H-Mode Plasmas on HL-2A Tokamak

$Z_{\mathrm {eff}}$ is measured by two visible bremsstrahlung diagnostics on HL-2A tokamak, one of which uses a high spectral resolution spectrometer coupled with an electron multiplied CCD (temporal resolution of 100 Hz), and the other uses a filterscope system (temporal resolution of 1 MHz). The bremsstrahlung brightness measured by them coincides with each other very well. $\bar {Z}_{\mathbf {eff}}$ is systematically measured under different discharge conditions, such as divertor and limiter configurations, ohmic and auxiliary heating phases, before and after siliconization, and $L$ – $H$ transition. Under ohmic phase, $\bar {Z}_{\mathbf {eff}}$ is higher in the limiter configuration than that in the divertor configuration by a factor of ~1.5 under high-density regime. $\bar {Z}_{\mathbf {eff}}$ increases in all cases of auxiliary heating scenarios due to enhanced plasma–wall interaction, accompanied by influx increases of low ionization states of impurities such as C2+ and Fe1+ in plasma edge. Siliconization for wall conditioning is prominently effective in lowering the main impurity influxes in plasma edge and thus the impurity level, and a concentration of ~4% for carbon and ~0.2% for iron is roughly evaluated for a typical nonsiliconized plasma. A simple relationship that $Z_{\mathrm {eff}}$ is positively correlated with $\Phi _{\mathrm {in}}$ and $\tau _{\mathrm {p}}$ is verified from the L - and $H$ -mode features, where $\Phi _{\mathrm {in}}$ is the impurity influx and $\tau _{\mathrm {p}}$ the particle confinement time. A nearly constant $\bar {Z}_{\mathbf {eff}}$ evolution is observed during $L$ – $H$ and $H$ – $L$ transition and it seems that $\bar {Z}_{\mathbf {eff}}$ is insensitive to $L$ – $H$ and $H$ – $L$ transition under some $Z_{\mathrm {eff}}$ (0) threshold. The $Z_{\mathrm {eff}}$ profiles are flat/weakly hollow in plasma core region (rho $Z_{\mathrm {eff}}$ (0) and tend to be peaked when $Z_{\mathrm {eff}}$ (0) is larger than 3, which agrees with the neoclassical theory prediction.

Seed traits determine species' responses to fire under varying soil heating scenarios

Abstract Many plant species in fire‐prone environments maintain persistence through fire via soil seedbanks. However, seeds stored within the soil are at risk of mortality from elevated soil temperatures during fire. Seeds may be protected from fire‐temperature impacts by burial, however, those buried too deeply may germinate but fail to emerge. Thus, successful post‐fire seed regeneration is contingent upon a trade‐off between burial depth and survival through fire. We examined the relationships between seedling emergence behaviour, seed survival and soil temperatures during fire in 13 native and four non‐native woodland species in southwestern Australia. We assessed total seedling emergence per depth, maximum seedling emergence depth and seedling emergence speed from seeds planted at eight depths (0, 1, 2, 3, 4, 5, 7, 10 cm). Soil temperatures were quantified using distributed temperature sensing in optic fibre (DTS), measured continuously between 1 and 10 cm in depth (temperatures were subsequently categorized into 1 cm increments for analysis) during five experimental fires in beds with fine fuels manipulated between 8 and 20 t/ha. Using seed survival and emergence success relative to soil temperatures, we determined vulnerability of seedling emergence relative to soil temperatures generated by combustion of fuel quantities typically observed in woodlands. Maximum depth of emergence varied between species from 2 to &gt;10 cm, with a positive linear correlation to seed mass. Maximum soil temperatures from the two highest fuel masses exceeded seed lethal thresholds (T50—representing temperatures lethal to 50% of seeds) of at least five species. Lethal temperatures were exceeded at all potential emergence depths for all three grass species, and all four non‐native species studied. Of the remaining 10 species, temperatures did not exceed the lethal thresholds under any of the fuel mass levels tested. We found no relationship between lethal temperature thresholds and maximum emergence depth. Our data demonstrate that seeds exhibit variation in their response to soil heating and capacity to emerge from depth, with three distinct functional responses amongst our study species, which enable persistence through, and recruitment following, fire. Such variation in species attributes and fuel mass may lead to heterogeneity (within fires) or divergent trajectories (among fires) in community response under changed fire regime. A free Plain Language Summary can be found within the Supporting Information of this article.

Progress on the small modular stellarator SCR-1: new diagnostics and heating scenarios

This work presents updates in the diagnostics systems, magnetohydrodynamics (MHD) calculations and simulations of microwave heating scenarios of the small modular Stellarator of Costa Rica 1 (SCR-1). Similarly, the design of a flexible bolometer and magnetic diagnostics (a set of Mirnov coils, Rogowski coils and two diamagnetic loops) are introduced. Furthermore, new MHD equilibrium calculations for the plasma of the SCR-1 device were performed using the VMEC code including the poloidal cross-section of the magnetic flux surfaces at different toroidal positions, profiles of the rotational transform, magnetic well, magnetic shear and total magnetic field norm. Charged particle orbits in vacuum magnetic field were computed by the magnetic field solver BS-SOLCTRA (Vargas et al. In 27th IAEA Fusion Energy Conference (FEC 2018), 2018. IAEA). A visualization framework was implemented using Paraview (Solano-Piedra et al. In 23rd IAEA Technical Meeting on the Research Using Small Fusion Devices (23rd TM RUSFD), 2017) and compared with magnetic mapping results (Coto-Vílchez et al. In 16th Latin American Workshop on Plasma Physics (LAWPP), 2017, pp. 43–46). Additionally, simulations of microwave heating scenarios were performed by the IPF-FDMC full-wave code. These simulations calculate the conversion of the ordinary waves to extraordinary waves and allow us to identify the location where the conversion takes place. Finally, the microwave heating scenarios for the $330^{\circ }$ toroidal position are presented. The microwave heating scenarios showed that the O–X–B mode conversion is around 12–14 %. It was possible to identify the spatial zone where the conversion takes place (upper hybrid frequency).

Mathematical modelling and validation of the thermal buoyancy characteristics of a mixed mode natural convection solar crop dryer with back up heater

This paper presents the modelling and subsequent validation of the thermal buoyancy characteristics for an experimental mixed-mode natural convection solar crop dryer (MNCSCDBH) for three plenum inlet opening to vent outlet opening ratios of 1:1, 1:1.3 and 1:1.5 selected for the purpose of this study. The simulation follows the authors’ experimental study on the effect of varying the plenum inlet width and vent outlet width on thermal buoyancy performance of the MNCSCDBH for three different heating scenarios namely; solar heating, back up heating and hybrid heating. Mathematical models, capable of predicting the thermal buoyancy performance of the MNCSCDBH for the three selected heating modes were formulated by coupling energy balance equations on the components of the air-heater with energy balance for the air. The models were based on a one-dimensional steady-state operation of the dryer. A MATLAB code was developed and used to predict the performance of the dryer under no load conditions. The temperature predictions were observed to be accurate within 0.03% to 9.3% for solar heating mode, 0.20% to 7.49% for backup heating mode, and 0.03% to 12.8% for hybrid heating modes, respectively. Even though some discrepancies were found between the experimental performance indicators and their corresponding values predicted by the model as presented in this study, the code can be used in predicting the ventilation performance of the dryer under no load conditions with a general prediction to within 0.03% to 12.8% relative difference of the observed outlet velocity and critical system temperature values. The validation results show that the simulation code can serve as an effective tool for comparing and refining the designs of the MNCSCDBH for optimum drying performance.

Potential environmental benefits of direct electric heating powered by waste-to-energy processes as a replacement of solid-fuel combustion in semi-rural and remote areas

The combustion of wood-based biomass for domestic heating, which is common in rural and mountainous regions of Europe, entails significant local impacts on air quality. Worse conditions occur in low-income countries where the use of coal in household stoves is a common practice. The present paper aims at demonstrating that the combination of waste-to-energy (WtE) plants (based on direct or indirect waste combustion technologies) and direct electric heating (DEH) would be beneficial to reduce air pollution and, meanwhile, optimize the local waste management. Specifically, a WtE plant powering a DEH network will be compared with two reference scenarios of domestic heating: the use of wood/pellet stoves and coal stoves. The results show that shifting to a DEH system, powered by the nearby WtE plant, would reduce the emissions of total suspended particles, NOx, CO, VOCs, dioxins, PAHs and heavy metals by >99%, 27%, 97%, 96%, 93%, 94% and 32%, respectively, with respect to the use of solid fuel in household stoves. In addition, the higher degree of atmospheric dispersion of the off-gas from the stack of the WtE plant is expected to further reduce the impacts in terms of air quality, as estimated by an approach based on the concept of dilution factors. The avoided transportation of waste to other waste facilities outside the region would reduce the greenhouse gas emissions with respect to coal combustion and biomass burning, by 63% and 3%, respectively. The integration of local WtE and DEH could be also “mild”, opening to scenarios that could improve the local air quality without renouncing totally to the habits of domestic wood combustion in mountainous regions. Mild-DEH could be designed to integrate the domestic use of wood with electrical heaters, reducing fuel use and air pollution.

Observation and Modeling of High-temperature Solar Active Region Emission during the High-resolution Coronal Imager Flight of 2018 May 29

Abstract Excellent coordinated observations of NOAA active region 12712 were obtained during the flight of the High-resolution Coronal Imager (Hi-C) sounding rocket on 2018 May 29. This region displayed a typical active region core structure with relatively short, high-temperature loops crossing the polarity inversion line and bright “moss” located at the footpoints of these loops. The differential emission measure (DEM) in the active region core is very sharply peaked at about 4 MK. Further, there is little evidence for impulsive heating events in the moss, even at the high spatial resolution and cadence of Hi-C. This suggests that active region core heating is occurring at a high frequency and keeping the loops close to equilibrium. To create a time-dependent simulation of the active region core, we combine nonlinear force-free extrapolations of the measured magnetic field with a heating rate that is dependent on the field strength and loop length and has a Poisson waiting time distribution. We use the approximate solutions to the hydrodynamic loop equations to simulate the full ensemble of active region core loops for a range of heating parameters. In all cases, we find that high-frequency heating provides the best match to the observed DEM. For selected field lines, we solve the full hydrodynamic loop equations, including radiative transfer in the chromosphere, to simulate transition region and chromospheric emission. We find that for heating scenarios consistent with the DEM, classical signatures of energy release, such as transition region brightenings and chromospheric evaporation, are weak, suggesting that they would be difficult to detect.