Efficient lower hybrid current drive (LHCD) is demonstrated at densities up to nover ¯_{e}≈1.5×10^{20} m^{-3} in diverted plasmas on the Alcator C-Mod tokamak by operating at increased plasma ...current-and therefore reduced Greenwald density fraction. This density exceeds the nominal "LH density limit" at nover ¯_{e}≈1.0×10^{20} m^{-3} reported previously, above which an anomalous loss of current drive efficiency was observed. The recovery of current drive efficiency to a level consistent with engineering scalings is correlated with a reduction in density shoulders and turbulence levels in the far scrape-off layer. Concurrently, rf wave interaction with the edge and/or scrape-off-layer plasma is reduced, as indicated by a minimal broadening of the wave frequency spectrum measured at the plasma edge. These results have important implications for sustaining steady-state tokamak operation and indicate a pathway forward for implementing efficient LHCD in a reactor.
Overview of the SPARC tokamak Creely, A. J.; Greenwald, M. J.; Ballinger, S. B. ...
Journal of plasma physics,
10/2020, Letnik:
86, Številka:
5
Journal Article
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The SPARC tokamak is a critical next step towards commercial fusion energy. SPARC is designed as a high-field ($B_0 = 12.2$ T), compact ($R_0 = 1.85$ m, $a = 0.57$ m), superconducting, D-T tokamak ...with the goal of producing fusion gain $Q>2$ from a magnetically confined fusion plasma for the first time. Currently under design, SPARC will continue the high-field path of the Alcator series of tokamaks, utilizing new magnets based on rare earth barium copper oxide high-temperature superconductors to achieve high performance in a compact device. The goal of $Q>2$ is achievable with conservative physics assumptions ($H_{98,y2} = 0.7$) and, with the nominal assumption of $H_{98,y2} = 1$, SPARC is projected to attain $Q \approx 11$ and $P_{\textrm {fusion}} \approx 140$ MW. SPARC will therefore constitute a unique platform for burning plasma physics research with high density ($\langle n_{e} \rangle \approx 3 \times 10^{20}\ \textrm {m}^{-3}$), high temperature ($\langle T_e \rangle \approx 7$ keV) and high power density ($P_{\textrm {fusion}}/V_{\textrm {plasma}} \approx 7\ \textrm {MW}\,\textrm {m}^{-3}$) relevant to fusion power plants. SPARC's place in the path to commercial fusion energy, its parameters and the current status of SPARC design work are presented. This work also describes the basis for global performance projections and summarizes some of the physics analysis that is presented in greater detail in the companion articles of this collection.
BackgroundSensenbrenner syndrome is a heterogeneous ciliopathy that is characterised by skeletal and ectodermal anomalies, accompanied by chronic renal failure, heart defects, liver fibrosis and ...other features.ObjectiveTo identify an additional causative gene in Sensenbrenner syndrome.MethodsSingle nucleotide polymorphism array analysis and standard sequencing techniques were applied to identify the causative gene. The effect of the identified mutation on protein translation was determined by western blot analysis. Antibodies against intraflagellar transport (IFT) proteins were used in ciliated fibroblast cell lines to investigate the molecular consequences of the mutation on ciliary transport.ResultsHomozygosity mapping and positional candidate gene sequence analysis were performed in two siblings with Sensenbrenner syndrome of a consanguineous Moroccan family. In both siblings, a homozygous mutation in the initiation codon of C14ORF179 was identified. C14ORF179 encodes IFT43, a subunit of the IFT complex A (IFT-A) machinery of primary cilia. Western blots showed that the mutation disturbs translation of IFT43, inducing the initiation of translation of a shorter protein product from a downstream ATG. The IFT-A protein complex is implicated in retrograde ciliary transport along axonemal microtubules. It was shown that in fibroblasts of one of the siblings affected by Sensenbrenner syndrome, disruption of IFT43 disturbs this transport from the ciliary tip to its base. As anterograde transport in the opposite direction apparently remains functional, the IFT complex B proteins accumulate in the ciliary tip. Interestingly, similar results were obtained using fibroblasts from a patient with Sensenbrenner syndrome with mutations in WDR35/IFT121, encoding another IFT-A subunit.ConclusionsThe results indicate that Sensenbrenner syndrome is caused by disrupted IFT-A-mediated retrograde ciliary transport.
Micro- and nanoplastics have been detected in environmental compartments from the highest mountains to the deepest seas. They have been shown to be present at almost all trophic levels, and within ...humans they have been detected in numerous organs and human stool. Whilst their ubiquitous nature is indisputable, little is known about the health risks they may present. Much current research is focussed on the production of test materials with which to perform the necessary health studies. An important aspect of this is the correct storage and suspension of the materials to ensure they remain stable both chemically and with regards to size and shape. In this review, we look at the chemical stability of nine common polymers in a range of liquids; first with the use of commercial compatibility charts and then with a more quantitative approach using Hansen solubility parameters. We then look at stability with regards to particle agglomeration, whether and how stable compositions can be predicted, and which dispersants can be added to increase stability. Finally, we discuss the role of bio-surfactants and the eco-corona and how these may offer a route to both better stability and environmental relevance.
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•No “one size fits all” approach, different plastic types require different liquids.•Zeta potential and Hansen Solubility Parameter can predict stable suspensions.•Surfactants aid suspension stability but influence toxicity and uptake tests.•Biosurfactants may aid stability whilst also increasing environmental relevance.
Several plant pathogenic Parastagonospora species have been identified infecting wheat and other cereals over the past 50 years. As new lineages were discovered, naming conventions grew unwieldy and ...the relationships with previously recognized species remained unclear. We used genome sequencing to clarify relationships among these species and provided new names for most of these species. Six of the nine described Parastagonospora species were recovered from wheat, with five of these species coming from Iran. Genome sequences revealed that three strains thought to be hybrids between P. nodorum and P. pseudonodorum were not actually hybrids, but rather represented rare gene introgressions between those species. Our data are consistent with the hypothesis that P. nodorum originated as a pathogen of wild grasses in the Fertile Crescent, then emerged as a wheat pathogen via host-tracking during the domestication of wheat in the same region. The discovery of a diverse array of Parastagonospora species infecting wheat in Iran suggests that new wheat pathogens could emerge from this region in the future.
•The ARC conceptual design study has been extended to include a divertor.•Long legged X-point target divertors are implemented with no impact on core plasma.•All superconducting coils are shielded ...and the tritium breeding ratio is ≈1.08.•An ITER-like tungsten swirl-tube cooling channel with molten FLiBe coolant is used.•The ARC reactor divertor design simplifies detachment control and diagnostics.
The ARC pilot plant conceptual design study has been extended beyond its initial scope B. N. Sorbom et al., FED 100 (2015) 378 to explore options for managing ∼525 MW of fusion power generated in a compact, high field (B0 = 9.2 T) tokamak that is approximately the size of JET (R0 = 3.3 m). Taking advantage of ARC’s novel design – demountable high temperature superconductor toroidal field (TF) magnets, poloidal magnetic field coils located inside the TF, and vacuum vessel (VV) immersed in molten salt FLiBe blanket – this follow-on study has identified innovative and potentially robust power exhaust management solutions. The superconducting poloidal field coil set has been reconfigured to produce double-null plasma equilibria with a long-leg X-point target divertor geometry. This design choice is motivated by recent modeling which indicates that such configurations enhance power handling and may attain a passively-stable detachment front that stays in the divertor leg over a wide power exhaust window. A modified VV accommodates the divertor legs while retaining the original core plasma volume and TF magnet size. The molten salt FLiBe blanket adequately shields all superconductors, functions as an efficient tritium breeder, and, with augmented forced flow loops, serves as an effective single-phase, low-pressure coolant for the divertor, VV, and breeding blanket. Advanced neutron transport calculations (MCNP) indicate a tritium breeding ratio of ∼1.08. The neutron damage rate (DPA/year) of the remote divertor targets is ∼3–30 times lower than that of the first wall. The entire VV (including divertor and first wall) can tolerate high damage rates since the demountable TF magnets allow the VV to be replaced every 1–2 years as a single unit, employing a vertical maintenance scheme. A tungsten swirl tube FLiBe coolant channel design, similar in geometry to that used by ITER, is considered for the divertor heat removal and shown capable of exhausting divertor heat flux levels of up to 12 MW/m2. Several novel, neutron tolerant diagnostics are explored for sensing power exhaust and for providing feedback control of divertor conditions over long time scales. These include measurement of Cherenkov radiation emitted in FLiBe to infer DT fusion reaction rate, measurement of divertor detachment front locations in the divertor legs with microwave interferometry, and monitoring “hotspots” on the divertor chamber walls via IR imaging through the FLiBe blanket.
This paper reports an analysis of the properties of polymer light‐emitting devices (PLEDs) doped with iridium complexes. Devices based on charged and neutral complexes doped into poly(vinylcarbazole) ...(PVK) are presented, and the role of the ions and the charge‐transport properties of the complexes are discussed. In devices with the charged complexes, the concentration of the complex is found to have a profound effect on both the switch‐on voltage and the efficiency. At higher doping concentrations the efficiency is increased and the switch‐on voltage decreased. The increase in efficiency and decrease in switch‐on voltage at higher dopant concentration are found to be due to an alternative charge transport path via the iridium dopant Ir(bpy)+ (bis(2‐phenylpyridine‐C2,N′)(2,2′‐bipyridine)iridium hexafluorophosphate). However, at lower concentrations the complex becomes an electron trap and the efficiency is reduced. The devices are found to be significantly less efficient than those with neutral complexes. This difference is attributed to the ionic content and the charge trapping properties of the charged complexes. The low efficiency of the charged‐complex‐based devices could be overcome by utilizing a hole‐blocking layer; devices with efficiencies as high as 23 cd A–1 were obtained.
Devices based on charged and neutral iridium complexes doped into poly(vinylcarbazole) are presented (see Figure). The role of the ions and the charge‐transport properties of the complexes are discussed. The charged complexes fulfil a double function as emitter and charge transporter.
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