Tokamak Energy (United Kingdom)

Abstract Antihypertensive treatment significantly reduces the risk of cardiovascular mortality in patients with hypertension; however, treatment effects are weaker on cardiac mortality than on cerebrovascular mortality, even with equivalent blood pressure reduction. A potential cause of this difference is the activation of neurohumoral factors; however, few studies have addressed this gap. Therefore, in this study, we evaluated the effectiveness of a combination therapy prioritizing angiotensin-converting enzyme inhibitors and beta-blockers in reducing cardiac mortality in outpatients with hypertension. The retrospective observational cohort study spanned 30 years (1987–2016) at a single institution. From 1992 to 2001, we prioritized the use of a combination of angiotensin-converting enzyme inhibitors and beta-blockers to suppress neurohumoral factors, with calcium channel blockers and diuretics used as supplementary treatments. We tracked the standardized mortality ratios for all-cause, cardiac, and cerebrovascular mortality during each period. Using national data, we retrospectively compared the trends in all-cause and cardiovascular mortality rates in our region with those of the Japanese population. The standardized mortality ratios for all-cause and cardiac mortality in our region decreased significantly from 1992 to 2016 (that is, after treatment initiation) and were significantly lower than national averages after the initial control period. These findings suggest that antihypertensive therapy prioritizing the combination of angiotensin-converting enzyme inhibitors and beta-blockers may contribute to a reduction in cardiac mortality. Future prospective, randomized, double-blind controlled trials are crucial for validating this hypothesis.

Abstract Fusion by Advanced Superconducting Tokamak (FAST) is a project being proposed as a facility for R&D, testing, and demonstration of systems integration for a deuterium–tritium (DT) fusion energy reactor. The required specifications for FAST are: DT fusion power of 50– 100 MW , neutron wall loading of 0.3– 1 MWm − 2 , discharge duration of 1000 s, and full-power operation lifetime of 1000 h. A quasi-zero-dimensional parameter survey has been carried out to find the parameter region necessary to satisfy the above specifications with the minimum device cost. It was found that a low aspect ratio ( A ∼ 2.3 ), compact (major radius ∼ 2.0 m ) tokamak with high temperature superconductor magnets and neutral beam injection power of about 50 MW (with the energy of 500 keV) offers a possible design point. A time-dependent transport analysis was performed to confirm accessibility to such an operating point and to evaluate the required flux swing for the central solenoid.

We present a single-fluid approach for the simulation of partially-ionized plasmas (PIPs), which is designed to capture the non-ideal effects introduced by neutrals while maintaining computational efficiency close to that of single-fluid magnetohydrodynamic (MHD). This is achieved using a model that treats the entire partially ionized plasma as a single mixture, which renders internal ionization/recombination source terms unnecessary as both the charged and neutral species are part of the mixture’s conservative system. Instead, the effects of ionization and the differing physics of the species are encapsulated as material properties of the mixture. Furthermore, the differing dynamics between the charged and neutral species are captured using a relative-velocity quantity, which impacts the bulk behavior of the mixture in a manner similar to the treatment of the ion-electron relative-velocity as current in MHD. Unlike fully-ionized plasmas, the species composition of a PIP changes rapidly with its thermodynamic state. This is captured through a look-up table referred to as the tabulated equation of state (TabEoS), which is constructed prior to runtime using empirical physicochemical databases and efficiently provides the ionization fraction and other material properties of the PIP specific to the thermodynamic state of each computational cell. Crucially, the use of TabEoS also allows our approach to self-consistently capture the non-linear feedback cycle between the PIP’s macroscopic behavior and the microscopic physics of its internal particles, which is neglected in many fluid simulations of plasmas today.

Abstract An experimental scan of the electron cyclotron waves (EC) toroidal injection angle in plasma breakdown is performed at the DIII-D tokamak. The second harmonic, extraordinary mode EC is used for the study. The dependence of n e and T e on the EC injection angle cannot be conclusively drawn from this study due to the large error bars in the n e and T e measurements. On the other hand, high T e data points are observed in some discharges which can be explained by nonlinear heating. The D α emission measurement shows a clear relation between the breakdown time and the injection angle. An experimental investigation of the cause of the dependence of breakdown delay on the EC injection angle suggests that when the injection angle is oblique, the EC heating after the reflection at the inboard wall may become ineffective and cause the breakdown delay even when the EC heating before and directly upon injection remains effective. A preliminary run of the heat and transport balance code DYON indicates that the obtained dataset is suitable for a quantitative validation of EC absorption models.

Abstract The publication provide further insights into the dynamics of JET runaway electron (RE) beams mitigated by D2-rich shattered pellet injection (SPI) (Reux et al 2022 Plasma Phys. Control. Fusion 64 034002). Multi-diagnostic analyses show that mechanisms causing continuous RE losses and energy transfer from hot electrons to cold background plasma can act before the SPI. After the SPI, measurements are compatible with a reduction of the maximum energy and pitch angle of the RE distribution while the population of supra-thermal electrons increases. The RE population growth is likely due to electron avalanche. Dark island-like pattern chains, characterised by an integer poloidal mode number and a certain minor radius, are identified in the JET RE beam synchrotron radiation videos. The synchrotron island dynamics is studied via a newly developed computer vision code (Sommariva and Silburn https://c4science.ch/source/pSpiPTV/). The radial motion of synchrotron island chains is found to be consistent with the most plausible time evolution of the radial current density profile compatible with both the RE synchrotron videos and the total RE current time trace. Similarly, correlations are identified between the temporal progression of the synchrotron islands poloidal rotation frequency and sudden MHD relaxation events. Loss-of-RE events probably caused by non-linear interactions between synchrotron islands are observed for the first time. Experimental evidences suggest that synchrotron islands are possibly related to the existence of magnetic islands which may lead to the development of new RE beam mitigation strategies.

Plasma facing components (PFCs) in the next generation of tokamak devices will operate in challenging environments, with heat loads predicted to exceed 10 MWm$^{-2}$. The magnitude of these heat loads is set by the width of the channel, the "scrape-off layer" (SOL), into which heat is exhausted, and can be characterised by an e-folding length scale for the decay of heat flux across the channel. It is expected this channel will narrow as tokamaks move towards reactor relevant conditions. Understanding the processes involved in setting the SOL heat flux width is imperative to be able to predict the heat loads PFCs must handle in future devices. Measurements of the SOL width are performed on the high-field spherical tokamak, ST40, using a newly commissioned infrared thermography system. With its high on-axis toroidal magnetic field ($\geq$1.5 T) ST40 is uniquely positioned to investigate the influence of toroidal field on the heat flux width in spherical tokamaks, whilst also extending measurements of the SOL width in spherical tokamaks to increased poloidal field ($\geq$0.3 T). Due to the divertor on ST40 having a low degree of axisymmetry, it is necessary for a set of radial measurements of the heat flux to be taken across the divertor, made possible using an automated toolchain that fully incorporates its 3D geometry. These radial profiles are combined with the magnetic topology of the plasma to infer the width of the SOL, with both single and double exponential profiles of heat flux observed. A reduction in the heat flux is observed toroidally across part of the divertor, with preliminary investigations indicating that partial shadowing occurs, resulting from the separation between magnetic field lines and trailing edges upstream of the observed region becoming comparable to the ion gyro-radius.

The scrape-off layer parallel heat flux decay lengths measured at ST40, a high field, low aspect ratio spherical tokamak, have been observed to bifurcate into two groups. The wide group matches closely with the scale of ion poloidal Larmour radius and follows existing H-mode scalings, while the narrow group falls up to 10 times below scalings, on the scale of ion total Larmour radius. The onset of the narrow scrape-off layer width is observed to be associated with suppressed magnetic fluctuations, suggesting reduced electromagnetic turbulence levels in the SOL.

Material issues pose a significant challenge for the design of future fusion reactors. These issues require new advanced materials to be developed. W‐fiber‐reinforced W‐composite material (W f/W) incorporates extrinsic toughening mechanisms increasing the resistance against failure and thus granting steps toward application in a future fusion reactor. W f/W can be produced based on chemical vapor deposition or powder metallurgical routes. In this contribution, the efforts of upscaling the production of W f/W will be reviewed based on recent results. In addition, the activities related to enabling large‐scale production for new fusion applications are being studied. Herein, two main achievements are to be highlighted. First, an upscaled production is established to produce flat tile samples for joining tests on copper and steel, and second, a new method of joining W f/W on copper is established and tested under high heat‐flux conditions.