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Nuclear fusion is entering the era of power plant-scale devices, which are now undergoing extensive studies to support the design phase. Plasma disruptions pose a high risk to these classes of devices because of the large stored thermal and magnetic energy which might jeopardize machine integrity and availability. Therefore, disruptions within these devices must be virtually eliminated, and any disruptions which do happen must be highly mitigated. However, the characterisation, prediction and technology used to mitigate disruptions is still an area of active development. In this paper, the authors investigate the disruptions within ST40, with particular attention at the identification of causes and effects associated with disruptions, both from a physics basis and an engineering standpoint. This paper aims at presenting preliminary predictive analyses of ST40 plasma scenarios by exploiting Machine Learning techniques applied to an experimental database populated by plasma pulses executed during the ST40 2021–2022 experimental campaign. The database contains both disrupted and non-disrupted pulses. Using Machine Learning, common features within disruptions are automatically classified and identified, mapping the controllable operational space in terms of plasma displacement and variation of specific plasma internal parameters. The classification was validated by benchmarking the numerical reconstruction of the plasma dynamics with experimental data recovered from the plasma diagnostics. Subsequent Machine Learning analyses allowed the extrapolation of new disrupted plasma configurations for preliminary predictive simulations of the plasma column displacement. Thanks to the numerical simulations performed in MAXFEA environment, it is possible to investigate the plasma vertical displacement both during disrupted and regularly terminated plasma scenarios and to provide lessons to be learnt for the next ST40 experimental campaign and for the design of future ST devices. [ABSTRACT FROM AUTHOR]

Abstract Nuclear fusion is entering the era of power plant-scale devices, which are now undergoing extensive studies to support the design phase. Plasma disruptions pose a high risk to these classes of devices because of the large stored thermal and magnetic energy which might jeopardize machine integrity and availability. Therefore, disruptions within these devices must be virtually eliminated, and any disruptions which do happen must be highly mitigated. However, the characterisation, prediction and technology used to mitigate disruptions is still an area of active development. In this paper, the authors investigate the disruptions within ST40, with particular attention at the identification of causes and effects associated with disruptions, both from a physics basis and an engineering standpoint. This paper aims at presenting preliminary predictive analyses of ST40 plasma scenarios by exploiting Machine Learning techniques applied to an experimental database populated by plasma pulses executed during the ST40 2021–2022 experimental campaign. The database contains both disrupted and non-disrupted pulses. Using Machine Learning, common features within disruptions are automatically classified and identified, mapping the controllable operational space in terms of plasma displacement and variation of specific plasma internal parameters. The classification was validated by benchmarking the numerical reconstruction of the plasma dynamics with experimental data recovered from the plasma diagnostics. Subsequent Machine Learning analyses allowed the extrapolation of new disrupted plasma configurations for preliminary predictive simulations of the plasma column displacement. Thanks to the numerical simulations performed in MAXFEA environment, it is possible to investigate the plasma vertical displacement both during disrupted and regularly terminated plasma scenarios and to provide lessons to be learnt for the next ST40 experimental campaign and for the design of future ST devices.

The Heat Flux Engineering Analysis Toolkit (HEAT) (Looby et al., 2022) was used to simulate the heat flux, qtarget, on ST40 molybdenum divertors. Results were compared with experimental infrared (IR) data. Two shots, 11419 and 11376 at time instants 119 ms and 120 ms, with lower-biased disconnected double null geometries, were studied. Single-λ and multi-λ heat flux profiles were used as input in HEAT simulation. The simulated qtarget was used in OpenFOAM to calculate the corresponding temperature, T, on the divertors. Results showed that a good agreement on the simulated qtarget, T and shape of the heat flux on the divertor with the IR data was achieved when a multi-λ heat flux profile was used for 11419, and single-λ heat flux profile for 11376. This indicates that HEAT can be reliable in analyzing and understanding the heat loading of plasma facing components in tokamak devices.

Salmonella enterica serovar Derby (S. Derby) ranks fifth among nontyphoidal Salmonella serovars causing human infections in the European Union. S. Derby isolates (36) collected between 2006 and 2018 in a Spanish region (Asturias) from human clinical samples (20) as well as from pig carcasses, pork- or pork and beef-derived products, or wild boar (16) were phenotypically characterized with regard to resistance, and 22 (12 derived from humans and 10 from food-related samples) were also subjected to whole genome sequence analysis. The sequenced isolates belonged to ST40, a common S. Derby sequence type, and were positive for SPI-23, a Salmonella pathogenicity island involved in adherence and invasion of the porcine jejune enterocytes. Isolates were either susceptible (30.6%), or resistant to one or more of the 19 antibiotics tested for (69.4%). Resistances to tetracycline [tet(A), tet(B) and tet(C)], streptomycin (aadA2), sulfonamides (sul1), nalidixic acid [gyrA (Asp87 to Asn)] and ampicillin (blaTEM-1-like) were detected, with frequencies ranging from 8.3% to 66.7%, and were higher in clinical than in food-borne isolates. The fosA7.3 gene was present in all sequenced isolates. The most common phenotype was that conferred by the tet(A), aadA2 and sul1 genes, located within identical or closely related variants of Salmonella Genomic Island 1 (SGI1), where mercury resistance genes were also present. Diverse IncI1-I(α) plasmids belonging to distinct STs provided antibiotic [blaTEM-1, tet(A) and/or tet(B)] and heavy metal resistance genes (copper and silver), while small pSC101-like plasmids carried tet(C). Regardless of their location, most resistance genes were associated with genetic elements involved in DNA mobility, including a class one integron, multiple insertion sequences and several intact or truncated transposons. By phylogenetic analysis, the isolates were distributed into two distinct clades, both including food-borne and clinical isolates. One of these clades included all SGI1-like positive isolates, which were found in both kinds of samples throughout the entire period of study. Although the frequency of S. Derby in Asturias was very low (0.5% and 3.1% of the total clinical and food isolates of S. enterica recovered along the period of study), it still represents a burden to human health linked to transmission across the food chain. The information generated in the present study can support further epidemiological surveillance aimed to control this zoonotic pathogen. [ABSTRACT FROM AUTHOR]

ST40 is a compact, high-field ( $B_{\mathrm{T0}}\unicode{x2A7D} 2.1\,\,\,\textrm{T}$ ) spherical tokamak (ST) with a mission to expand the physics and technology basis for the ST route to commercial fusion. The ST40 research programme covers confinement and stability; solenoid-free start-up; high-performance operating scenarios; and plasma exhaust. In 2022, ST40 obtained central deuterium ion temperatures of $9.6 \pm 0.4\ \textrm{keV}$ , demonstrating for the first time that pilot plant relevant ion temperatures can be reached in a compact, high-field ST. Analysis of these high-ion temperature plasmas is presented, including a summary of confinement, transport and microstability characteristics, and energetic particle instabilities. Recent scenario development activities have focused on establishing diverted H-mode plasmas across a range of toroidal fields and plasma currents, along with scenarios with high non-inductive current fractions. In future operations, beginning in 2025, a 1 MW dual frequency (104/137 GHz) electron cyclotron (EC) system will be installed to enable the study of EC and electron Bernstein wave plasma start-up and current drive. Predictive modelling of the potential performance of these systems is presented.

The GLOBSYS code was developed for analysis and prediction of parameters of the Globus-M2 tokamak and its modifications. In [1], preliminary selection of correlations which connect physical and technical parameters was made. In this paper, the verification of the code using the achieved and predicted data from the installations NSTX, NSTX-U, MAST, MAST-U, and ST40 is given. As a whole, there is good agreement between simulations and plasma parameters at the discharge plateau. The best agreement is observed if ITER confinement scaling is used for energy confinement time with the enhancement factor Hy, 2 = 1–1.2. Simulations with other confinement scalings (Globus-2021, NSTX scalings) give good agreement with plasma parameters for the toroidal field Bt0 ~ 0.5 T. For increasing Bt0, more optimistic predicted plasma parameters are obtained for the Globus-2021 and NSTX scalings in comparison with the ITER confinement scaling. The condition of reaching the plasma quasistationary regime (or the time of establishment of quasistationary plasma profiles τL/R) is estimated for NSTX, NSTX-U, MAST, MAST-U and ST40 discharges. This time is compared with two technical restrictions, which are connected with the times of toroidal field coil heating and poloidal flux capacity. Verification of the GLOBSYS code using the data from the aforementioned spherical tokamaks is the basis for the prediction of parameters of the next step of Globus-M program. [ABSTRACT FROM AUTHOR]

Salmonella enterica serovar Derby (S. Derby) ranks fifth among nontyphoidal Salmonella serovars causing human infections in the European Union. S. Derby isolates (36) collected between 2006 and 2018 in a Spanish region (Asturias) from human clinical samples (20) as well as from pig carcasses, pork- or pork and beef-derived products, or wild boar (16) were phenotypically characterized with regard to resistance, and 22 (12 derived from humans and 10 from food-related samples) were also subjected to whole genome sequence analysis. The sequenced isolates belonged to ST40, a common S. Derby sequence type, and were positive for SPI-23, a Salmonella pathogenicity island involved in adherence and invasion of the porcine jejune enterocytes. Isolates were either susceptible (30.6%), or resistant to one or more of the 19 antibiotics tested for (69.4%). Resistances to tetracycline [tet(A), tet(B) and tet(C)], streptomycin (aadA2), sulfonamides (sul1), nalidixic acid [gyrA (Asp87 to Asn)] and ampicillin (blaTEM-1-like) were detected, with frequencies ranging from 8.3% to 66.7%, and were higher in clinical than in food-borne isolates. The fosA7.3 gene was present in all sequenced isolates. The most common phenotype was that conferred by the tet(A), aadA2 and sul1 genes, located within identical or closely related variants of Salmonella Genomic Island 1 (SGI1), where mercury resistance genes were also present. Diverse IncI1-I(α) plasmids belonging to distinct STs provided antibiotic [blaTEM-1, tet(A) and/or tet(B)] and heavy metal resistance genes (copper and silver), while small pSC101-like plasmids carried tet(C). Regardless of their location, most resistance genes were associated with genetic elements involved in DNA mobility, including a class one integron, multiple insertion sequences and several intact or truncated transposons. By phylogenetic analysis, the isolates were distributed into two distinct clades, both including food-borne and clinical isolates. One of these clades included all SGI1-like positive isolates, which were found in both kinds of samples throughout the entire period of study. Although the frequency of S. Derby in Asturias was very low (0.5% and 3.1% of the total clinical and food isolates of S. enterica recovered along the period of study), it still represents a burden to human health linked to transmission across the food chain. The information generated in the present study can support further epidemiological surveillance aimed to control this zoonotic pathogen.

Salmonella is a foodborne pathogen that poses a severe public health threat. Salmonella enterica serovar Derby (S. Derby) is one of the top five serovars isolated from humans and animals, and it carries the potential risk of transmission to humans through consumption of pork and related products. This study isolated 98 S. Derby, mainly from pork, and clinical samples in Guangdong to investigate and compare their molecular characteristics, phylogenetic relationships, transmission routes, antimicrobial resistance phenotypes, genotypes, and virulence profiles. Whole-genome sequencing (WGS) revealed that all S. Derby isolates belonged to ST40 and displayed a relatively large core genome. Phylogenomic analysis indicated the possibility of clonal transmission of S. Derby not only between pork and humans but also across geographic areas in Guangdong over an extended period of time. Discriminant analysis of principal components (DAPC) model showed that a significant proportion of S. Derby isolates retrieved from multiple hosts originated from pork. Furthermore, similar antimicrobial resistance phenotypes and genotypes were found in S. Derby strains recovered from animal products and humans. All S. Derby isolates were found to contain numerous virulence genes, primarily related to fimbrial adherence determinants and secretion system components. This study offers valuable insights into the transmission routes of S. Derby between pork and humans and provides essential data for public health management. • Clonal transmission of S. Derby is a possibility cross-host and cross-geographical. • A large proportion of S. Derby from human originated from pork. • Similar antimicrobial resistance was observed in S. Derby from pork and human. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the prevalence of fosfomycin fosA7 in Salmonella enterica isolates from food animals and retail meat products in China and the impact of fosA7 on bacterial fitness. A total of 360 Salmonella isolates collected from 11 provinces and cities in China were detected for fosA7. All fosA7 -positive Salmonella isolates were determined minimum inhibitory concentrations (MICs) and sequenced by Illumina Hiseq. The fosA7 gene of S. Derby isolate HA2-WA5 was knocked out. The full length of fosA7 was cloned into vector pBR322 and then transformed into various hosts. MICs of fosfomycin, growth curves, stability, and fitness of fosA7 were evaluated. The fosA7 gene was identified in S. Derby (ST40, n = 30) and S. Reading (ST1628, n = 5). MICs to fosfomycin of 35 fosA7 -positive isolates were 1 to 32 mg/L. All fosA7 were located on chromosomes of Salmonella. The deletion of fosA7 in HA2-WA5 decreased fosfomycin MIC by 16-fold and slightly affected its fitness. The acquisition of plasmid-borne fosA7 enhanced MICs of fosfomycin in Salmonella (1,024-fold) and Escherichia coli (16-fold). The recombinant plasmid pBR322- fosA7 was stable in Salmonella Typhimurium, S. Pullorum, S. Derby, and E. coli , except for Salmonella Enteritidis, and barely affected on the growth of them but significantly increased biological fitness in Salmonella. The spread of specific Salmonella serovars such as S. Derby ST40 will facilitate the dissemination of fosA7. fosA7 can confer high-level fosfomycin resistance and enhance bacterial fitness in Salmonella if transferred on plasmids; thus, it has the potential to be a reservoir of the mobilized fosfomycin resistance gene. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the prevalence of fosfomycin fosA7 in Salmonella enterica isolates from food animals and retail meat products in China and the impact of fosA7 on bacterial fitness. A total of 360 Salmonella isolates collected from 11 provinces and cities in China were detected for fosA7. All fosA7-positive Salmonella isolates were determined minimum inhibitory concentrations (MICs) and sequenced by Illumina Hiseq. The fosA7 gene of S. Derby isolate HA2-WA5 was knocked out. The full length of fosA7 was cloned into vector pBR322 and then transformed into various hosts. MICs of fosfomycin, growth curves, stability, and fitness of fosA7 were evaluated. The fosA7 gene was identified in S. Derby (ST40, n = 30) and S. Reading (ST1628, n = 5). MICs to fosfomycin of 35 fosA7-positive isolates were 1 to 32 mg/L. All fosA7 were located on chromosomes of Salmonella. The deletion of fosA7 in HA2-WA5 decreased fosfomycin MIC by 16-fold and slightly affected its fitness. The acquisition of plasmid-borne fosA7 enhanced MICs of fosfomycin in Salmonella (1,024-fold) and Escherichia coli (16-fold). The recombinant plasmid pBR322-fosA7 was stable in Salmonella Typhimurium, S. Pullorum, S. Derby, and E. coli, except for Salmonella Enteritidis, and barely affected on the growth of them but significantly increased biological fitness in Salmonella. The spread of specific Salmonella serovars such as S. Derby ST40 will facilitate the dissemination of fosA7. fosA7 can confer high-level fosfomycin resistance and enhance bacterial fitness in Salmonella if transferred on plasmids; thus, it has the potential to be a reservoir of the mobilized fosfomycin resistance gene.

Ion temperatures of over 100 million degrees Kelvin (8.6 keV) have been produced in the ST40 compact high-field spherical tokamak (ST). Ion temperatures in excess of 5 keV have not previously been reached in any ST and have only been obtained in much larger devices with substantially more plasma heating power. The corresponding fusion triple product is calculated to be ${n_{i0}}{T_{i0}}{\tau _E} \approx 6 \pm 2 \times {10^{18}}{{\text{m}}^{ - 3}}{\text{keVs}}$ . These results demonstrate for the first time that ion temperatures relevant for commercial magnetic confinement fusion can be obtained in a compact high-field ST and bode well for fusion power plants based on the high-field ST.

Linear and nonlinear perturbative analyses of low-frequency instabilities are presented for ST40 spherical torus high field plasmas, with simultaneous neutral beam heating due to two tangential sources at 25 keV and 55 keV. Initial plasma profiles on which the TRANSP and NUBEAM codes were based were obtained using an integrated analysis of several diagnostics including line-of-sight integrated and volume average measurements, as well as limited profile information from a charge-exchange-recombination spectrometer. Magnetohydrodynamics (MHD) analysis using the NOVA/NOVA-K codes suggests that the modes in the experiments are core-localized n = 1 eigenmodes with mixed acoustic and electromagnetic Alfvénic polarization. The global transport combined with the perturbative mode analysis indicates that there is greater tendency for bursty chirping response as the level of background micro-turbulence decreases in time and those predictions are shown to be consistent with the experimental data. This finding is interpreted in terms of the suppression of coherent phase-space structures that support chirping when the resonant fast ion dynamics is dominated by frequent stochastic, orbit-decorrelating events.

Merging compression is an efficient and robust method for plasma start-up which can achieve both high plasma current and high temperatures at fusion relevant densities. It involves the formation of plasma around two in-vessel poloidal field coils followed by a magnetic reconnection event after which the plasma can be compressed. In this paper we extrapolate from START/MAST experimental data to predict the performance of ST40 (currently under construction). In our analysis we found that induced eddy currents within passive elements greatly affected the scenario. [ABSTRACT FROM AUTHOR]

Orbit following Monte Carlo code (ASCOT) calculations of neutral beam (NB) induced torque, current and heating have been performed for a selected set of plasma scenarios to optimise the neutral beam injection system for the proposed high magnetic field spherical tokamak ST40. It is found that there are strong variations especially in the current drive efficiency and in the toroidal torque depending on the NB alignment and injection energy. The optimal alignments as well as the optimal injection energy depend both on the scenario and whether the current drive or the toroidal torque is to be maximised. Due to the relatively small calculated current drive efficiency (0.05–0.2 MA/MW) we find that for the studied scenarios a relatively central low field side (LFS) deposition below midplane provides the best overall performance still at a tolerable shine through power. [ABSTRACT FROM AUTHOR]

• Study the global and the local stress state generated on the IVC2, on its supports and on all the components that weigh on it. • Application of a highly detailed multi-body FEM model to accurately approximate the ST40 structural behavior. • Evaluating the advantages of using ANSYS Workbench in combination with ANSYS APDL code and ANSA Pre-processor to automatically define contacts and to parametrize the joint elements to the variation of the mesh. The paper aims to define the structural behavior of the ST40 Inner Vacuum Chamber (IVC2) under the action of electromagnetic loads from a previously analysed plasma disruption scenario, namely an Upward Vertical Displacement Event (UVDE) scenario. This spherical tokamak is owned by Tokamak Energy Ltd, and it is the highest field device of its kind. The considered loads are obtained from a previous electromagnetic analysis [1] and interpolated on the structural model. Indeed, the study represents the second and final part of the IVC2 electromagnetic and structural behavior characterization. The maximum load due to eddy current and the maximum load generated by halo current (occurring in two different time steps) are studied in two separated analyses. These were carried out considering the entire ST40 model with high degree of detail, allowing to accurately approximate its real behavior and to extrapolate the stress and deformation conditions on all the device elements. Specifically, the completeness of the model has guaranteed to study the global and the local stress state generated on the IVC2, on its supports and on all the components that weigh on it. [ABSTRACT FROM AUTHOR]

• Electro-Magnetic and structural evaluation of the loads coming from a plasma disruption event on ST40 structures, with particular focus to new inner vacuum chamber. • Successful application of a recently developed procedure based on the use of MAXFEA code in combination with ANSYS APDL in the context of the advanced non-conventional low aspect ratio tokamak ST40. • Evaluation of the induced eddy currents and related force distributions on the tokamak structures. Tokamak Energy Ltd. is developing compact fusion power plants based on two promising technologies, Spherical Tokamaks (STs) and High Temperature Superconductors (HTS), with the aim to build a first demonstrative plant by the 2030′s. On its path to fusion power, Tokamak Energy is presently operating ST40, a new generation ST that is currently the highest field device of its kind. In the near future, an important ST40 upgrade is planned and foresees the manufacturing and the installation of a new vacuum chamber, called IVC2. This upgrade will allow the exploitation of ST40 to its maximum performances enabling Double Null (DN) diverted operations with up to 2 MA of plasma current and 3 T of toroidal field. IVC2 is currently in the final design stage. The necessity to analyse in detail the Electro-Magnetic (EM) behaviour of this component under the loads coming from plasma disruptions has recently emerged in order to verify the design or drive further modifications. In this context, a study to analyse the EM response of IVC2 during a plasma Vertical Displacement Event (VDE) has been carried out using the MAXFEA code in combination with ANSYS APDL, following a recent workflow development. The main output of this study is the evaluation of the transient EM force density in IVC2 and other components for subsequent mechanical assessments. The aim of this paper is to present the results of this analysis to show the successful application of this procedure in the context of ST40 project. [ABSTRACT FROM AUTHOR]

• First ideal MHD spectral analysis simulations performed on experimental ST40 equilibria. • Critical β T (β T above which no TAE modes are found) is shown to decrease with increased elongation, increased toroidal field (relative to a fixed plasma current) and a flatter current density profile. • Calculation of β T values that correspond to TAE free regimes for ST40 and future power plant scale devices. Spherical Tokamaks (STs) with a high normalised plasma pressure parameter β T are promising alternative pathways for net gain magnetic fusion reactors. Toroidal Alfvén eigenmodes (TAEs) excited via wave-particle resonances by fusion-born alpha-particles are of major concern for burning deuterium-tritium (D-T) plasmas in magnetic fusion as AEs cause a radial re-distribution of alpha-particles affecting their plasma heating efficiency and causing alpha-losses to the first wall. Tokamak plasmas with high pressure gradients were found to suppress toroidally induced Alfvén eigenmodes (TAEs) in ideal incompressible MHD and the high plasma β T attained by STs is expected to facilitate access to these TAE-free regimes. However, the low magnetic shear inherent to STs can lead to the formation of multiple AEs, which may increase transport due to the larger resonance area of the alpha-particle phase space. A suite of MHD codes HELENA, MISHKA and CS_MISH are used to investigate the discrete AE spectrum in high-pressure STs in the current paper. TAEs for an experimental ST40 magnetic equilibrium are computed and through varying β T and the current density profile the suppression of TAEs is investigated. The critical β T (above which no TAE modes are found) is shown to decrease with increased ellipticity, increased toroidal field (relative to a fixed plasma current) and a flatter current density profile. Despite the increase in the number of core-localised TAEs at low magnetic shear, the modes appear more sensitive to increases in β T and disappear at lower thresholds. [ABSTRACT FROM AUTHOR]

The development of rational methods to design ‘continuous’ sequence mimetics of discontinuous regions of protein sequence has, to now, been only marginally successful. This has been largely due to the difficulty of constraining the recognition elements of a mimetic structure to the relative conformational and spatial orientations present in the parent molecule. Using peptide mapping to determine ‘active’ antigen recognition residues, molecular modeling, and a molecular dynamics trajectory analysis, we have developed a peptide mimic of an anti-CD4 antibody, containing antigen contact residues from multiple CDRs. The design described is a 27-residue peptide formed by juxtaposition of residues from 5 CDR regions. It displays an affinity for the antigen (CD4) of 0.9 nM, compared to 2 nM for the parent antibody ST40. Nevertheless, the mimetic shows low biological activity in an anti-retroviral assay. [Copyright &y& Elsevier]