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High-power TCV scenario for conventional and alternative divertor studies
Authors:
K. Lee,
C. Theiler,
M. Carpita,
M. Zurita,
P. Sintre,
O. Février,
F. Pastore,
H. Reimerdes,
K. Verhaegh,
M. Winkel,
D. Brida,
B. Y. K. Brown,
M. J. H. Cornelissen,
R. Ducker,
G. Durr-Legoupil-Nicoud,
D. Hamm,
R. I. Morgan,
A. Perek,
O. Sauter,
E. Tonello,
Y. Wang,
the TCV Team,
the EUROfusion Tokamak Exploitation Team
Abstract:
Alternative divertor configurations (ADCs) must be evaluated under boundary plasma conditions approaching reactor-level values to be considered a reliable, physics-based solution for tokamak power exhaust. Most ADC experiments performed to date were at relatively low exhaust power. This work presents a high-power scenario on the TCV tokamak enabling the study of a wide variety of divertor magnetic…
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Alternative divertor configurations (ADCs) must be evaluated under boundary plasma conditions approaching reactor-level values to be considered a reliable, physics-based solution for tokamak power exhaust. Most ADC experiments performed to date were at relatively low exhaust power. This work presents a high-power scenario on the TCV tokamak enabling the study of a wide variety of divertor magnetic shapes under an expanded SOL and power exhaust parameter space. The scenario is characterized by high power levels of electron cyclotron resonance heating ($2.5\,\text{MW}$ fully absorbed in a $\sim1\,\text{m}^{3}$ plasma) at high plasma current (edge safety factor $q_{95}\approx 2.5$), and low upstream separatrix densities ($n_{e,\text{u}}\approx1\times10^{19}\,\text{m}^{-3}$, Greenwald fraction $f_{\text{G}}\approx 0.1$). Stationary parallel heat fluxes up to $100\,\text{MW m}^{-2}$ are measured at the divertor target, an order of magnitude above previous TCV power exhaust studies. The obtained SOL collisionality and Lengyel detachment scaling metric lie within range of values expected in future reactors (SPARC, ITER, ARC).
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Submitted 19 August, 2026;
originally announced August 2026.
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Detachment dynamics and disturbance rejection in the TCV X-Point Target divertor
Authors:
M. Winkel,
K. Verhaegh,
B. Kool,
K. Lee,
M. Carpita,
A. Perek,
R. Morgan,
G. Derks,
O. Février,
C. Theiler,
D. Brida,
M. van Berkel,
the TCV team,
the EUROfusion tokamak exploitation team
Abstract:
The X-Point Target divertor is an alternative divertor configuration with a secondary X-point in its divertor volume. In this work, we investigate the dynamic response and disturbance rejection capacity of the XPT configuration on the TCV tokamak, comparing it to a single null (SN) divertor. We employ a system identification approach using multi-sine perturbations to measure the dynamic response o…
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The X-Point Target divertor is an alternative divertor configuration with a secondary X-point in its divertor volume. In this work, we investigate the dynamic response and disturbance rejection capacity of the XPT configuration on the TCV tokamak, comparing it to a single null (SN) divertor. We employ a system identification approach using multi-sine perturbations to measure the dynamic response of the detached state in both Ohmic and auxiliary-heated L-mode scenarios upon D$_2$ fuelling, N$_2$ seeding and Electron Resonance Cyclotron Heating (ECRH) power modulations. We demonstrate an inherent disturbance rejection capacity of the XPT at its secondary X-point compared to a SN configuration for all perturbation scenarios. Upstream of its secondary X-point, the dynamic response of the detached state between the XPT and SN appears similar. The disturbance rejection capacity of the XPT could be highly beneficial for passively buffering disturbances that cannot be effectively managed by power exhaust controllers. At the same time, it presents a challenge for monitoring the detached state close to the secondary x-point.
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Submitted 22 June, 2026;
originally announced June 2026.
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Exploring Exoplanets with Interferometry
Authors:
Sascha P. Quanz,
Bertrand Mennesson,
Charles Beichman,
Jonah T. Hansen,
Felix A. Dannert,
Andrea Fortier,
Michael Ireland,
Nicholas Beltsten,
Eleonora Alei,
Leonid Pogorelyuk,
William O. Balmer,
Denis Defrère,
Gautam Vasisht,
Malcolm Fridlund,
Romain Laugier,
Tiffany Kataria,
Eugene Serabyn,
Steve Ertel,
Hélène Rousseau,
Kevin Wagner,
Rhonda Morgan,
Gerard T. van Belle,
Gail H. Schaefer,
Jean-Philippe Berger,
Taro Matsuo
, et al. (5 additional authors not shown)
Abstract:
(Extract from the Executive Summary) Humanity stands at the threshold of answering one of its most profound questions: Does life exist beyond Earth? Ongoing and upcoming space missions, together with powerful ground-based instruments, have prepared the way for a transformational next step - the detailed characterization of Earth analogs orbiting Sun-like and other stars and the search for atmosphe…
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(Extract from the Executive Summary) Humanity stands at the threshold of answering one of its most profound questions: Does life exist beyond Earth? Ongoing and upcoming space missions, together with powerful ground-based instruments, have prepared the way for a transformational next step - the detailed characterization of Earth analogs orbiting Sun-like and other stars and the search for atmospheric biosignatures that may indicate life. Within this context, the European Space Agency's Voyage 2050 process has identified the direct detection of thermal emission from temperate terrestrial exoplanets in the mid-infrared (mid-IR) as a top scientific priority. The Large Interferometer For Exoplanets (LIFE) - a space-based, mid-IR nulling interferometer - is designed to meet this goal. LIFE will be capable of detecting climate-relevant gases such as CO$_2$ and H$_2$O, identifying classical biosignatures like O$_3$ and CH$_4$, and probing additional, non-classical biosignatures. It will also provide key data for determining planetary radius, albedo, and temperature, which are essential for assessing habitability. In parallel, the U.S. National Academy has recommended a complementary mission now called the Habitable Worlds Observatory (HWO) - a ~6-meter space telescope equipped with advanced coronagraphs to suppress starlight by a factor of ~10$^{10}$ across the visible and possibly into the near-infrared and near-ultraviolet. Together, LIFE and HWO offer synergistic capabilities, enabling a comprehensive and robust assessment of the prevalence of life-bearing exoplanets in our galactic neighbourhood - a first in human history. By uniting an international and interdisciplinary community of scientists and engineers, LIFE offers a credible pathway toward the direct detection and characterization of potentially habitable - and even inhabited - worlds.
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Submitted 8 June, 2026;
originally announced June 2026.
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On the origins of Lagrangian hydrodynamic methods
Authors:
N. R. Morgan,
B. J. Archer
Abstract:
The intent of this paper is to discuss the history and origins of Lagrangian hydrodynamic methods for simulating shock driven flows. The majority of the pioneering research occurred within the Manhattan Project. A range of Lagrangian hydrodynamic schemes were created between 1943 and 1948 by John von Neumann, Rudolf Peierls, Tony Skyrme, and Robert Richtmyer. These schemes varied significantly fro…
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The intent of this paper is to discuss the history and origins of Lagrangian hydrodynamic methods for simulating shock driven flows. The majority of the pioneering research occurred within the Manhattan Project. A range of Lagrangian hydrodynamic schemes were created between 1943 and 1948 by John von Neumann, Rudolf Peierls, Tony Skyrme, and Robert Richtmyer. These schemes varied significantly from each other; however, they all used a staggered-grid and finite difference approximations of the derivatives in the governing equations, where the first scheme was by von Neumann. These ground-breaking schemes were principally published in Los Alamos laboratory reports that were eventually declassified many decades after authorship, which motivates us to document the work and describe the accompanying history in a paper that is accessible to the broader scientific community. Furthermore, we seek to correct historical omissions on the pivotal contributions made by Peierls and Skyrme to creating robust Lagrangian hydrodynamic methods for simulating shock driven flows. Understanding the history of Lagrangian hydrodynamic methods can help explain the origins of many modern schemes and may inspire the pursuit of new schemes.
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Submitted 10 March, 2021;
originally announced March 2021.
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A discontinuous Galerkin method based on a hierarchical orthogonal basis for Lagrangian hydrodynamics on curvilinear grids
Authors:
Xiaodong Liu,
Nathaniel R. Morgan,
Evan J. Lieberman,
Donald E. Burton
Abstract:
We present a new high-order accurate Lagrangian discontinuous Galerkin (DG) hydrodynamic method to simulate material dynamics (for e.g., gasses, fluids, and solids) with up to fourth-order accuracy on cubic meshes. The variables, such as specific volume, velocity, specific total energy, and deformation gradient fields within a cell, are represented with a polynomial constructed from a novel hierar…
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We present a new high-order accurate Lagrangian discontinuous Galerkin (DG) hydrodynamic method to simulate material dynamics (for e.g., gasses, fluids, and solids) with up to fourth-order accuracy on cubic meshes. The variables, such as specific volume, velocity, specific total energy, and deformation gradient fields within a cell, are represented with a polynomial constructed from a novel hierarchical orthogonal basis about the center of mass, which decouples the moments of the solution because the mass matrix is diagonal. The discontinuity in the polynomials at the cell boundary is addressed by solving a multi-directional Riemann problem at the vertices of the cell and a 1D Riemann problem at additional non-vertex quadrature points along the edges so that the surface integral is exact for the polynomial order. The uniqueness lies in that the vertices of the curvilinear grid work as the quadrature points for the surface integral of DG methods. To ensure robust mesh motion, the pressure for the Riemann problem accounts for the difference between the density variation over the cell and a density field from subcell mesh stabilization (SMS). The accuracy and robustness of the new high-order accurate Lagrangian DG hydrodynamic method is demonstrated by simulating a diverse suite of challenging test problems covering gas and solid dynamic problems on curved grids.
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Submitted 23 February, 2021;
originally announced March 2021.
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Morphological analysis of chiral rod clusters from a coarse-grained single-site chiral potential
Authors:
B. J. Sutherland,
S. W. Olesen,
H. Kusumaatmaja,
J. W. R. Morgan,
D. J. Wales
Abstract:
We present a coarse-grained single-site potential for simulating chiral interactions, with adjustable strength, handedness, and preferred twist angle. As an application, we perform basin-hopping global optimisation to predict the favoured geometries for clusters of chiral rods. The morphology phase diagram based upon these predictions has four distinct families, including previously reported struc…
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We present a coarse-grained single-site potential for simulating chiral interactions, with adjustable strength, handedness, and preferred twist angle. As an application, we perform basin-hopping global optimisation to predict the favoured geometries for clusters of chiral rods. The morphology phase diagram based upon these predictions has four distinct families, including previously reported structures for potentials that introduce chirality based on shape, such as membranes and helices. The transition between these two configurations reproduces some key features of experimental results for {\it{fd}} bacteriophage. The potential is computationally inexpensive, intuitive, and versatile; we expect it will be useful for large scale simulations of chiral molecules. For chiral particles confined in a cylindrical container we reproduce the behaviour observed for fusilli pasta in a jar. Hence this chiropole potential has the capability to provide insight into structures on both macroscopic and molecular length scales.
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Submitted 1 October, 2019;
originally announced October 2019.
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Symmetry-preserving WENO limiters
Authors:
Xiaodong Liu,
Nathaniel R. Morgan,
Donald E. Burton
Abstract:
Weighted essentially non-oscillatory (WENO) reconstruction schemes are presented that preserve cylindrical symmetry for radial flows on an equal-angle polar mesh. These new WENO schemes are used with a Lagrangian discontinuous Galerkin (DG) hydrodynamic method. The solution polynomials are reconstructed using the WENO schemes where the DG solution is the central stencil. A suite of challenging tes…
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Weighted essentially non-oscillatory (WENO) reconstruction schemes are presented that preserve cylindrical symmetry for radial flows on an equal-angle polar mesh. These new WENO schemes are used with a Lagrangian discontinuous Galerkin (DG) hydrodynamic method. The solution polynomials are reconstructed using the WENO schemes where the DG solution is the central stencil. A suite of challenging test problems are calculated to demonstrate the accuracy and robustness of the new WENO schemes.
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Submitted 20 August, 2019;
originally announced August 2019.
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Energy Landscapes for Digital Alchemy
Authors:
John W. R. Morgan,
Sharon C. Glotzer
Abstract:
We apply energy landscape methods to digital alchemy, defining a system in which the parameters of the potential are treated as degrees of freedom. Using geometrical optimisation, we locate minima and transition states on the landscape for small clusters. We show that it is easy to find the parameters that give the lowest energy minimum, and that the distribution of minima on the alchemical landsc…
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We apply energy landscape methods to digital alchemy, defining a system in which the parameters of the potential are treated as degrees of freedom. Using geometrical optimisation, we locate minima and transition states on the landscape for small clusters. We show that it is easy to find the parameters that give the lowest energy minimum, and that the distribution of minima on the alchemical landscape is concentrated in particular areas. We also conclude that the alchemical landscape is more frustrated, in terms of competition between low energy structures separated by high barriers. Transition states on the alchemical landscape are classified by whether they become minima or transition states when the potential parameters are fixed. Those that become minima have a significant alchemical component, while those that remain as transition states can be characterised mainly in terms of atomic displacements.
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Submitted 25 June, 2019;
originally announced June 2019.
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Disconnected Loop Subtraction Methods in Lattice QCD
Authors:
Suman Baral,
Travis Whyte,
Walter Wilcox,
Ronald B. Morgan
Abstract:
Lattice QCD calculations of disconnected quark loop operators are extremely computer time-consuming to evaluate. To compute these diagrams using lattice techniques, one generally uses stochastic noise methods. These employ a randomly generated set of noise vectors to project out physical signals. In order to strengthen the signal in these calculations, various noise subtraction techniques may be e…
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Lattice QCD calculations of disconnected quark loop operators are extremely computer time-consuming to evaluate. To compute these diagrams using lattice techniques, one generally uses stochastic noise methods. These employ a randomly generated set of noise vectors to project out physical signals. In order to strengthen the signal in these calculations, various noise subtraction techniques may be employed. In addition to the standard method of perturbative subtraction, one may also employ matrix deflation techniques using the GMRES-DR and MINRES-DR algorithms as well as polynomial subtraction techniques to reduce statistical uncertainty. Our matrix deflation methods play two roles: they both speed up the solution of the linear equations as well as decrease numerical noise. We show how to combine deflation with either perturbative and polynomial methods to produce extremely powerful noise suppression algorithms. We use a variety of lattices to study the effects. In order to set a benchmark, we first use the Wilson matrix in the quenched approximation. We see strong low eigenmode dominance at kappa critical ($κ_{crit}$) in the variance of the vector and scalar operators. We also use MILC dynamic lattices, where we observe deflation subtraction results consistent with the effectiveness seen in the quenched data.
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Submitted 16 March, 2019;
originally announced March 2019.
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Properties of Kinetic Transition Networks for Atomic Clusters and Glassy Solids
Authors:
John W R Morgan,
Dhagash Mehta,
David J Wales
Abstract:
A database of minima and transition states corresponds to a network where the minima represent nodes and the transition states correspond to edges between the pairs of minima they connect via steepest-descent paths. Here we construct networks for small clusters bound by the Morse potential for a selection of physically relevant parameters, in two and three dimensions. The properties of these unwei…
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A database of minima and transition states corresponds to a network where the minima represent nodes and the transition states correspond to edges between the pairs of minima they connect via steepest-descent paths. Here we construct networks for small clusters bound by the Morse potential for a selection of physically relevant parameters, in two and three dimensions. The properties of these unweighted and undirected networks are analysed to examine two features: whether they are small-world, where the shortest path between nodes involves only a small number or edges; and whether they are scale-free, having a degree distribution that follows a power law. Small-world character is present, but statistical tests show that a power law is not a good fit, so the networks are not scale-free. These results for clusters are compared with the corresponding properties for the molecular and atomic structural glass formers ortho-terphenyl and binary Lennard-Jones. These glassy systems do not show small-world properties, suggesting that such behaviour is linked to the structure-seeking landscapes of the Morse clusters.
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Submitted 6 September, 2017;
originally announced September 2017.
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Population trapping in bound states during IR-assisted ultra-fast photoionization of Ne$^+$
Authors:
H. W. van der Hart,
R. Morgan
Abstract:
We have investigated photoionization of Ne$^+$ in the combined field of a short infra-red laser pulse and a delayed ultra-short pulse of the infra-red laser's 23$^r$$^d$ harmonic. We observe an ionization yield compatible with a picture in which one electron gets excited into Rydberg states by the harmonic laser field and is subsequently removed by the infra-red laser field. Modulations are seen i…
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We have investigated photoionization of Ne$^+$ in the combined field of a short infra-red laser pulse and a delayed ultra-short pulse of the infra-red laser's 23$^r$$^d$ harmonic. We observe an ionization yield compatible with a picture in which one electron gets excited into Rydberg states by the harmonic laser field and is subsequently removed by the infra-red laser field. Modulations are seen in the ionization yield as a function of time delay. These modulations originate from the trapping of population in low members of the Rydberg series with different states being populated at different ranges of delay times. The calculations further demonstrate that single-threshold calculations cannot reproduce the Ne$^+$ photoionization yields obtained in multi-threshold calculations.
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Submitted 11 July, 2014;
originally announced July 2014.
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Deflated Iterative Methods for Linear Equations with Multiple Right-Hand Sides
Authors:
Ronald B. Morgan,
Walter Wilcox
Abstract:
A new approach is discussed for solving large nonsymmetric systems of linear equations with multiple right-hand sides. The first system is solved with a deflated GMRES method that generates eigenvector information at the same time that the linear equations are solved. Subsequent systems are solved by combining an iterative method with a projection over the previously determined eigenvectors. Res…
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A new approach is discussed for solving large nonsymmetric systems of linear equations with multiple right-hand sides. The first system is solved with a deflated GMRES method that generates eigenvector information at the same time that the linear equations are solved. Subsequent systems are solved by combining an iterative method with a projection over the previously determined eigenvectors. Restarted GMRES is considered for the iterative method as well as non-restarted methods such as BiCGSTAB. These methods offer an alternative to block methods, and they can also be combined with a block approach. An example is given showing significant improvement for a problem from quantum chromodynamics.
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Submitted 13 July, 2004; v1 submitted 20 May, 2004;
originally announced May 2004.
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Differential light scattering: probing the sonoluminescence collapse
Authors:
G. Vacca,
R. D. Morgan,
R. B. Laughlin
Abstract:
We have developed a light scattering technique based on differential measurement and polarization (differential light scattering, DLS) capable in principle of retrieving timing information with picosecond resolution without the need for fast electronics. DLS was applied to sonoluminescence, duplicating known results (sharp turnaround, self-similar collapse); the resolution was limited by intensi…
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We have developed a light scattering technique based on differential measurement and polarization (differential light scattering, DLS) capable in principle of retrieving timing information with picosecond resolution without the need for fast electronics. DLS was applied to sonoluminescence, duplicating known results (sharp turnaround, self-similar collapse); the resolution was limited by intensity noise to about 0.5 ns. Preliminary evidence indicates a smooth turnaround on a time scale of a few hundred picoseconds, and suggests the existence of subnanosecond features within a few nanoseconds of the turnaround.
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Submitted 9 December, 1999;
originally announced December 1999.