Measuring the beamlet divergence in NBI systems for fusion: A diagnostic comparison

Fusion Engineering and Design Elsevier 215 (2025) 114951

Authors:

Niek den Harder, Michael Barnes, Andreas Döring, Bernd Heinemann, Bruno Laterza, Isabella Mario, Antonio Pimazzoni, Carlo Poggi, Alessandro La Rosa, Emanuele Sartori, Beatrice Segalini, Gianluigi Serianni, Alastair Shepherd, Christian Wimmer, Dirk Wünderlich, Ursel Fantz

Prompt gravitational-wave mergers aided by gas in active galactic nuclei: the hydrodynamics of binary-single black hole scatterings

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 539:2 (2025) 1501-1515

Authors:

Connar Rowan, Henry Whitehead, Gaia Fabj, Pankaj Saini, Bence Kocsis, Martin Pessah, Johan Samsing

Beam focusing and consequences for Doppler backscattering measurements

Journal of Plasma Physics Cambridge University Press (CUP) 91:2 (2025) e60

Authors:

J Ruiz Ruiz, FI Parra, VH Hall-Chen, N Belrhali, C Giroud, JC Hillesheim, NA Lopez, JET contributors

Suppression of temperature-gradient-driven turbulence by sheared flows in fusion plasmas

Journal of Plasma Physics Cambridge University Press (CUP) 91:2 (2025) e58

Authors:

PG Ivanov, T Adkins, D Kennedy, M Giacomin, M Barnes, AA Schekochihin

Collisional whistler instability and electron temperature staircase in inhomogeneous plasma

Journal of Plasma Physics Cambridge University Press (CUP) 91:2 (2025) E45

Authors:

Na Lopez, Afa Bott, Aa Schekochihin

Abstract:

<jats:p>High-beta magnetised plasmas often exhibit anomalously structured temperature profiles, as seen from galaxy cluster observations and recent experiments. It is well known that when such plasmas are collisionless, temperature gradients along the magnetic field can excite whistler waves that efficiently scatter electrons to limit their heat transport. Only recently has it been shown that parallel temperature gradients can excite whistler waves also in collisional plasmas. Here, we develop a Wigner–Moyal theory for the collisional whistler instability starting from Braginskii-like fluid equations in a slab geometry. This formalism is necessary because, for a large region in parameter space, the fastest-growing whistler waves have wavelengths comparable to the background temperature gradients. We find additional damping terms in the expression for the instability growth rate involving inhomogeneous Nernst advection and resistivity. They (i) enable whistler waves to re-arrange the electron temperature profile via growth, propagation and subsequent dissipation, and (ii) allow non-constant temperature profiles to exist stably. For high-beta plasmas, the marginally stable solutions take the form of a temperature staircase along the magnetic field lines. The electron heat flux can also be suppressed by the Ettingshausen effect when the whistler intensity profile is sufficiently peaked and oriented opposite the background temperature gradient. This mechanism allows cold fronts without magnetic draping, might reduce parallel heat losses in inertial fusion experiments and generally demonstrates that whistler waves can regulate transport even in the collisional limit.</jats:p>