Matthieu Dagousset, Alexander Fikri, Peter Hosemann
et al.
Abstract Quantification of irradiation damage is a key challenge for fusion energy deployment. This study presents an irradiation damage modeling campaign using the Monte Carlo-based PHITS (Particle and Heavy Ion Transport code System) code to evaluate candidate plasma-facing materials under deuterium–deuterium (D–D) and deuterium–tritium (D–T) fusion conditions. Within a broader phased-approach to commercial reactor development, the analysis focuses on an assessment of a currently installed laser fusion test chamber driven by a low-power direct-drive central-ignition laser system. The objectives are to (1) compare a conventional dry-wall architecture against a wetted first wall architecture incorporating a 3 mm flowing lead–lithium (PbLi) layer and (2) to quantify activation product generation. Neutron spectra, spatial energy deposition, displacement-per-atom (DPA), and activation profiles were computed for Reduced Activation Ferritic-Martensitic steel (F82H), stainless steel 316 L, tungsten, and ODS FeCrAl using PHITS tallies. Results show that the PbLi layer absorbs over 30× more energy and reduces surface DPA in the underlying solid substrate by up to three orders of magnitude. Activation analysis indicates fewer gamma-emitting isotopes and tritium-dominated activity in the wetted configuration compared to the dry wall. These results confirm the irradiation-mitigation benefits of thin liquid–metal wetted walls and provide guidance for first-wall design in small-scale fusion test reactors.
Abstract This is a summary paper of the research activities presented in the magnetic fusion EXperiment Confinement (EX-C) session at the 29th International Atomic Energy Agency (IAEA) Fusion Energy Conference (FEC 2023), London, United Kingdom, 16–21 October 2023. This session covers a wide range of topics related to confinement and transport of magnetic fusion plasmas. The key aspects addressed in the presentations include: (i) scenario development, (ii) turbulent transport and L-H transition physics, (iii) isotope effects on confinement, (iv) impurity transport and impact of impurities on confinement, (v) influence of fueling and energetic particles on confinement, and (vi) improvements in experimental capabilities. Highlighted results presented in those manuscripts are summarized in this paper.
In ITER, to mitigate the deleterious effects of plasma disruptions, massive quantities of radiating impurities will be injected into the disrupting plasma by shattered pellet injectors (SPI) to pre-emptively radiate away the stored thermal and magnetic energy (Lehnen et al Proc. 27th IAEA Fusion Energy Conf. (FEC 2018) (Gandhinagar, India) EX/P7-12). However, asymmetries in the radiation pattern could result in intense photon flashes during the thermal quench that could locally damage or erode the stainless steel plasma-facing surface of the diagnostic port plugs (Pitts et al 2015 J. Nucl. Mater. 463 748–75). Experiments have been undertaken at JET to assess the potential dependence of the radiated power asymmetry on plasma energy during SPI mitigated disruptions. Calculations of the toroidal asymmetry in the radiated power indicate that the toroidal peaking factor is largest near the SPI position and decreases with the plasma stored energy, which is a promising result in view of radiation heat loads during mitigated disruptions in ITER.
Abstract The paper provides a high level summary of the contributions given at the 29th International Atomic Energy Agency Fusion Energy Conference (FEC 2023) London, United Kingdom, 16–21 October 2023 (available at: https://iaea.org/events/fec2023) under the categories ‘Magnetic Fusion Experiments including validation’ (EX) and ‘Innovative & Alternative Concepts’ covering linear configuration, non-magnetic configurations, fusion-fission hybrids concepts. For the category EX, the summary is limited to three sub-categories Heating & Current Drive, Waves, Stability. The experimental results reported in this publication cover the period since the previous 28th FEC, which was a virtual event held from 10th to 15 May 2021.
The mini proceedings of the "Fourth International Workshop on the Extension Project for the J-PARC Hadron Experimental Facility (HEF-ex 2024) [https://kds.kek.jp/event/46965]" held at J-PARC, February 19-21, 2024, are presented. The workshop was devoted to discussing the physics case that connects both the present and the future Hadron Experimental Facility at J-PARC, covering a wide range of topics in flavor, hadron, and nuclear physics related to both experimental and theoretical activities being conducted at the facility.
Basic concepts and terminology of relativistic heavy-ion collision physics are introduced and illustrated by experimental results. Most plots are taken from a recent ALICE overview paper arxiv:2211.04384 [nucl-ex].
E. Spaulding, Alexis M. Feidler, Lio A. Cook
et al.
The intrinsically disordered RG/RGG repeat domain is found in several nucleolar and P-granule proteins, but how it influences their phase separation into biomolecular condensates is unclear. We survey all RG/RGG repeats in C. elegans and uncover nucleolar and P-granule-specific RG/RGG motifs. An uncharacterized protein, K07H8.10, contains the longest nucleolar-like RG/RGG domain in C. elegans. Domain and sequence similarity, as well as nucleolar localization, reveals K07H8.10 (NUCL-1) to be the homolog of Nucleolin, a protein conserved across animals, plants, and fungi, but previously thought to be absent in nematodes. Deleting the RG/RGG repeats within endogenous NUCL-1 and a second nucleolar protein, GARR-1 (GAR1), demonstrates these domains are dispensable for nucleolar accumulation. Instead, their RG/RGG repeats contribute to the phase separation of proteins into nucleolar sub-compartments. Despite this common RG/RGG repeat function, only removal of the GARR-1 RG/RGG domain affects worm fertility and development, decoupling precise sub-nucleolar structure from nucleolar function. Spaulding et al. survey RG/RGG repeats in C. elegans and identify the homologs of Nucleolin (NUCL-1) and GAR1 (GARR-1). RG/RGG repeats are dispensable for nucleolar accumulation but critical for sub-nucleolar phase separation.
This release includes data and information necessary to perform independent analyses of the COHERENT result presented in Akimov et al., arXiv:1708.01294 [nucl-ex]. Data is shared in a binned, text-based format, including both "signal" and "background" regions, so that counts and associated uncertainties can be quantitatively calculated for the purpose of separate analyses. This document describes the included information and its format, offering some guidance on use of the data. Accompanying code examples show basic interaction with the data using Python.
Release of COHERENT collaboration data from the first detection of coherent elastic neutrino-nucleus scattering (CEvNS) on argon. This release corresponds with the results of "Analysis A" published in Akimov et al., arXiv:2003.10630 [nucl-ex]. Data is shared in a binned, text-based format representing both "signal" and "backgrounds" along with associated uncertainties such that the included data can be used to perform independent analyses. This document describes the contents of the data release as well as guidance on the use of the data. Included example code in C++ (ROOT) and Python show one possible use of the included data.
A phenomenological extraction of pressure within the proton has recently been performed using JLab CLAS data (arXiv:2104.02031 [nucl-ex]). The extraction used a 3-dimensional Breit frame description in which the initial and final proton states have different momenta. Instead, we obtain the two-dimensional transverse light front pressure densities that incorporate relativistic effects arising from the boosts that cause the initial and final states to differ. The mechanical radius is then determined to be $0.518~ \pm 0.062_{\mathrm{fit}} \pm 0.126_{\mathrm{sys}}~\mathrm{fm}$, which is smaller than the electric charge radius and larger than the light front momentum radius. The forces within the proton are shown to be predominantly repulsive at distances less than $0.43~\pm 0.12~\mathrm{fm}$ from the center, and predominantly attractive further out.
Aniruddha Dey, D. C. Biswas, A. Chakraborty
et al.
A detailed investigation on the relative isotopic distributions has been carried out for the first time in case of even-even correlated fission fragments for the $^{235}$U($n_{th}$,$f$) fission reaction. High-statistics data were obtained in a prompt $γ$ ray spectroscopy measurement during the EXILL campaign at ILL, Grenoble, France. The extensive off-line analysis of the coincidence data have been carried out using four different coincidence methods. Combining the results from 2-dimensional $γ-γ$ and 3-dimensional $γ-γ-γ$ coincidence analysis, a comprehensive picture of the relative isotopic yield distributions of the even-even neutron-rich fission fragments has emerged. The experimentally observed results have been substantiated by the theoretical calculations based on a novel approach of isospin conservation, and a reasonable agreement has been obtained. The calculations following the semi-empirical GEF model have also been carried out. The results from the GEF model calculations are found to be in fair agreement with the experimental results.
In this note we discuss subtleties associated with the efficiency corrections for measurements of off-diagonal cumulants and factorial moments for a situation when one deals with overlapping sets of particles, such as correlations between numbers of protons and positively charged particles. In particular, we discuss the situation commonly encountered in heavy-ion experiments, where first all charges are reconstructed and then protons are selected from these charges by an additional particle identification procedure. We present the efficiency correction formulas for the case when the detection efficiencies follow a binomial distribution.
Ground state properties of carbon isotopes, including root-mean-square radii, neutron separation energies, single particle spectra, and shapes are systematically studied with the deformed relativistic Hartree-Bogoliubov theory in continuum. The calculations with the effective interaction PK1 reproduce the available data reasonably well. The shell evolution in this isotopic chain is investigated by examining the single particle spectra. The inversion of neutron orbitals $ν2s_{1/2}$ and $ν1d_{5/2}$ compared with the order of neutron orbitals in stable nuclei is revealed in $^{15-20,22}\mathrm{C}$ when these nuclei are constrained to spherical shape. Neutron halos in $^{15,19,22}$C are studied in detail and their halo structures are mainly caused by the inversion of ($ν2s_{1/2},ν1d_{5/2}$) and deformation effects. In particular, $^{15}$C and $^{22}$C are deformed halo nuclei with shape decoupling effects in ground states.
Recently an improved quenching factor (QF) measurement for low-energy nuclear recoils in CsI[Na] has been reported in arXiv:1907.04828 [nucl-ex]. The new energy-dependent QF is characterized by a reduced systematic uncertainty and leads to a better agreement between the experimental COHERENT data and the Standard Model (SM) expectation. In this work we report updated constraints on parameters that describe the process of coherent elastic neutrino-nucleus scattering within and beyond the SM and we also present how the new QF affects their interpretation.