Journal of Plasma Physics最新文献

{"title":"A simple model for internal transport barrier induced by fishbone in tokamak plasmas","authors":"Zhaoyang Liu, Guoyong Fu","doi":"10.1017/s0022377823001344","DOIUrl":"https://doi.org/10.1017/s0022377823001344","url":null,"abstract":"<p>Fishbone bursts have been observed to strongly correlate to internal transport barrier (ITB) formation in a number of tokamak devices. A simple model incorporating the fishbone dynamics and ion pressure gradient evolution is proposed in order to investigate the key physics parameters assisting the triggering of ITB. The time evolution of fishbone is described by the well-known predator–prey model. For each burst cycle, the energetic particles (EPs) resonantly interact with fishbone and are radially expelled from inner region leading to a radial current. A compensating bulk plasma return current and, hence, poloidal flow can be induced if the fishbone cycle frequency is greater than the poloidal flow damping rate. When the shear of the poloidal flow exceeds a critical value, the turbulent fluctuations are suppressed and the bulk ion pressure gradient transits to the high-confinement state. It is shown that this process is only sensitive to the deposition rate of the trapped EPs within the <span><span><span data-mathjax-type=\"texmath\"><span>$q=1$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20231227145526428-0286:S0022377823001344:S0022377823001344_inline1.png\"/></span></span> surface, but not sensitive to other parameters. A quantitative formula for the shearing rate of poloidal flow induced by fishbone bursts is derived and verified numerically.</p>","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"65 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139053363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intermittency of density fluctuations and zonal-flow generation in MAST edge plasmas","authors":"A. Sladkomedova, I. Cziegler, A.R. Field, A.A. Schekochihin, D. Dunai, P.G. Ivanov, the MAST-U Team and the EUROfusion MST1 Team","doi":"10.1017/s0022377823001277","DOIUrl":"https://doi.org/10.1017/s0022377823001277","url":null,"abstract":"<p>The properties of the edge ion-scale turbulence are studied using the beam emission spectroscopy (BES) diagnostic on MAST. Evidence of the formation of large-scale high-amplitude coherent structures, filamentary density blobs and holes, 2–4 cm inside the plasma separatrix is presented. Measurements of radial velocity and skewness of the density fluctuations indicate that density holes propagate radially inwards, with the skewness profile peaking at 7–10 cm inside the separatrix. Poloidal velocities of the density fluctuations measured using cross-correlation time delay estimation (CCTDE) are found to exhibit an intermittent behaviour. Zonal-flow analysis reveals the presence of poloidally symmetric coherent oscillations – low-frequency (LF) zonal flows and geodesic acoustic modes (GAM). Shearing rates of the observed zonal flows are found to be comparable to the turbulence decorrelation rate. The observed bursts in density-fluctuation power are followed by quiescent periods with a transient increase in the power of sheared flows. Three-wave interactions between broadband turbulence and a GAM are illustrated using the autobispectral technique. It is shown that the zonal flows and the density-fluctuation field are nonlinearly coupled and LF zonal flows mediate the energy transfer from high- to low-frequency density fluctuations.</p>","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"8 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139053253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gyrokinetic moment-based simulations of the Dimits shift","authors":"A.C.D. Hoffmann, B.J. Frei, P. Ricci","doi":"10.1017/s0022377823001320","DOIUrl":"https://doi.org/10.1017/s0022377823001320","url":null,"abstract":"We present a convergence study of the gyromoment (GM) approach, which is based on projecting the gyrokinetic distribution function onto a Hermite–Laguerre polynomial basis, focused on the cyclone base case (CBC) (Lin <jats:italic>et al.</jats:italic>, <jats:italic>Phys. Rev. Lett.</jats:italic>, vol. 83, no. 18, 1999, pp. 3645–3648) and Dimits shift (Dimits <jats:italic>et al.</jats:italic>, <jats:italic>Phys. Plasmas</jats:italic>, vol. 7, no. 3, 2000, pp. 969–983) as benchmarks. We report that the GM approach converges more rapidly in capturing the nonlinear dynamics of the CBC than the continuum GENE code (Jenko <jats:italic>et al.</jats:italic>, <jats:italic>Phys. Plasmas</jats:italic>, vol. 7, no. 5, 2000, pp. 1904–1910) when comparing the number of points representing the velocity space. Increasing the velocity dissipation improves the convergence properties of the GM approach, albeit yielding a slightly larger saturated heat flux. By varying the temperature equilibrium gradient, we show that the GM approach successfully reproduces the Dimits shift (Dimits <jats:italic>et al.</jats:italic>, <jats:italic>Phys. Plasmas</jats:italic>, vol. 7, no. 3, 2000, pp. 969–983) and effectively captures its width, which is in contrast to the gyrofluid framework. In the collisional regime, the convergence properties of the GM approach improve and a good agreement with previous global particle-in-cell results on transport is obtained (Lin <jats:italic>et al.</jats:italic>, <jats:italic>Phys. Rev. Lett.</jats:italic>, vol. 83, no. 18, 1999, pp. 3645–3648). Finally, we report that the choice of collision model has a minimal impact both on the ion temperature gradient growth rate and on the nonlinear saturated heat flux, at tokamak-relevant collisionality.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"29 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139053409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Loss and revival of coherence in the interaction between a positron beam and a photon field","authors":"F. Castelli, S. Cialdi, G. Costantini, R. Ferragut, M. Giammarchi, G. Gittini, M. Leone, G. Maero, S. Olivares, M. Romé, A. Simonetto, V. Toso","doi":"10.1017/s0022377823001319","DOIUrl":"https://doi.org/10.1017/s0022377823001319","url":null,"abstract":"We study the interaction between a positron beam in the single-particle regime in an interferometric configuration and a microwave electromagnetic field. We discuss the conditions under which quantum interference can be affected by the field and we outline its possible experimental study in the framework of QUantum interferometry and gravitation with Positrons and LASers (QUPLAS) experiment.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"91 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139053412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A buffer-gas trap for the NEPOMUC positron beam: optimization studies with electrons","authors":"A. Deller, C.W. Rogge, S. Desopo, E.V. Stenson, J.R. Danielson, M.R. Stoneking, C. Hugenschmidt, T. Sunn Pedersen, C.M. Surko","doi":"10.1017/s0022377823001241","DOIUrl":"https://doi.org/10.1017/s0022377823001241","url":null,"abstract":"<p>Buffer-gas traps (BGTs) use inelastic interactions with nitrogen molecules to capture positrons from a continuous beam. These devices are invaluable for high-resolution studies of matter–antimatter interactions, antihydrogen research and positronium laser spectroscopy. We present a new project with the goal of producing a non-neutral plasma containing <span><span><span data-mathjax-type=\"texmath\"><span>${sim }10^8$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20231220092024360-0938:S0022377823001241:S0022377823001241_inline1.png\"/></span></span> low-energy positrons by installing a BGT on the NEPOMUC (NEutron induced POsitron source MUniCh) high-intensity positron beam. Details of the BGT are outlined and results are presented from experiments in which an electron beam, with a similar intensity and energy spread to the remoderated NEPOMUC beam, was used to create pulses of non-neutral electron plasma. The device is a vital component of the APEX (A Positron Electron eXperiment) project, which aims to create a low-temperature electron–positron pair plasma.</p>","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"70 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138826081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quadruple Langmuir probe characterization of different fuel gases in a plasma deflagration accelerator","authors":"Aduragbemi A.T. Jibodu, Arnaud M. Ballande, Mark A. Cappelli","doi":"10.1017/s0022377823001381","DOIUrl":"https://doi.org/10.1017/s0022377823001381","url":null,"abstract":"<p>Astrophysical flows may be studied by reproducing similar conditions using a coaxial plasma accelerator operating in the deflagration regime (or plasma deflagration accelerator). This allows for the recreation and investigation of dynamics present in complex highly coupled plasma systems at the laboratory scale. We report on measurements of the plasma density, temperature, plasma potential and velocity found using a quadruple Langmuir probe (QLP) on such a deflagration accelerator in the form of the Stanford Coaxial High ENerGy (CHENG) device operating with multiple gases – specifically argon, nitrogen and hydrogen. Experiments show a general decrease in bulk plasma velocity with gas atomic mass from upwards of <span><span><span data-mathjax-type=\"texmath\"><span>$120 {rm km} {rm s}^{-1}$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20231219053848574-0922:S0022377823001381:S0022377823001381_inline1.png\"/></span></span> with hydrogen to less than <span><span><span data-mathjax-type=\"texmath\"><span>$30 {rm km} {rm s}^{-1}$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20231219053848574-0922:S0022377823001381:S0022377823001381_inline2.png\"/></span></span> with argon. There was an accompanying increase in peak plasma density with increasing atomic mass from <span><span><span data-mathjax-type=\"texmath\"><span>${sim }3times 10^{20} {rm m}^{-3}$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20231219053848574-0922:S0022377823001381:S0022377823001381_inline3.png\"/></span></span> with hydrogen to <span><span><span data-mathjax-type=\"texmath\"><span>${sim }1.5 times 10^{21} {rm m}^{-3}$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20231219053848574-0922:S0022377823001381:S0022377823001381_inline4.png\"/></span></span> with argon. It was found that the momentum flux and internal energy density also generally increase with atomic mass while the particle flux is constant between shots. Further investigation is needed to understand these correlations and the underlying physics. Lastly, comparisons with scaling laws show that while the CHENG device may be operated in such a way as to simulate the effects of bulk solar wind movement, it may not properly capture the thermal effects.</p>","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"1 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138821844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Helicity of the magnetic axes of quasi-isodynamic stellarators","authors":"Katia Camacho Mata, Gabriel G. Plunk","doi":"10.1017/s0022377823001204","DOIUrl":"https://doi.org/10.1017/s0022377823001204","url":null,"abstract":"<p>In this study, we explore the influence of the helicity of the magnetic axis – defined as the self-linking number of the curve – on the quality of quasi-isodynamic stellarator-symmetric configurations constructed using the near-axis expansion method (Plunk <span>et al.</span>, <span>J. Plasma Phys.</span>, vol. 85, 2019, 905850602; Camacho Mata <span>et al.</span>, <span>J. Plasma Phys.</span>, vol. 88, 2022, 905880503). A class of magnetic axes previously unexplored within this formalism is identified when analysing the axis shape of the QIPC configuration (Subbotin <span>et al.</span>, <span>Nucl. Fusion</span>, vol. 46, 2006, p. 921): the case of half-helicity (per field period). We show that these shapes are compatible with the near-axis formalism and how they can be used to construct near-axis stellarators with up to five field periods, <span><span><span data-mathjax-type=\"texmath\"><span>$defiotaslash{{require{HTML} style{display: inline-block; transform: rotate(-13deg)}{iota}}kern-7pt{require{HTML} style{display: inline-block; transform: rotate(-25deg)}{-}}}{epsilon _{mathrm {eff}}} approx 1.3,%$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20231215155329581-0753:S0022377823001204:S0022377823001204_inline1.png\"/></span></span>, and similar rotational transform to existing conventionally optimized designs, without the need of a plasma boundary optimization.</p>","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"12 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138716817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Slow positron production and storage for the ASACUSA-Cusp experiment","authors":"D.J. Murtagh, C. Amsler, H. Breuker, M. Bumbar, S. Chesnevskaya, G. Costantini, R. Ferragut, M. Giammarchi, A. Gligorova, G. Gosta, H. Higaki, E.D. Hunter, C. Killian, V. Kraxberger, N. Kuroda, A. Lanz, M. Leali, G. Maero, C. Malbrunot, V. Mascagna, Y. Matsuda, V. Mäckel, S. Migliorati, A. Nanda, L. Nowak, F. Parnefjord Gustafsson, S. Rheinfrank, M. Romé, M.C. Simon, M. Tajima, V. Toso, S. Ulmer, L. Venturelli, A. Weiser, E. Widmann, T. Wolz, Y. Yamazaki, J. Zmeskal","doi":"10.1017/s0022377823001034","DOIUrl":"https://doi.org/10.1017/s0022377823001034","url":null,"abstract":"<p>The ASACUSA (atomic spectroscopy and collisions using slow antiprotons) Cusp experiment requires the production of dense positron plasmas with a high repetition rate to produce a beam of antihydrogen. In this work, details of the positron production apparatus used for the first observation of the antihydrogen beam, and subsequent measurements, are described in detail. This apparatus replaced the previous compact trap design resulting in an improvement in the positron accumulation rate by a factor of <span><span><span data-mathjax-type=\"texmath\"><span>$52pm 3$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20231215104706423-0809:S0022377823001034:S0022377823001034_inline4.png\"/></span></span>.</p>","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"33 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138716691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deciphering the physical basis of the intermediate-scale instability","authors":"Mohamad Shalaby, Timon Thomas, Christoph Pfrommer, Rouven Lemmerz, Virginia Bresci","doi":"10.1017/s0022377823001289","DOIUrl":"https://doi.org/10.1017/s0022377823001289","url":null,"abstract":"<p>We study the underlying physics of cosmic ray (CR)-driven instabilities that play a crucial role for CR transport across a wide range of scales, from interstellar to galaxy cluster environments. By examining the linear dispersion relation of CR-driven instabilities in a magnetised electron–ion background plasma, we establish that both the intermediate and gyroscale instabilities have a resonant origin, and show that these resonances can be understood via a simple graphical interpretation. These instabilities destabilise wave modes parallel to the large-scale background magnetic field at significantly distinct scales and with very different phase speeds. Furthermore, we show that approximating the electron–ion background plasma with either magnetohydrodynamics (MHD) or Hall-MHD fails to capture the fastest-growing instability in the linear regime, namely the intermediate-scale instability. This finding highlights the importance of accurately characterising the background plasma for resolving the most unstable wave modes. Finally, we discuss the implications of the different phase speeds of unstable modes on particle–wave scattering. Further work is needed to investigate the relative importance of these two instabilities in the nonlinear, saturated regime and to develop a physical understanding of the effective CR transport coefficients in large-scale CR hydrodynamics theories.</p>","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"97 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138572080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The nonlinear evolution of whistler-mode chorus: modulation instability as the source of tones","authors":"Daniel J. Ratliff, Oliver Allanson","doi":"10.1017/s0022377823001265","DOIUrl":"https://doi.org/10.1017/s0022377823001265","url":null,"abstract":"<p>We review the modulation stability of parallel-propagating/field-aligned whistler-mode chorus (WMC) waves propagating in a warm plasma from a formal perspective with a focus on wave–particle interactions via ponderomotive forces. The modulation instability criteria are characterised by the group velocity dispersion, <span><span><span data-mathjax-type=\"texmath\"><span>$d c_g/dk$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20231209135147911-0331:S0022377823001265:S0022377823001265_inline1.png\"/></span></span>, for whistler-mode waves and a condition on the ratio between the group velocity <span><span><span data-mathjax-type=\"texmath\"><span>$c_g$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20231209135147911-0331:S0022377823001265:S0022377823001265_inline2.png\"/></span></span> and the electron sound speed <span><span><span data-mathjax-type=\"texmath\"><span>$c_{s,e}$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20231209135147911-0331:S0022377823001265:S0022377823001265_inline3.png\"/></span></span>. We also demonstrate that in order to investigate the spatiotemporal evolution of the envelope and the formation of packets (according to this mechanism), one necessarily needs to account for the motion of ions within the system, leading to an ionic influence on the modulation instability threshold determined by the ion fraction of the plasma. Finally, we demonstrate that chirping may be captured when higher-order effects are included within the spatiotemporal evolution of the amplitude. This yields not only an explicit expression for the sweep rate but also identifies a possible origin for the power band gap that occurs at half the electron gyrofrequency. Numerical validation demonstrates that the interaction between wave packets is a source for the emergence of tones observed within mission data, and such interactions may be a major source of the electron energisation which WMC are responsible for.</p>","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"1 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138574954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}