{"title":"Effects of guard and boom on needle Langmuir probes studied with particle-in-cell simulations","authors":"S.M. Brask, S. Marholm, W.J. Miloch, R. Marchand","doi":"10.1017/s0022377823001411","DOIUrl":"https://doi.org/10.1017/s0022377823001411","url":null,"abstract":"We investigate the effects of different guard geometries on the currents to needle-type Langmuir probes. The results are based on particle-in-cell numerical simulations. We show that if the guard length is less than 6–8 Debye lengths there can be a significant effect on the currents to the probe. A guard radius should not be larger than the Debye length, otherwise it can also significantly affect the currents. However, since guard radii are often close to the probe radius, the second condition is usually satisfied.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"29 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139921388","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":"Emission of terahertz pulses from near-critical plasma slab under action of p-polarized laser radiation","authors":"A.A. Frolov","doi":"10.1017/s0022377824000011","DOIUrl":"https://doi.org/10.1017/s0022377824000011","url":null,"abstract":"The theory of the terahertz (THz) waves emission from a near-critical plasma slab under the action of the focused <jats:italic>p</jats:italic>-polarized laser pulse is developed. The spectral, angular and energy characteristics of the THz signal are studied as functions of the focusing degree and the incidence angle of laser radiation, as well as the density and thickness of the plasma slab. It is shown that the extremely strong increase in the energy of the THz signal (up to millijoule level) and conversion rate (up to 10 %) occurs at the almost normal incidence of the ultra-short, tightly focused <jats:italic>p</jats:italic>-polarized laser pulse on the thin plasma slab with the near-critical density and rare electron collisions.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"63 1 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139921195","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}
C. Chen, K. M. Rabadanov, N. A. Ashurbekov, C. Yuan, A. M. Shakhrudinov
{"title":"Transverse magnetic field effects on the high-voltage pulsed discharge plasma in helium","authors":"C. Chen, K. M. Rabadanov, N. A. Ashurbekov, C. Yuan, A. M. Shakhrudinov","doi":"10.1017/s0022377824000138","DOIUrl":"https://doi.org/10.1017/s0022377824000138","url":null,"abstract":"This study investigates the effect of a transverse magnetic field on high-voltage pulsed discharge in helium at a pressure of 30 Torr. A simple two-dimensional fluid model that describes the high-voltage pulsed discharge in helium in a transverse weak magnetic field (<jats:italic>B</jats:italic> = 0.4 T) is presented, which uses an empirical relation to account for the magnetic field. The results of using the empirical relation for the effective field agree well with the experimental results. The dynamics of discharge development in the presence of the magnetic field is also investigated. The magnetic field does not significantly affect the gas-discharge development dynamics in helium at a pressure of 30 Torr.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"40 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139928179","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":"Trivelpiece–Gould modes and low-frequency electron–ion instability of non-neutral plasma","authors":"Yuriy N. Yeliseyev","doi":"10.1017/s002237782300137x","DOIUrl":"https://doi.org/10.1017/s002237782300137x","url":null,"abstract":"The frequency spectra of the Trivelpiece–Gould modes of a waveguide partially filled with non-neutral plasma are determined numerically by solving the dispersion equation. The modes having azimuthal number <jats:inline-formula> <jats:alternatives> <jats:tex-math>$m = 1$</jats:tex-math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S002237782300137X_inline1.png\" /> </jats:alternatives> </jats:inline-formula> are considered. The results are presented for the entire acceptable range of electron densities, magnetic field strengths, for different values of the charge neutralization coefficient. The Cherenkov resonance condition of an ion with a diocotron mode having a finite value of the longitudinal wave vector was studied. The characteristics of resonant low-frequency electron–ion instability caused by relative azimuth motion of electrons and ions in crossed fields and by the anisotropy of the distribution function of ions are discussed. Ions are created by ionization of residual gas in the plasma volume. Due to the anisotropy, instability occurs not only in the vicinity of the resonance, but also outside it. For typical values of plasma parameters in experiments, estimations of the frequency growth rate are given. A conclusion is drawn that this instability can be the cause of the low-frequency oscillations observed in linear devices with non-neutral plasma produced in an electron beam channel.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"7 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139761027","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":"Nonlinear Hall effect in the stationary a cylinder with a radial heat flux","authors":"G.S. Bisnovatyi-Kogan, M.V. Glushikhina","doi":"10.1017/s0022377824000102","DOIUrl":"https://doi.org/10.1017/s0022377824000102","url":null,"abstract":"A conducting cylinder with a uniform magnetic field along its axis and radial temperature gradient is considered at the stationary state. At large temperature gradients the azimuthal Hall electrical current creates an axial magnetic field whose strength may be comparable with the original one. It is shown that the magnetic field, generated by the azimuthal Hall current, leads to the decrease of a magnetic field originated by external sources, and this suppression increases with an increase of the electromotive force, connected with thermodiffusion. Obtained results can help to investigate the influence of the Hall current on the coupled magnetothermal evolution of magnetic and electric fields in neutron stars, white dwarfs and, possibly, in laboratory facilities.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"14 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139761251","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":"Calibrated heating rate measurements using electric-field-induced electron extraction in ultracold neutral plasmas","authors":"John M. Guthrie, Puchang Jiang, Jacob L. Roberts","doi":"10.1017/s0022377824000114","DOIUrl":"https://doi.org/10.1017/s0022377824000114","url":null,"abstract":"The heating rate of plasma electrons induced by external fields or other processes can be used as an experimental tool to measure fundamental plasma properties such as electrical conductivity or electron–ion collision rates. We have developed a technique that can measure electron heating rates in ultracold neutral plasmas (UNPs) with <jats:inline-formula> <jats:alternatives> <jats:tex-math>$sim 10,%$</jats:tex-math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0022377824000114_inline2.png\" /> </jats:alternatives> </jats:inline-formula> precision while simultaneously referencing the measurement to a calibrated amount of heating. This technique uses a sequence of applied electric fields in four sections: to control the ratio of electrons to ions in the UNP; to provide a time for the application of fields that cause electron heating and subsequent thermalization of the electrons after the application of those fields; to extract electrons from the UNP using a method sensitive to electron temperature that allows the measurement of electron heating; and to extract the remaining electrons to measure the total electron (and therefore ion) number. The primary signal used to measure the heating rate is the measurement of the number of electrons that escape in the third section of the experiment as a larger number of escaping electrons indicates a larger amount of heating. We illustrate the use of this technique by measuring electron heating caused by high-frequency radiofrequency (RF) fields. In addition to the main technique, several subtechniques to calibrate the electron temperature, electron density, amount of heating and applied RF field amplitude were developed as well.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"1 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139760853","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}
T. Van Doorsselaere, N. Magyar, M.V. Sieyra, M. Goossens
{"title":"The magnetohydrodynamic equations in terms of waveframe variables","authors":"T. Van Doorsselaere, N. Magyar, M.V. Sieyra, M. Goossens","doi":"10.1017/s0022377824000126","DOIUrl":"https://doi.org/10.1017/s0022377824000126","url":null,"abstract":"Generalising the Elsässer variables, we introduce the <jats:inline-formula> <jats:alternatives> <jats:tex-math>$Q$</jats:tex-math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0022377824000126_inline1.png\" /> </jats:alternatives> </jats:inline-formula>-variables. These are more flexible than the Elsässer variables, because they also allow us to track waves with phase speeds different than the Alfvén speed. We rewrite the magnetohydrodynamics (MHD) equations with these <jats:inline-formula> <jats:alternatives> <jats:tex-math>$Q$</jats:tex-math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0022377824000126_inline2.png\" /> </jats:alternatives> </jats:inline-formula>-variables. We consider also the linearised version of the resulting MHD equations in a uniform plasma, and recover the classical Alfvén waves, but also separate the fast and slow magnetosonic waves into upward- and downward-propagating waves. Moreover, we show that the <jats:inline-formula> <jats:alternatives> <jats:tex-math>$Q$</jats:tex-math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0022377824000126_inline3.png\" /> </jats:alternatives> </jats:inline-formula>-variables may also track the upward- and downward-propagating surface Alfvén waves in a non-uniform plasma, displaying the power of our generalisation. In the end, we lay the mathematical framework for driving solar wind models with a multitude of wave drivers.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"14 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139761026","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}
M. Cavenago, M. Romé, G. Maero, F. Cavaliere, M. Comunian, M. Maggiore, A. Ruzzon
{"title":"Ion transport and gas collision effects in a radio frequency quadrupole cooler: installation in the Eltrap solenoid and beam calculations","authors":"M. Cavenago, M. Romé, G. Maero, F. Cavaliere, M. Comunian, M. Maggiore, A. Ruzzon","doi":"10.1017/s0022377823001484","DOIUrl":"https://doi.org/10.1017/s0022377823001484","url":null,"abstract":"Radio frequency quadrupole coolers (RFQCs) are very suitable to cool ion beams with moderate energy spread, typically ions of exotic nuclear species (like <jats:inline-formula> <jats:alternatives> <jats:tex-math>$^{132}$</jats:tex-math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0022377823001484_inline1.png\" /> </jats:alternatives> </jats:inline-formula>Sn<jats:inline-formula> <jats:alternatives> <jats:tex-math>$^{1+}$</jats:tex-math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0022377823001484_inline2.png\" /> </jats:alternatives> </jats:inline-formula>) as in the Selective Production of Exotic Species project at the Laboratori Nazionali di Legnaro, whose ion source supplies 40 keV ions. Beam dynamics includes ion–gas collisions (with a balance of cooling and diffusion effects), acceleration and deceleration and radiofrequency confinement, which can be supplemented by static magnetic field effects. Insertion of a prototype RFQC in the solenoid of the Eltrap machine is also discussed here, with innovations in beam extraction and in modelling, now also based on stochastic equations. Practical consideration on gas pumping and voltage distribution are also included. Typical limits of RFQC are discussed, with special attention to the extracted beam root mean square emittance, which is shown to strongly depend not only on cooler parameters, but also on extraction optics.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"5 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139760851","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}
Mikhail S. Tolkachev, Anna A. Inzhevatkina, Anton V. Sudnikov, Ivan S. Chernoshtanov
{"title":"Electromagnetic oscillations and anomalous ion scattering in the helically symmetric multiple-mirror trap","authors":"Mikhail S. Tolkachev, Anna A. Inzhevatkina, Anton V. Sudnikov, Ivan S. Chernoshtanov","doi":"10.1017/s0022377823001496","DOIUrl":"https://doi.org/10.1017/s0022377823001496","url":null,"abstract":"The paper presents an investigation of the plasma fluctuation in the SMOLA helical mirror, which is suspected to be responsible for anomalous scattering. The helical mirror confinement is effective when the ion mean free path is equal to the helix pitch length. This condition can be satisfied in hot collisionless plasma only by anomalous scattering. The wave, which scatters the passing ions, is considered to receive energy from the trapped ions. The oscillations of the electric field in the helically symmetric plasma were observed in experiment. The oscillations have both regular highly correlated and chaotic components. The dependency of the regular component frequency on the Alfvén velocity is linear for <jats:inline-formula> <jats:alternatives> <jats:tex-math>$V_{rm A} < 2.8 times 10^6 text {m} text {s}^{-1}$</jats:tex-math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0022377823001496_inline2.png\" /> </jats:alternatives> </jats:inline-formula> and constant for higher values. It is shown experimentally that the condition for the wave to be in phase resonance with the trapped ions is satisfied in a specific region of the plasma column for the highly correlated component. The amplitude of the chaotic component (up to <jats:inline-formula> <jats:alternatives> <jats:tex-math>$3 text {V} text {cm}^{-1}$</jats:tex-math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0022377823001496_inline3.png\" /> </jats:alternatives> </jats:inline-formula>) is higher than the estimated electric field required for the ion scattering.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"16 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139760854","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":"Transformation of a plasma boundary curvature into electrical impulses moving along a plasma surface","authors":"O.M. Gradov","doi":"10.1017/s0022377824000084","DOIUrl":"https://doi.org/10.1017/s0022377824000084","url":null,"abstract":"The self-consistent propagation of electrical impulses and of the accompanying distortions of the electron surface in the framework of a cold plasma model with a sharp boundary has been described with help of a derived system of two equations. The method of ‘shallow water theory’ has been applied for the case of bounded plasma and deriving an equation with which to link the spatial and temporal structures and evolution of the boundary curvature and the surface charge. Under certain conditions, such perturbations can propagate along the boundary without changing their shape for a long distance. An approximate analytical solution has been found, and numerical calculations have been performed. Mutual connections between basic parameters of the considered perturbations (velocity components, electrostatic field, etc.) have been presented.","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"19 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2024-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139761029","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}