arXiv - PHYS - Plasma Physics最新文献

{"title":"On Extended d-D Kappa Distribution","authors":"Arak M. Mathai, Hans J. Haubold","doi":"arxiv-2407.21532","DOIUrl":"https://doi.org/arxiv-2407.21532","url":null,"abstract":"Thermal Doppler broadening of spectral profiles for particle populations in\u0000the absence or presence of potential fields are described by kappa\u0000distributions. The kappa distribution provides a replacement for the\u0000Maxwell-Boltzmann distribution which can be considered as a generalization for\u0000describing systems characterized by local correlations among their particles as\u0000found in space and astrophysical plasmas. This paper presents all special cases\u0000of kappa distributions as members of a general pathway family of densities\u0000introduced by Mathai.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First Access to ELM-free Negative Triangularity at Low Aspect Ratio","authors":"A. O. Nelson, C. Vincent, H. Anand, J. Lovell, J. F. Parisi, H. S. Wilson, K. Imada, W. P. Wehner, M. Kochan, S. Blackmore, G. McArdle, S. Guizzo, L. Rondini, S. Freiberger, C. Paz-Soldan","doi":"arxiv-2408.00180","DOIUrl":"https://doi.org/arxiv-2408.00180","url":null,"abstract":"A plasma scenario with negative triangularity (NT) shaping is achieved on\u0000MAST-U for the first time. While edge localized modes (ELMs) are eventually\u0000suppressed as the triangularity is decreased below $delta$ < -0.06, an\u0000extended period of H-mode operation with Type-III ELMs is sustained at less\u0000negative $delta$ even through access to the second stability region for ideal\u0000ballooning modes is closed. This documents a qualitative difference from the\u0000ELM-free access conditions documented in NT scenarios on conventional aspect\u0000ratio machines. The electron temperature at the pedestal top drops across the\u0000transition to ELM-free operation, but a steady rise in core temperature as\u0000$delta$ is decreased allows for similar normalized beta in the ELM-free NT and\u0000H-mode positive triangularity shapes.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bayesian optimization of laser wakefield acceleration in the self-modulated regime (SM-LWFA) aiming to produce molybdenum-99 via photonuclear reactions","authors":"B. S. Nunes, S. P. Santos, R. P. Nunes, C. Bonţoiu, M. S. Alva-Sánchez, R. E. Samad, N. D. Vieira Jr., G. Xia, J. Resta-López, A. Bonatto","doi":"arxiv-2407.20087","DOIUrl":"https://doi.org/arxiv-2407.20087","url":null,"abstract":"While laser wakefield acceleration (LWFA) in the bubble regime demands\u0000ultra-short, high-peak-power laser pulses, operation in the self-modulated\u0000regime (SM-LWFA) works with more relaxed pulse conditions, albeit at the cost\u0000of lower beam quality. Modern laser systems can deliver pulses with durations\u0000of a few tens of femtoseconds and peak powers on the order of a few terawatts,\u0000at kHz repetition rates. These systems are well-suited for developing SM-LWFA\u0000applications where high average energy and charge are prioritized over beam\u0000quality. Such beams could be used to generate high-energy bremsstrahlung\u0000photons, capable of triggering photonuclear reactions to produce radioisotopes\u0000like molybdenum-99. This isotope decays into technetium-99m, the most widely\u0000used medical radioisotope, with over 30 million applications worldwide per\u0000year. This work explores the use of Bayesian optimization to maximize the\u0000energy and charge of electron beams accelerated via SM-LWFA. Particle-in-cell\u0000(PIC) simulations model a 5 TW, 15 fs-long Gaussian laser pulse, propagating\u0000through tailored hydrogen gas-density profiles. In these simulations, over\u0000multiple iterations, the algorithm optimizes a set of input parameters\u0000characterizing the gas-density profile and the laser focal position. Three\u0000distinct profiles, with total lengths ranging from 200 to 400 micrometers and\u0000combining ramps and plateaus, were investigated. Optimal configurations were\u0000found to produce electron beams with median energies ranging from 14 to 17 MeV\u0000and charges of 600 to 1300 pC, considering electrons with energies above 8 MeV.\u0000Preliminary estimates of the molybdenum-99 yields for the optimal beams were\u0000obtained by employing their phase spaces, retrieved from PIC simulations, as\u0000radiation source inputs in Monte Carlo simulations irradiating a combined\u0000tantalum and molybdenum target.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"89 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141873307","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Polarization state control for high peak power applications","authors":"E. M. Starodubtseva, I. N. Tsymbalov, D. A. Gorlova, K. A. Ivanov, A. B. Savel'ev","doi":"arxiv-2407.20113","DOIUrl":"https://doi.org/arxiv-2407.20113","url":null,"abstract":"Numerous applications in the extreme field science are possible with\u0000circularly polarized high peak power ultrashort pulses. Commonly used quarter\u0000wave plates are not applicable here, while multi-mirror schemes are very\u0000complicated. We showed that the simple PET film $approx$20 $mu$m thick can be\u0000used to control the polarization state of the high peak power beam and achieve\u0000ellipticity of $approx$0.8 with negligible nonlinear phase distortion. The\u0000film can withstand $10^3$ shots at intensity of $I = 3 cdot 10^{12}$ W/cm$^2$\u0000without visible damage. Thus, for a PW laser system and beam diameter of 20 cm\u0000the PET film can be used for quite a long time. We proved this experimentally\u0000using 1 TW femtosecond Ti:Sa laser measuring the angular distribution of the\u0000second harmonic from the plasma channel created in an undercritical gas plume.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"87 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Collisionless zonal-flow dynamics in quasisymmetric stellarators","authors":"Hongxuan Zhu, Z. Lin, A. Bhattacharjee","doi":"arxiv-2407.19592","DOIUrl":"https://doi.org/arxiv-2407.19592","url":null,"abstract":"The linear collisionless plasma response to a zonal density perturbation in\u0000quasisymmetric stellarators is studied, including the initial\u0000geodesic-acoustic-mode oscillations and the final Rosenbluth--Hinton residual\u0000flow. While the geodesic-acoustic-mode oscillations in quasiaxisymmetric\u0000configurations are similar to tokamaks, they become almost nonexistent in\u0000quasi-helically symmetric configurations when the effective safety factor is\u0000small. Compared with concentric circular tokamaks, the Rosenbluth--Hinton\u0000residual is also found to be multiplied by a geometric factor $mathcal{C}$\u0000that arises from the flux-surface averaged classical polarization. Using the\u0000near-axis-expansion framework, we derive an analytic expression for\u0000$mathcal{C}$, which varies significantly among different configurations. These\u0000analytic results are compared with numerical simulation results from the global\u0000gyrokinetic particle-in-cell code GTC, and good agreement in the\u0000Rosenbluth--Hinton residual level is achieved only when the quasisymmetry error\u0000is small enough. Since zonal flows can be important for regulating turbulent\u0000transport, these results suggest possible relation between the transport level\u0000and the stellarator geometric parameters via nonlinear interactions with zonal\u0000flows.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A study of an air-breathing electrodeless plasma thruster discharge","authors":"Jiewei Zhou, Francesco Taccogna, Pablo Fajardo, Eduardo Ahedo","doi":"arxiv-2407.19322","DOIUrl":"https://doi.org/arxiv-2407.19322","url":null,"abstract":"Plasma chemistry of main air components is implemented in a hybrid 2D\u0000axisymmetric simulation code to assess the air-breathing concept in an\u0000electrodeless plasma thruster. Relevant electron-heavy species collisions for\u0000diatomic molecules are included: rotational and vibrational excitation,\u0000dissociation and dissociative ionization. Plasma-wall interaction giving rise\u0000to associative recombination of atomic species into molecular species is\u0000included too. As reference, the plasma thruster is operated with Xe, at a power\u0000of 300W and a mass flow of 1mg/s. Simulations are run by injecting 1mg/s of\u0000N$_2$ and O independently for powers between 100 and 3000W. The performances\u0000and trends of plasma response for these propellants are similar to Xe, but\u0000displaced to powers between 1250 and 2000W. At optimum power, the thrust\u0000efficiency for N$_2$ and O surpasses that of Xe, due to the excess of\u0000re-ionization for Xe. Performances of 50/50 mixtures of N$_2$/O, which are a\u0000realistic composition in the ionosphere, are found to be linear combinations of\u0000the performances of each propellant. Performances using O$_2$, which could be\u0000generated from associative recombination of O at the intake, are very similar\u0000to those of the atomic oxygen.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"96 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cross-Calibration and First Vertical ECE Measurement of Electron Energy Distribution in the TCV Tokamak","authors":"A. Tema Biwole, L. Porte, A. Fasoli, L. Figini, J. Decker, M. Hoppe, J. Cazabonne, L. Votta, A. Simonetto, S. Coda, TCV Team","doi":"arxiv-2407.18780","DOIUrl":"https://doi.org/arxiv-2407.18780","url":null,"abstract":"This paper describes the first Vertical Electron Cyclotron Emission (V-ECE)\u0000measurement of non-thermal electron distributions in the textit{Tokamak `a\u0000Configuration Variable}, TCV. These measurements were conducted in runaway\u0000electron scenarios and in the presence of Electron Cyclotron Current Drive.\u0000Measured intensities of linearly polarised X- and O-mode radiation from fast\u0000electrons allow the analysis of the energy distribution. The measurements were\u0000made possible through the creation of an operational regime for the diagnostic\u0000that is free of thermal background radiation, in relaxed electron density\u0000operations. This operational regime notably enables the cross-calibration of\u0000the diagnostic system, relying on thermal plasma measurements and modeling with\u0000the ray-tracing code SPECE.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"70 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Use of current-potential patches to obtain fundamental improvements to the coils of magnetic fusion devices","authors":"Allen H Boozer","doi":"arxiv-2407.19123","DOIUrl":"https://doi.org/arxiv-2407.19123","url":null,"abstract":"A central issue in the design of any magnetic fusion device is the coils that\u0000produce the external magnetic fields. The freedom that remains unstudied in the\u0000design of coils is enormous. This freedom could be quickly studied\u0000computationally at low cost with high reliability. This paper explains how this\u0000could be done using the concept of current-potential patches that was developed\u0000in Todd Elder's thesis.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"74 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transmission characteristics of millimeter and sub-terahertz channels through spatially ripple plasma sheath layers","authors":"Wenbo Liu, Peian Li, Da Li, Daniel M. Mittleman, Jianjun Ma","doi":"arxiv-2407.18476","DOIUrl":"https://doi.org/arxiv-2407.18476","url":null,"abstract":"The propagation of millimeter wave (MMW) and sub-terahertz (THz) signals\u0000through plasma sheaths is a critical concern for maintaining communication with\u0000hypersonic vehicles, yet the impact of complex plasma structures on these\u0000high-frequency channels remains insufficiently understood. In this work, we aim\u0000to characterize the transmission properties of MMW and sub-THz waves through\u0000plasma sheaths with various density profiles and ripple structures, addressing\u0000the gap in knowledge regarding the effects of plasma inhomogeneities on signal\u0000propagation. We employ an approach combining Inductively Coupled Plasma (ICP)\u0000data with transfer matrix methods (TMM) to model propagation through both flat\u0000and rippled plasma layers. Our findings reveal that ripple structures in plasma\u0000sheaths significantly affect channel performance, with periodic ripples\u0000reducing cutoff frequency and introducing frequency-selective behavior, while\u0000random ripples cause more unpredictable transmission characteristics. Our\u0000results explore the impact of the arrangement of plasma density layers and the\u0000parameters of ripple structures (period and amplitude) on channel transmission,\u0000group velocity dispersion, and angular dependence of wave propagation. These\u0000results provide crucial insights for the design and optimization of\u0000communication systems for hypersonic vehicles, potentially enabling the\u0000development of adaptive technologies capable of maintaining reliable\u0000communication in complex plasma environments.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Turbulent transport regimes in the presence of an X-point magnetic configuration","authors":"Fabio Moretti, Nakia Carlevaro, Francesco Cianfrani, Giovanni Montani","doi":"arxiv-2407.18634","DOIUrl":"https://doi.org/arxiv-2407.18634","url":null,"abstract":"We analyze the transport properties of the two-dimensional electrostatic\u0000turbulence characterizing the edge of a Tokamak device from the study of test\u0000particles motion (passive fluid tracers) following the EXB drift. We perform\u0000statistical tests on the tracer population in order to assess both the\u0000magnitude and the main features of transport. The role of other physical\u0000properties, such as viscosity and inverse energy cascade in the spectrum, is\u0000also considered. We outline that large scale eddies are responsible for greater\u0000transport coefficients, while the presence of an X-point magnetic field reduces\u0000the mean free path of the particles, however generating a larger outliers\u0000population with respect to a Gaussian profile.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}