Characteristics of the electromagnetic wave propagation in magnetized plasma sheath and practical method for blackout mitigation

“Magnetic window”is considered as an effective method to solve the communication blackout issue.COMSOL software package based on the finite element method is utilized to simulate the propagation of right-handed circularly polarized wave in the magnetized plasma sheath.We assume a double Gaussian model of electron density and an exponential attenuation model of magnetic field.The propagation characteristics of right-handed circularly polarized wave are analyzed by the observation of the reflected,transmitted and loss coefficient.The numerical results show that the propagation of right-handed circularly polarized wave in the magnetized plasma sheath varies for different incident angles,collision frequencies,non-uniform magnetic fields and non-uniform plasma densities.We notice that reducing the wave frequency can meet the propagation conditions of whistle mode in the weak magnetized plasma sheath.And the transmittance of whistle mode is less affected by the variation of the electron density and the collision frequency.It can be used as a communication window.

Magnetic diagnostics layout design for CFETR plasma equilibrium reconstruction

Plasma equilibrium reconstruction provides essential information for tokamak operation and physical analysis.An extensive and reliable set of magnetic diagnostics is required to obtain accurate plasma equilibrium.This study designs and optimizes the magnetic diagnostics layout for the reconstruction of the equilibrium of the plasma according to the scientific objectives,engineering design parameters,and limitations of the Chinese Fusion Engineering Test Reactor(CFETR).Based on the CFETR discharge simulation,magnetic measurement data are employed to reconstruct consistent plasma equilibrium parameters,and magnetic diagnostics'number and position are optimized by truncated Singular value decomposition,verifying the redundancy reliability of the magnetic diagnostics layout design.This provides a design solution for the layout of the magnetic diagnostics system required to control the plasma equilibrium of CFETR,and the developed design and optimization method can provide effective support to design magnetic diagnostics systems for future magnetic confinement fusion devices.

Diagnosing ratio of electron density to collision frequency of plasma surrounding scaled model in a shock tube using low-frequency alternating magnetic field phase shift

A non-contact low-frequency(LF)method of diagnosing the plasma surrounding a scaled model in a shock tube is proposed.This method utilizes the phase shift occurring after the transmission of an LF alternating magnetic field through the plasma to directly measure the ratio of the plasma loop average electron density to collision frequency.An equivalent circuit model is used to analyze the relationship of the phase shift of the magnetic field component of LF electromagnetic waves with the plasma electron density and collision frequency.The applicable range of the LF method on a given plasma scale is analyzed.The upper diagnostic limit for the ratio of the electron density(unit:m^(-3))to collision frequency(unit:Hz)exceeds 1×10^(11),enabling an electron density to exceed 1×10^(20)m^(-3)and a collision frequency to be less than 1 GHz.In this work,the feasibility of using the LF phase shift to implement the plasma diagnosis is also assessed.Diagnosis experiments on shock tube equipment are conducted by using both the electrostatic probe method and LF method.By comparing the diagnostic results of the two methods,the inversion results are relatively consistent with each other,thereby preliminarily verifying the feasibility of the LF method.The ratio of the electron density to the collision frequency has a relatively uniform distribution during the plasma stabilization.The LF diagnostic path is a loop around the model,which is suitable for diagnosing the plasma that surrounds the model.Finally,the causes of diagnostic discrepancy between the two methods are analyzed.The proposed method provides a new avenue for diagnosing high-density enveloping plasma.

Effect of ion stress on properties of magnetized plasma sheath

In the plasma sheath, there is a significant gradient in ion velocity, resulting in strong stress on ions treated as a fluid. This aspect has often been neglected in previous sheath studies. This study is based on the Braginskii plasma transport theory and establishes a 1D3V sheath fluid model that takes into account the ion stress effect. Under the assumption that ions undergo both electric and diamagnetic drift in the presheath region, self-consistent boundary conditions,including the ion Bohm velocity, are derived based on the property of the Sagdeev pseudopotential.Furthermore, assuming that the electron velocity at the wall follows a truncated Maxwell distribution, the wall floating potential is calculated, leading to a more accurate sheath thickness estimation. The results show that ion stress significantly reduces the sheath thickness, enhances ion Bohm velocity, wall floating potential, and ion flux at the wall. It hinders the acceleration of ions within the sheath, leading to notable alterations in the particle density profiles within the sheath. Further research indicates that in ion stress, bulk viscous stress has the greatest impact on sheath properties.

Model of self-generated magnetic field generation from relativistic laser interaction with solid targets

Generation of self-generated annular magnetic fields at the rear side of a solid target driven by relativistic laser pulse is investigated by using theoretical analysis and particle-in-cell simulations.The spatial strength distribution of magnetic fields can be accurately predicted by calculating the net flow caused by the superposition of source flow and return flow of hot electrons.The theoretical model established shows good agreement with the simulation results,indicating that the magnetic-field strength scales positively to the temperature of hot electrons.This provides us a way to improve the magnetic-field generation by using a micro-structured plasma grating in front of the solid target.Compared with that for a common flat target,hot electrons can be effectively heated with the well-designed grating size,leading to a stronger magnetic field.The spatial distribution of magnetic fields can be modulated by optimizing the grating period and height as well as the incident angle of the laser pulse.

Investigation on the roles of equilibrium toroidal rotation during edge-localized mode mitigated by resonant magnetic perturbations

The effects of equilibrium toroidal rotation during edge-localized mode(ELM)mitigated by resonant magnetic perturbation(RMP)are studied with the experimental equilibria of the EAST tokamak based on the four-field model in the BOUT++code.As the two main parameters to determine the toroidal rotation profiles,the rotation shear and magnitudes were separately scanned to investigate their roles in the impact of RMPs on peeling-ballooning(P-B)modes.On one hand,the results show that strong toroidal rotation shear is favorable for the enhancement of the self-generated E×B shearing rate<ω_(E×B)>with RMPs,leading to significant ELM mitigation with RMP in the stronger toroidal rotation shear region.On the other hand,toroidal rotation magnitudes may affect ELM mitigation by changing the penetration of the RMPs,more precisely the resonant components.RMPs can lead to a reduction in the pedestal energy loss by enhancing the multimode coupling in the turbulence transport phase.The shielding effects on RMPs increase with the toroidal rotation magnitude,leading to the enhancement of the multimode coupling with RMPs to be significantly weakened.Hence,the reduction in pedestal energy loss by RMPs decreased with the rotation magnitude.In brief,the results show that toroidal rotation plays a dual role in ELM mitigation with RMP by changing the shielding effects of plasma by rotation magnitude and affecting<ω_(E×B)>by rotation shear.In the high toroidal rotation region,toroidal rotation shear is usually strong and hence plays a dominant role in the influence of RMP on P-B modes,whereas in the low rotation region,toroidal rotation shear is weak and has negligible impact on P-B modes,and the rotation magnitude plays a dominant role in the influence of RMPs on the P-B modes by changing the field penetration.Therefore,the dual role of toroidal rotation leads to stronger ELM mitigation with RMP,which may be achieved both in the low toroidal rotation region and the relatively high rotation region that has strong rotational shear.

Unconditionally stable Crank-Nicolson algorithm with enhanced absorption for rotationally symmetric multi-scale problems in anisotropic magnetized plasma

Large calculation error can be formed by directly employing the conventional Yee’s grid to curve surfaces.In order to alleviate such condition,unconditionally stable CrankNicolson Douglas-Gunn(CNDG)algorithm with is proposed for rotationally symmetric multi-scale problems in anisotropic magnetized plasma.Within the CNDG algorithm,an alternative scheme for the simulation of anisotropic plasma is proposed in body-of-revolution domains.Convolutional perfectly matched layer(CPML)formulation is proposed to efficiently solve the open region problems.Numerical example is carried out for the illustration of effectiveness including the efficiency,resources,and absorption.Through the results,it can be concluded that the proposed scheme shows considerable performance during the simulation.

Effect of Viscous Dissipation (Φ) on Temperature Distribution of Blood Plasma in Presence of a Magnetic Field

Applications of heat transfer show the variations in temperature of the body which is helpful for the purpose of thermal therapy in the treatment of tumor glands. This study considered theoretical approaches in analyzing the effect of viscous dissipation on temperature distribution on the flow of blood plasma through an asymmetric arterial segment. The plasma was considered to be unsteady, laminar and an incompressible fluid through non-uniform arterial segment in a two-dimensional flow. Numerical schemes developed for the coupled partial differential equations governing blood plasma were solved using Finite Difference scheme (FDS). With the aid of the finite difference approach and the related boundary conditions, results for temperature profiles were obtained. The study determined the effect of viscous dissipation on temperature of blood plasma in arteries. The equations were solved using MATLAB softwares and results were presented graphically and in tables. The increase in viscous dissipation tends to decrease blood plasma heat distribution. This study will find important application in hospitals.

Plasma Blobs and Turbulence Impacting Magnetic Confinement(A Short Review)

Space-based plasma(i.e.,a highly ionized gas or the fourth state of matter)blobs are isolated pockets of this highly ionized gas made up of charged particles.These blobs are believed to have a substantial impact on the structure and dynamics of the cosmos and can be seen in a variety of astronomical objects,including stars,galaxies,and the intergalactic medium.Some plasma blobs are connected to intense phenomena like magnetic reconnection,shock waves,and supernovae,while others may be the result of more passive processes like cooling and gravitational collapse.In both astrophysics and plasma physics,there is ongoing research on the characteristics and behavior of plasma blobs.This phenomenon has a very adverse effect on tokamak-based MCF(magnetic confinement fusion),which is the subject of this short review paper.

Evaluating the Effects on Ultrasound and on Magnetic Resonance for Knee Osteoarthritis Treatment by Platelet Rich Plasma Therapy in Combination with Mesenchymal Stem Cells from Autologous Adipose Tissue

Aim: To evaluate the effects based the changes on ultrasound and on magnetic resonance for knee osteoarthritis treatment by platelet-rich plasma therapy in combination with mesenchymal stem cell from autologous adipose tissue. Objects and Methods: 30 patients, 26 females, 4 males, mean age 58.63 ± 11.11, mean disease duration 5.3 ± 4.6 years, respectively 60 knee joints were diagnosed with osteoarthritis at stage II - III according to the Kellgren and Lawrence classifications. After ultrasound and magnetic resonance imaging in the first time, all patients were injected with platelet-rich plasma combined with mesenchymal stem cells from autologous adipose tissue into both knee joints. Results: After treatment 12 months by platelet-rich plasma injection combined with mesenchymal stem cells from autologous adipose tissue: The thickness of articular cartilage on ultrasound increased significantly from 2.08 ± 0.36 mm to 2.48 ± 0.36 mm with p Conclusion: The treatment of knee osteoarthritis by platelet-rich plasma combined with mesenchymal stem cells from autologous adipose tissue was effective in improving cartilage thickness on ultrasound and magnetic resonance, thereby improving the motor function of the knee joint.

Influence of magnetic field on microstructure and properties of Ni60 plasma surfacing layer

In order to control the shape and distribution of hardening phase in plasma surfacing deposit, a longitudinal DC magnetic field was applied during plasma surfacing of nickel-based alloy Ni60. Hardness, wearing resistance, microstructure and phase coastitnent of the plasma surfacing layer were investigated. It was revealed that the hardness and wearing resistance of the Ni60 plasma surfacing layer could gotten significantly enhanced through introducing magnetic field. The mechanical properties of the surfacing deposit were optimal when magnetic field current is 1 A. The metallurgical analysis showed that the microstructure of the Ni60 plasma surfacing layer was mainly composed of γ solid solution and some hardening phase particles such as Cr7C3 with an application of the magnetic field.

Microstructure and magnetic properties of bulk magnets Nd_(14-x)Fe_(76+x)Co_3Zr_1B_6(x=0,0.5,1) prepared by spark plasma sintering

Melt-spun ribbons with nominal composition of Nd14–xFe76+xCo3Zr1B6(x=0,0.5,1) were consolidated into isotropic bulk magnets by spark plasma sintering method.It was found that the Nd content and sintering temperature had significant influence on the density and magnetic properties of the sintered magnets.Homogeneous microstructure and fine grain(50–100 nm) were obtained when sintering below 700 ℃,and the initial magnetization curve showed that the coercivity was controlled by the pinning mechanism.However,ab...

Current–voltage characteristics of hydrogen DC plasma torches with different sizes in an external axial magnetic field

Current-voltage （l-V） characteristics of hydrogen DC plasma torches with different sizes in an external axial magnetic field under atmospheric pressure are reported. Three anodes with different diameters are adopted in a 50-kW torch： 25 mm, 30 mm, and 35 nun, respectively. Two different diameters of anodes, that is, 100 mm and 130 mm, are adopted in a 1-MW plasma torch. The arc voltage shows a negative trend with the increase of arc current under the operating regimes. On the contrary, arc voltage shows a positive trend as the flow rate of carder gas increases, and a similar trend is found with increasing the external magnetic flux density. A similarity formula is constructed to correlate the experimental data of the torches mentioned above. Linear fitting shows that the Pearson correlation coefficient is 0.9958.

Simulation of Magnetically Dispersed Arc Plasma

Magnetically dispersed arc plasma exhibits typically dispersed uniform arc column as well as diffusive cathode root and diffusive anode root. In this paper magnetically dispersed arc plasma coupled with solid cathode is numerically simulated by the simplified cathode sheath model of LOWKE . The numerical simulation results in argon show that the maximum value of arc root current density on the cathode surface is 3.5×10^7 A/m^2）, and the maximum value of energy flux on the cathode surface is 3× 10^7 J/m^2, both values are less than the average values of a contracted arc, respectively.

The magnetic field design of a solenoid for the cold-cathode Penning ion source of a miniature neutron tube

A high-yield and beam-stable neutron tube can be applied in many fields.It is of great significance to the optimal external magnetic field intensity of the cold-cathode Penning ion source(PIS)and precisely controls the movement of deuterium(D),tritium(T)ions and electrons in the source of the neutron tubes.A cold-cathode PIS is designed based on the solenoidal magnetic field to obtain better uniformity of the magnetic field and higher yield of the neutron tube.The degree of magnetic field uniformity among the magnetic block,double magnetic rings and solenoidal ion sources is compared using finite element simulation methods.Using drift diffusion approximation and a magnetic field coupling method,the plasma distribution of hydrogen and the relationship between plasma density and magnetic field intensity at 0.06 Pa pressure and a solenoid magnetic field are obtained.The results show that the solenoidal ion source has the most uniform magnetic field distribution.The optimum magnetic field strength of about 0.1 T is obtained in the ion source at an excitation voltage of 1 V.The maximum average number density of monatomic hydrogen ions(H+)is 1×108 m−3,and an ion-beam current of about 14.51μA is formed under the−5000 V extraction field.The study of the solenoidal magnetic field contributes to the understanding of the particle dynamics within the PIS and provides a reference for the further improvement of the source performance of the neutron tube in the future.

Development of a helicon-wave excited plasma facility with high magnetic field for plasma-wall interactions studies

The high magnetic field helicon experiment system is a helicon wave plasma（HWP）source device in a high axial magnetic field（B0）developed for plasma–wall interactions studies for fusion reactors.This HWP was realized at low pressure（5×10^-3-10 Pa）and a RF（radio frequency,13.56 MHz）power（maximum power of 2 k W）using an internal right helical antenna（5 cm in diameter by 18 cm long）with a maximum B0of 6300 G.Ar HWP with electron density～10^18–10^20m^-3 and electron temperature～4–7 e V was produced at high B0 of 5100 G,with an RF power of 1500 W.Maximum Ar^＋ion flux of 7.8×10^23m^-2s^-1 with a bright blue core plasma was obtained at a high B0 of 2700 G and an RF power of 1500 W without bias.Plasma energy and mass spectrometer studies indicate that Ar^＋ ion-beams of 40.1 eV are formed,which are supersonic（～3.1cs）.The effect of Ar HWP discharge cleaning on the wall conditioning are investigated by using the mass spectrometry.And the consequent plasma parameters will result in favorable wall conditioning with a removal rate of 1.1×10^24N2/m^2 h.

A STUDY OF PLASMA PROPERTIES FOR VARIOUS MAGNETIC FIELDS IN A MICROWAVE MULTIPOLAR ECR PLASMA

A sputtering-type microwave multipolar ECR plasma processing for preparing thin films, is built with Nd-Fe-B magnets and 2.45 GHz, TE10 mode microwave. The plasma distributions in the axial direction, which is important for preparing thin films, are found to be very sensitive to the magnetic potential fields in plasma chamber. The plasma parameters are also influenced by the background gas pressure.

Particle-in-cell simulations of low-β magnetic reconnection driven by laser interaction with a capacitor–coil target

The dynamics of low-β magnetic reconnection(MR) driven by laser interaction with a capacitor–coil target are reexamined by simulations in this paper. We compare two cases MR and non-MR(also referred as AP-case and P-case standing for the anti-parallel and parallel magnetic field lines, respectively) to distinguish the different characteristics between them.We find that only in the AP-case the reconnection electric field shows up around the X line and the electron jet is directed toward the X line. The quadruple magnetic fields exist in both cases, however, they distribute in the current sheet area in the AP-case, and out of the squeezing area in the P-case, because electrons are demagnetized in the electron diffusion region in the MR process, which is absent in the P-case. The electron acceleration is dominant by the Fermi-like mechanism before the MR process, and by the reconnection electric field when the MR occurs. A power-law electron energy spectrum with an index of 1.8 is found in the AP-case. This work proves the significant potential of this experimental platform to be applied in the studies of low-β astronomy phenomena.

An Experimental Platform for the Study on Magnetic Reconnection in Laboratory Plasmas

In order to investigate electron dynamics near the electron diffusion region in mag- netic reconnection process, an upgrade in the linear magnetized plasma （LMP） device is accom- plished at the University of Science and Technology of China. Radio frequency （RF） helicon discharge is used to generate a quasi-stationary plasma, and a time-dependent magnetic field is applied to the plasma, which exhibits an X-type neutral point in vacuum. A two-dimensional sophisticated mobile platform is built up, providing a high spatial resolution, below 0.5 ram, for the diagnostics.

The Influence of Magnetic Field on Antenna Performance in Plasma

A spacecraft loses all forms of communication, including global positioning system signals, data telemetry, voice communication and so on, when it enters the communication blackout phase. This becomes more and more critical with the development of reentry vehicle missions since radio blackout brings about many serious issues related to vehicle safety. This paper studies the influence of magnetic field on antenna performance in plasma. The results indicate that the effect of plasma on the antenna performance can be negligible when the magnetic field reaches a certain strength. This provides another way to solve the reentry blackout problem.