The HelCat basic plasma science device

2014 ◽  
Vol 81 (1) ◽  
Author(s):  
M. Gilmore ◽  
A. G. Lynn ◽  
T. R. Desjardins ◽  
Y. Zhang ◽  
C. Watts ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Axial Magnetic Field ◽  
Medium Size ◽  
Plasma Parameters ◽  
Plasma Sources ◽  
Plasma Gun ◽  
Background Magnetic Field ◽  
Wide Range ◽  
Plasma Science ◽  
Helicon Source

TheHelicon-Cathode(HelCat) device is a medium-size linear experiment suitable for a wide range of basic plasma science experiments in areas such as electrostatic turbulence and transport, magnetic relaxation, and high power microwave (HPM)-plasma interactions. The HelCat device is based on dual plasma sources located at opposite ends of the 4 m long vacuum chamber – an RF helicon source at one end and a thermionic cathode at the other. Thirteen coils provide an axial magnetic fieldB⩾ 0.220 T that can be configured individually to give various magnetic configurations (e.g. solenoid, mirror, cusp). Additional plasma sources, such as a compact coaxial plasma gun, are also utilized in some experiments, and can be located either along the chamber for perpendicular (to the background magnetic field) plasma injection, or at one of the ends for parallel injection. Using the multiple plasma sources, a wide range of plasma parameters can be obtained. Here, the HelCat device is described in detail and some examples of results from previous and ongoing experiments are given. Additionally, examples of planned experiments and device modifications are also discussed.

Long-pulse plasma source for SMOLA helical mirror

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Ivan A. Ivanov ◽  
V. O. Ustyuzhanin ◽  
A. V. Sudnikov ◽  
A. Inzhevatkina
Keyword(s):  
Magnetic Field ◽  
Gas Flow ◽  
Supply Voltage ◽  
Hydrogen Plasma ◽  
Plasma Source ◽  
Lanthanum Hexaboride ◽  
Plasma Stream ◽  
Plasma Parameters ◽  
Plasma Properties ◽  
Plasma Gun

A plasma gun for forming a plasma stream in the open magnetic mirror trap with additional helicoidal field SMOLA is described. The plasma gun is an axisymmetric system with a planar circular hot cathode based on lanthanum hexaboride and a hollow copper anode. The two planar coils are located around the plasma source and create a magnetic field of up to 200 mT. The magnetic field forms the magnetron configuration of the discharge and provides a radial electric insulation. The source typically operates with a discharge current of up to 350 A in hydrogen. Plasma parameters in the SMOLA device are Ti ~ 5 eV, Te ~ 5–40 eV and ni ~ (0.1–1)  × 1019 m−3. Helium plasma can also be created. The plasma properties depend on the whole group of initial technical parameters: the cathode temperature, the feeding gas flow, the anode-cathode supply voltage and the magnitude of the cathode magnetic insulation.

HelioSwarm: The Nature of Turbulence in Space Plasmas

2021 ◽  
Author(s):  
Harlan Spence ◽  
Kristopher Klein ◽  
HelioSwarm Science Team
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Large Scale ◽  
Solar Wind Plasma ◽  
Turbulent Energy ◽  
Space Plasmas ◽  
Plasma Parameters ◽  
Astrophysical Plasmas ◽  
Ion Distributions ◽  
Background Magnetic Field

<p>Recently selected for phase A study for NASA’s Heliophysics MidEx Announcement of Opportunity, the HelioSwarm Observatory proposes to transform our understanding of the physics of turbulence in space and astrophysical plasmas by deploying nine spacecraft to measure the local plasma and magnetic field conditions at many points, with separations between the spacecraft spanning MHD and ion scales.  HelioSwarm resolves the transfer and dissipation of turbulent energy in weakly-collisional magnetized plasmas with a novel configuration of spacecraft in the solar wind. These simultaneous multi-point, multi-scale measurements of space plasmas allow us to reach closure on two science goals comprised of six science objectives: (1) reveal how turbulent energy is transferred in the most probable, undisturbed solar wind plasma and distributed as a function of scale and time; (2) reveal how this turbulent cascade of energy varies with the background magnetic field and plasma parameters in more extreme solar wind environments; (3) quantify the transfer of turbulent energy between fields, flows, and ion heat; (4) identify thermodynamic impacts of intermittent structures on ion distributions; (5) determine how solar wind turbulence affects and is affected by large-scale solar wind structures; and (6) determine how strongly driven turbulence differs from that in the undisturbed solar wind. </p>

Resistive MHD modes in hollow cathodes external plasma

2021 ◽  
Author(s):  
Giulia Becatti ◽  
Francesco Burgalassi ◽  
Fabrizio Paganucci ◽  
Matteo Zuin ◽  
Dan M Goebel
Keyword(s):  
Magnetic Field ◽  
Hollow Cathode ◽  
Electric Propulsion ◽  
Axial Magnetic Field ◽  
Mhd Equations ◽  
Linear Perturbation ◽  
Plasma Parameters ◽  
Hollow Cathodes ◽  
Plume Region ◽  
Helical Mode

Abstract A significant number of plasma instabilities occur in the region just outside of hollow cathodes, depending on the injected gas flow, the current level and the application of an external magnetic field. In particular, the presence of an axial magnetic field induces a helical mode, affecting all the plasma parameters and the total current transported by the plasma. To explore the onset and behavior of this helical mode, the fluctuations in the plasma parameters in the current-carrying plume outside of a hollow cathode discharge have been investigated. The hollow cathode was operated at a current of 25 A, and at variable levels of propellant flow rate and applied magnetic fields. Electromagnetic probes were used to measure the electromagnetic fluctuations, and correlation analysis between each of the probe signals provided spatial-temporal characterization of the generated waves. Time-averaged plasma parameters, such as plasma potential and ion energy distribution function, were also collected in the near-cathode plume region by means of scanning emissive probe and retarding potential analyzer. The results show that the helical mode exists in the cathode plume at sufficiently high applied magnetic field, and is characterized by the presence of a finite electromagnetic component in the axial direction, detectable at discharge currents $\geq$ 25 A. A theoretical analysis of this mode reveals that one possible explanation is consistent with the hypotheses of resistive magnetohydrodynamics, which predicts the presence of helical modes in the forms of resistive kink. The analysis has been carried out by linear perturbation of the resistive MHD equations, from which it is possible to obtain the dispersion relation of the mode and find the $k-\omega$ unstable branch associated with the instability. These findings provided the basis for more detailed investigation of resistive MHD modes and their effect in the plume of hollow cathodes developed for electric propulsion application.

scholarly journals Measurement of Some Argon Plasma Parameters Glow Discharge Under Axial Magnetic Field

2019 ◽  
Vol 7 (4) ◽  
pp. 158-166
Author(s):  
Pshtiwan M.A. Karim ◽  
Diyar S. Mayi ◽  
Shamo Kh. Al-Hakary
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Glow Discharge ◽  
Electron Temperature ◽  
Breakdown Voltage ◽  
Axial Magnetic Field ◽  
Argon Plasma ◽  
Emission Lines ◽  
Plasma Parameters ◽  
Gas Pressures

This paper investigates the characteristics some of argon plasma parameters of glow discharge under axial magnetic field. The DC power supply of range (0-6000) V is used as a breakdown voltage to obtain the discharge of argon gas. The discharge voltage-current (V-I) characteristic curves and Paschen’s curves as well as the electrical conductivity were studied with the presents of magnetic field confinement at different gas pressures. The magnetic field up to 25 mT was obtained using four coils of radius 6 cm and 320 turn by passing A.C current up to 5 Amperes. Spectroscopic measurements are employed for purpose of estimating two main plasma parameters electron temperature (Te) and electron density (ne). Emission spectra from positive column (PC) zone of the discharge have been studies at different values of magnetic field and pressures at constant discharge currents of 1.5 mA. Electron temperature (Te) and its density are calculated from the ratio of the intensity of two emission lines of the same lower energy levels. Experimental results show the abnormal glow region characteristics (positive resistance). Breakdown voltage versus pressure curves near the curves of paschen and decrease as magnetic field increases due to magnetic field confinement of plasma charged particles. Also the electrical conductivity increases due to enhancing magnetic field at different gas pressures. Both temperature density of electron and the intensities of two selected emission lines decrease with increasing pressure due decreasing of mean free path of electron. Electron density increase according to enhancing magnetic field, while the intensity of emitting lines tends to decrease.

Stability of hydromagnetic dissipative Couette flow with non-axisymmetric disturbance

1998 ◽  
Vol 366 ◽  
pp. 135-158 ◽  
Author(s):  
CHA'O-KUANG CHEN ◽  
MIN HSING CHANG
Keyword(s):  
Magnetic Field ◽  
Couette Flow ◽  
Hartmann Number ◽  
Axial Magnetic Field ◽  
Outer Cylinder ◽  
Numerical Procedure ◽  
Stationary Mode ◽  
Instability Modes ◽  
Wide Range ◽  
Axisymmetric Instability

A linear stability analysis has been implemented for hydromagnetic dissipative Couette flow, a viscous electrically conducting fluid between rotating concentric cylinders in the presence of a uniform axial magnetic field. The small-gap equations with respect to non-axisymmetric disturbances are derived and solved by a direct numerical procedure. Both types of boundary conditions, conducting and non-conducting walls, are considered. A parametric study covering wide ranges of μ, the ratio of angular velocity of the outer cylinder to that of inner cylinder, and Q, the Hartmann number which represents the strength of axial magnetic field, is conducted. Results show that the stability characteristics depend on the conductivity of the cylinders. For the case of non-conducting walls, it is found that the critical disturbance is a non-axisymmetric mode as the value of μ is sufficiently negative and the domain of Q where non-axisymmetric instability modes prevail is limited. Similar results are obtained for conducting walls at low Hartmann number. In addition, the transition of the onset of instability from non-axisymmetric modes to axisymmetric modes for the case μ=−1 with increasing strength of magnetic field are discussed in detail. For high values of the Hartmann number, the critical disturbance is always the axisymmetric stationary mode for non-conducting walls but not for conducting walls. For −1[les ]μ<1, it is demonstrated that non-axisymmetric instability modes prevail in a wide range of Q for conducting walls and axisymmetric oscillatory modes may, in fact, become more critical than both of the non-axisymmetric and axisymmetric stationary modes at higher values of the Hartmann number.

Seebeck effect studies in the charge density wave state of organic conductor α −(BEDT −TTF)2KHg(SCN)4

2021 ◽  
Author(s):  
Danica Krstovska ◽  
Eun Sang Choi ◽  
Eden Steven
Keyword(s):  
Magnetic Field ◽  
Fermi Surface ◽  
Temperature Dependence ◽  
Density Wave ◽  
Transport Processes ◽  
Seebeck Effect ◽  
Complex Nature ◽  
Organic Conductor ◽  
Background Magnetic Field ◽  
Wide Range

Abstract Angular, magnetic field and temperature dependence of the interlayer Seebeck effect of the multiband organic conductor α −(BEDT −TTF)2KHg(SCN)4 is experimentally studied at temperatures down to 0.55 K and fields up to 31 T in a wide range of angles. The background magnetic field and angular component of the Seebeck effect as well as the magnetic quantum oscillations that originate from the closed Fermi surface orbits are analyzed. The background interlayer Seebeck effect components show that above certain tilt angle of the magnetic field and above the kink field there is another CDW state in α −(BEDT −TTF)2KHg(SCN)4, between previously known CDW0 and CDWx states, in agreement with magnetoresistance and magnetization studies in this material. Our observations show that this state possesses some of the properties of the CDW0 state. The Fermi surface in the third CDW state is still reconstructed but less imperfectly nested as expected as this state develops above the kink field. The temperature dependence of the interlayer Seebeck effect reveals that this state is developed at temperatures below 3 K and at field orientations around the second AMRO maximum. In addition, for the first time, a detailed T−θ phase diagram of α − (BEDT − TTF)2KHg(SCN)4 based purely on Seebeck effect measurements is presented. We find that other states and transitions, beside the CDW states, also exist in a given temperature and angular range that have not been previously reported. These observations change the whole picture about the transport processes in the organic conductor α −(BEDT −TTF)2KHg(SCN)4 and allow to better understand the complex nature of the CDW order in this and similar compounds.

Experimental study of fast hydromagnetic waves in an argon plasma

1964 ◽  
Vol 278 (1373) ◽  
pp. 243-255 ◽  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Axial Magnetic Field ◽  
Argon Plasma ◽  
Wave Number ◽  
Axially Symmetric ◽  
Plasma Parameters ◽  
Quantitative Evidence ◽  
Hydromagnetic Waves

In these experiments fast hydromagnetic waves are excited by discharging a capacitor through a single turn coil surrounding a cylindrical column of magnetized argon plasma. The plasma column is 200 cm long and 22 cm in diameter, and the axial magnetic field strength is varied in the range from 1 to 6 kG. The wave amplitude is typically 10 G, and the frequency is varied between 1.2 and 6 times the ion cyclotron frequency. Measurement of the radial variation and the relative amplitudes of the three components of the wave magnetic field shows that the oscillation is the lowest axially-symmetric mode. As predicted by the theory, the wave is elliptically polarized in the rθ plane with the magnetic vector rotating in the same sense as the electron cyclotron rotation. The experimental results demonstrate the cut-off of this mode both as the frequency is decreased and as the axial magnetic field strength is increased. Measurements of the axial wave number and absorption coefficient are in good numerical agreement with theoretical dispersion curves computed from the measured plasma parameters. This work provides quantitative evidence to support the theories currently used in treating hydromagnetic oscillations, both stable and unstable, of magnetized plasmas.

scholarly journals Electrostatic Waves with Rapid Frequency Shifts in the Solar Wind Sunward of 1/3 AU

2021 ◽  
Author(s):  
Lily Kromyda ◽  
David M. Malaspina ◽  
Robert E. Ergun ◽  
Jasper Halekas ◽  
Michael L. Stevens ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Plasma Wave ◽  
Detection Algorithm ◽  
Space Physics ◽  
University Of California ◽  
Magnetic Fluctuations ◽  
Plasma Parameters ◽  
University Of Colorado ◽  
Background Magnetic Field

&lt;p&gt;During its first five orbits, the FIELDS plasma wave investigation on board Parker Solar Probe (PSP)&amp;#160; has observed a multitude of plasma waves, including electrostatic whistler and electron Bernstein waves (Malaspina et al. 2020), sunward propagating whistlers (Agapitov et al. 2020), ion-scale electromagnetic waves (Verniero et al. 2020, Bowen et al. 2020) and Alfven, slow and fast mode waves (Chaston et al. 2020).&lt;/p&gt;&lt;p&gt;The importance of these waves lies in their potential to redistribute the energy of the solar wind among different particles species (wave-particle interactions) or different types of waves (wave-wave interactions). The abundance of waves and instabilities observed with PSP points to their central role in the regulation of this energy exchange.&lt;/p&gt;&lt;p&gt;Here we present first observations of an intermittent, electrostatic and broadband plasma wave that is ubiquitous in the range of distances that PSP has probed so far. A unique feature of these waves (FDWs) is a frequency shift that occurs on millisecond timescales. In the frame of the spacecraft, FDWs usually appear between the electron cyclotron and electron plasma frequencies.&lt;/p&gt;&lt;p&gt;We develop a detection algorithm that identifies the FDWs in low cadence spectra. We analyze them using various statistical techniques. We establish their phenomenology and compare the magnetic fluctuations of the background magnetic field at times of FDWs and at times without FDWs. We establish their polarization with respect to the background magnetic field and search for correlations with various plasma parameters and features in the electron, proton and alpha particle distribution moments. We also investigate possible plasma wave modes that could be responsible for the growth of FDWs and the instability mechanisms that could be generating them.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Lily Kromyda*&lt;sup&gt;(1)&lt;/sup&gt;, David M. Malaspina &lt;sup&gt;(1,2)&lt;/sup&gt;, Robert E. Ergun&lt;sup&gt;(1,2) &lt;/sup&gt;, Jasper Halekas&lt;sup&gt;(3)&lt;/sup&gt;, Michael L. Stevens&lt;sup&gt;(4) &lt;/sup&gt;, Jennifer Verniero&lt;sup&gt;(5)&lt;/sup&gt;, Alexandros Chasapis&lt;sup&gt;(2) &lt;/sup&gt;, Daniel Vech&lt;sup&gt;(2) &lt;/sup&gt;, Stuart D. Bale&lt;sup&gt;(5,6) &lt;/sup&gt;, John W. Bonnell&lt;sup&gt;(5) &lt;/sup&gt;, Thierry Dudok de Wit&lt;sup&gt;(7) &lt;/sup&gt;, Keith Goetz&lt;sup&gt;(8) &lt;/sup&gt;, Katherine Goodrich&lt;sup&gt;(5) &lt;/sup&gt;, Peter R. Harvey&lt;sup&gt;(5) &lt;/sup&gt;, Robert J. MacDowall&lt;sup&gt;(9) &lt;/sup&gt;, Marc Pulupa&lt;sup&gt;(5) &lt;/sup&gt;, Anthony W. Case&lt;sup&gt;(4) &lt;/sup&gt;, Justin C. Kasper&lt;sup&gt;(10) &lt;/sup&gt;, Kelly E. Korreck&lt;sup&gt;(4) &lt;/sup&gt;, Davin Larson&lt;sup&gt;(5) &lt;/sup&gt;, Roberto Livi&lt;sup&gt;(5) &lt;/sup&gt;, Phyllis Whittlesey&lt;sup&gt;(5)&lt;/sup&gt;&lt;/p&gt;&lt;p&gt;(1) Astrophysical and Planetary Sciences Department, University of Colorado, Boulder, CO, USA&lt;/p&gt;&lt;p&gt;(2) Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA&lt;/p&gt;&lt;p&gt;(3) &amp;#160;University of Iowa, Iowa City, IA, USA&lt;/p&gt;&lt;p&gt;(4) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA&lt;/p&gt;&lt;p&gt;(5) &amp;#160;Space Sciences Laboratory, University of California, Berkeley, CA, USA&lt;/p&gt;&lt;p&gt;(6) Physics Department, University of California, Berkeley, CA, USA&lt;/p&gt;&lt;p&gt;(7) &amp;#160;LPC2E, CNRS, and University of Orleans, Orleans, France&lt;/p&gt;&lt;p&gt;(8) &amp;#160;School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA&lt;/p&gt;&lt;p&gt;(9) &amp;#160;NASA Goddard Space Flight Center, Greenbelt, MD, USA&lt;/p&gt;&lt;p&gt;(10) University of Michigan, Ann Arbor, MI, USA&lt;/p&gt;

scholarly journals 2D numerical modeling of pulsed plasma acceleration by a magnetic field

2000 ◽  
Vol 18 (2) ◽  
pp. 269-273
Author(s):  
A.A. KONDRATYEV
Keyword(s):  
Magnetic Field ◽  
Numerical Study ◽  
Initial Distribution ◽  
Mhd Equations ◽  
Pulsed Plasma ◽  
Plasma Acceleration ◽  
Plasma Parameters ◽  
Current Channel ◽  
Plasma Gun ◽  
Neutral Gas

Pulsed plasma guns are used to obtain high-velocity (107–108 cm/s) plasma flows. Their performance is restricted by an instability of the plasma acceleration by a magnetic field. This paper presents results of a 2D numerical study of plasma dynamics in the plasma gun. The ZENIT-2D code solving the magnetohydrodynamic (MHD) equations on a fixed Eulerian mesh is used. The plasma parameters and geometry are chosen to be close to the parameters of the MK-200 installation (Sidnev et al., 1983). The influence of the initial distribution of a neutral gas on accelerator performance is investigated. A brief description of the code and details of the simulations are presented. It is shown that the instability of acceleration leads to turbulent mixing of the plasma and magnetic field and, correspondingly, to a broader current channel than that predicted by the classical diffusion with the Spitzer conductivity. Numerical results are compared with experimental data (Bakhtin & Zhitlukhin, 1998) displaying a good qualitative agreement.

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