On the Heating of a Pinch

1970 ◽  
Vol 25 (12) ◽  
pp. 1803-1807
Author(s):  
R. Mewe
Keyword(s):  
Magnetic Field ◽  
Heating Rate ◽  
Initial Rate ◽  
Final Value ◽  
Capacitor Banks ◽  
Theta Pinch ◽  
The Magnetic Field ◽  
Compression Temperature

Abstract The compression temperature of a theta pinch is calculated as a function of the circuit para-meters and the final /?-value of the plasma. One of the results is that the temperature, T, at the peak magnetic field, B, scales of (B B) t/s , where B is the initial rate of rise of the magnetic field. A possibility of combining two capacitor banks to increase the implosion heating rate is discussed.

scholarly journals Stochastic proton heating by kinetic-Alfvén-wave turbulence in moderately high- plasmas

2018 ◽  
Vol 84 (6) ◽  
Author(s):  
Ian W. Hoppock ◽  
Benjamin D. G. Chandran ◽  
Kristopher G. Klein ◽  
Alfred Mallet ◽  
Daniel Verscharen
Keyword(s):  
Magnetic Field ◽  
Heating Rate ◽  
Electrostatic Potential ◽  
Alfven Wave ◽  
Average Magnetic Moment ◽  
Kinetic Alfvén Wave ◽  
Stochastic Heating ◽  
Kinetic Alfven Wave ◽  
Time Variations ◽  
The Magnetic Field

Stochastic heating refers to an increase in the average magnetic moment of charged particles interacting with electromagnetic fluctuations whose frequencies are smaller than the particles’ cyclotron frequencies. This type of heating arises when the amplitude of the gyroscale fluctuations exceeds a certain threshold, causing particle orbits in the plane perpendicular to the magnetic field to become stochastic rather than nearly periodic. We consider the stochastic heating of protons by Alfvén-wave (AW) and kinetic-Alfvén-wave (KAW) turbulence, which may make an important contribution to the heating of the solar wind. Using phenomenological arguments, we derive the stochastic-proton-heating rate in plasmas in which $\unicode[STIX]{x1D6FD}_{\text{p}}\sim 1$–30, where $\unicode[STIX]{x1D6FD}_{\text{p}}$ is the ratio of the proton pressure to the magnetic pressure. (We do not consider the $\unicode[STIX]{x1D6FD}_{\text{p}}\gtrsim 30$ regime, in which KAWs at the proton gyroscale become non-propagating.) We test our formula for the stochastic-heating rate by numerically tracking test-particle protons interacting with a spectrum of randomly phased AWs and KAWs. Previous studies have demonstrated that at $\unicode[STIX]{x1D6FD}_{\text{p}}\lesssim 1$, particles are energized primarily by time variations in the electrostatic potential and thermal-proton gyro-orbits are stochasticized primarily by gyroscale fluctuations in the electrostatic potential. In contrast, at $\unicode[STIX]{x1D6FD}_{\text{p}}\gtrsim 1$, particles are energized primarily by the solenoidal component of the electric field and thermal-proton gyro-orbits are stochasticized primarily by gyroscale fluctuations in the magnetic field.

Characterization of an Analytical Theta-Pinch Plasma Generated with a Unidirectional Capacitive Discharge

1988 ◽  
Vol 42 (1) ◽  
pp. 77-83 ◽  
Author(s):  
E. T. Johnson ◽  
R. D. Sacks
Keyword(s):  
Magnetic Field ◽  
Discharge Current ◽  
Discharge Circuit ◽  
Radiative Properties ◽  
Plasma Properties ◽  
Capacitive Discharge ◽  
Zero Crossings ◽  
Theta Pinch ◽  
The Magnetic Field

The plasma produced by a high-current capacitive discharge through a graphite fiber bundle is compressed by a magnetic field coaxial with the plasma. The magnetic field is generated by the plasma current in a large coil surrounding the plasma. The field induces an azimuthal (theta) current in the plasma. This current couples with the external magnetic field and produces a radial Lorentz force which reduces the rate of plasma expansion. A diode shunt in the capacitive discharge circuit is used for the generation of a unidirectional discharge current. This arrangement eliminates zero-crossings of the discharge current and thus increases the effectiveness of the magnetic field in controlling the radiative properties of the plasma. Design features of the discharge circuit are presented, as well as a comparison of the plasma properties with oscillatory and unidirectional discharge current waveforms.

Barrel heating with inductive coils in an injection molding machine

2019 ◽  
Vol 39 (10) ◽  
pp. 934-943
Author(s):  
Shih-Chih Nian ◽  
Gao-Hao Yeh ◽  
Ming-Shyan Huang
Keyword(s):  
Magnetic Field ◽  
Injection Molding ◽  
Heating Rate ◽  
Inductive Heating ◽  
Energy Rate ◽  
Heating Performance ◽  
Time Required ◽  
Spiral Grooves ◽  
The Magnetic Field ◽  
Inductive Coils

Abstract Traditional injection molding machines use resistance heating (RH) bands to heat the barrel. However, RH has a low energy rate; thus, the time required to reach the target temperature is rather long. Consequently, the use of inductive techniques, with a faster heating rate and improved energy rate, has attracted growing interest in recent years. However, an inappropriate design of the inductive coils and plasticization barrel may result in a strong repulsive magnetic field between neighboring coils and a corresponding reduction in the heating performance. Thus, developing an appropriate inductive heating design is essential in improving the barrel heating performance. The present study therefore performed a simulation and experimental investigation into the magnetic field and temperature distribution for different barrel geometries and coil current designs. The simulation results showed that the application of spiral grooves to the barrel improved both the heating rate and the temperature uniformity (TU) and effectively solved the proximity effect. The results indicated that the application of induction heating together with a novel grooved barrel design yields an effective improvement in both the thermal efficiency and the TU compared to that achieved using the traditional RH method with a single- or double-section barrel.

Topology of the Magnetic Field and Resistivity of a Compact Torus Generated in a Mirrorless Theta Pinch

2019 ◽  
Vol 49 (2) ◽  
pp. 191-197
Author(s):  
Milton E. Kayama ◽  
Thiago J. Michelin ◽  
Luiz C. Nascimento
Keyword(s):  
Magnetic Field ◽  
Theta Pinch ◽  
Compact Torus ◽  
The Magnetic Field

scholarly journals Time-Resolved Profile Measurements of Impurity Lines in a Theta Pinch Discharge

1965 ◽  
Vol 20 (11) ◽  
pp. 1375-1385 ◽  
Author(s):  
A. Eberhagen ◽  
M. J. Bernstein ◽  
H. Hermansdorfer
Keyword(s):  
Magnetic Field ◽  
Line Emission ◽  
Zeeman Splitting ◽  
Line Broadening ◽  
Image Converter ◽  
Combined System ◽  
Time Resolved ◽  
Theta Pinch ◽  
Fabry Perot ◽  
The Magnetic Field

Line profile measurements were carried out on a small theta pinch experiment in order to get information on the ion motions during the discharge. A FABRY-PEROT interferometer combined with a so-called Fafnir arrangement was used for measuring the shape of the investigated N V (4603 Å) and O VI (3811 Å) lines. The additional use of a polarizer and λ/4 plate made it possible to eliminate ZEEMAN splitting caused by a magnetic field present, which affects the line shape, and to measure the magnitude of the magnetic field strength at the site of line emission in the plasma. By means of a combined system comprising image converter and intensifier the emission regions of the investigated lines in the plasma could be identified. The experimentally obtained results are discussed considering the different influences leading to line broadening in the present experiment.

Heating of a Theta-Pinch Plasma by a CO2 Laser

1971 ◽  
Vol 49 (12) ◽  
pp. 1685-1687 ◽  
Author(s):  
J. Martineau ◽  
H. Pépin
Keyword(s):  
Magnetic Field ◽  
Laser Pulse ◽  
Pulse Duration ◽  
Co2 Laser ◽  
Magnetic Confinement ◽  
Deuterium Plasma ◽  
Ion Temperature ◽  
Theta Pinch ◽  
Absorbed Power ◽  
The Magnetic Field

The heating of a theta-pinch deuterium plasma by a CO2 laser has been studied as a function of pulse duration and energy. A hydrodynamical approach was used with temperatures and densities assumed uniform in a fully ionized plasma. This model takes into account the dynamics of the magnetic field, the axial and radial magnetic confinement, the shape of the laser pulse, and energy transferred to the plasma by inverse bremsstrahlung. We discuss the results (dimensions, temperature, absorbed power) snowing that an increase in pulse duration results in higher electron and ion temperature.

Observing the galactic magnetic field

1967 ◽  
Vol 31 ◽  
pp. 375-380
Author(s):  
H. C. van de Hulst
Keyword(s):  
Magnetic Field ◽  
Fair Agreement ◽  
Solar Neighbourhood ◽  
Galactic Magnetic Field ◽  
The Magnetic Field

Various methods of observing the galactic magnetic field are reviewed, and their results summarized. There is fair agreement about the direction of the magnetic field in the solar neighbourhood:l= 50° to 80°; the strength of the field in the disk is of the order of 10-5gauss.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ultra Violet ◽  
Active Regions ◽  
Morphological Properties ◽  
Energy Storage And Conversion ◽  
The Sun ◽  
X Rays ◽  
The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

On the Configuration of the Magnetic Field of β CrB

1976 ◽  
Vol 32 ◽  
pp. 613-622
Author(s):  
I.A. Aslanov ◽  
Yu.S. Rustamov
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Radial Velocity ◽  
Magnetic Field Strength ◽  
Complex Shape ◽  
Rotation Period ◽  
Field Variation ◽  
Magnetic Field Variation ◽  
Secular Variations ◽  
The Magnetic Field

SummaryMeasurements of the radial velocities and magnetic field strength of β CrB were carried out. It is shown that there is a variability with the rotation period different for various elements. The curve of the magnetic field variation measured from lines of 5 different elements: FeI, CrI, CrII, TiII, ScII and CaI has a complex shape specific for each element. This may be due to the presence of magnetic spots on the stellar surface. A comparison with the radial velocity curves suggests the presence of a least 4 spots of Ti and Cr coinciding with magnetic spots. A change of the magnetic field with optical depth is shown. The curve of the Heffvariation with the rotation period is given. A possibility of secular variations of the magnetic field is shown.

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