Nonstationary theory of mode competition in gyrotrons with allowance for small inhomogeneity of the guiding magnetic field

1994 ◽  
Vol 76 (9) ◽  
pp. 5580-5585 ◽  
Author(s):  
O. Dumbrajs
Keyword(s):  
Magnetic Field ◽  
Mode Competition ◽  
Nonstationary Theory ◽  
Small Inhomogeneity

Mode competition in a gas laser tuned by an axial magnetic field

1986 ◽  
Vol 16 (7) ◽  
pp. 968-971
Author(s):  
V S Afanas'ev ◽  
A Ch Izmaĭlov ◽  
V D Mironov
Keyword(s):  
Magnetic Field ◽  
Axial Magnetic Field ◽  
Mode Competition ◽  
Gas Laser

Mode competition in a gyrotron with tapered external magnetic field

1988 ◽  
Vol 64 (1) ◽  
pp. 137-145 ◽  
Author(s):  
O. DUMBRAJS ◽  
G. S. NUSINOVICH ◽  
A. B. PAVELYEV
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Mode Competition

ON THE OSCILLATIONS OF A WEAKLY INHOMOGENEOUS PLASMA

1965 ◽  
Vol 43 (4) ◽  
pp. 640-644
Author(s):  
Som Krishan
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Wave Vector ◽  
Inhomogeneous Plasma ◽  
Collisionless Plasma ◽  
Velocity Distribution Function ◽  
One Dimension ◽  
Larmor Radius ◽  
Small Inhomogeneity ◽  
Inhomogeneity Parameter

Oscillations of a collisionless plasma in equilibrium with a magnetic field which is weakly inhomogeneous in one dimension are studied. The calculations are based on longitudinal oscillations, i.e. the electric vector is parallel to the wave vector. The procedure employed is to use Maxwell's equations and expand the velocity distribution function about its equilibrium value for finding the perturbation in the distribution. The dispersion relation so obtained is different from that of Rosenbluth et al. (1962). The system is stable for the small Landau growth rate (Landau 1946), which might become appreciable for wavelengths comparable with the Larmor radius, provided [Formula: see text], where k is the wave vector and ε is a small inhomogeneity parameter.

Nonlinear dynamics of low-frequency drift waves

1996 ◽  
Vol 55 (1) ◽  
pp. 3-23 ◽  
Author(s):  
M. Beckmann ◽  
P. Frank ◽  
G. Himmel
Keyword(s):  
Magnetic Field ◽  
Opposite Sign ◽  
Low Frequency ◽  
Temperature Gradients ◽  
Mode Competition ◽  
Drift Waves ◽  
Nonlinear Behaviour ◽  
Nonlinear Features ◽  
Electron Density And Temperature ◽  
Low Frequency Waves

The nonlinear behaviour of unstable drift waves in magnetized plasmas is analysed analytically. Most attention is paid to low-frequency waves created in electron density and temperature gradients of opposite sign. This situation is typically encountered in radiofrequency-produced discharges. The model developed explains nonlinear features such as mode competition, amplitude saturation and magnetic field hysteresis, which are observed experimentally.

Axial modes in terahertz high-harmonic large-orbit gyrotrons

2019 ◽  
Vol 33 (14n15) ◽  
pp. 1940008
Author(s):  
Yi Sheng Yeh ◽  
Cong-Yuan Zheng ◽  
Li-Jhen Li ◽  
Po-Yi Chiang ◽  
Yen-Cheng Chen ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Applied Magnetic Field ◽  
High Harmonic ◽  
Mode Competition ◽  
Velocity Spread ◽  
Axial Mode ◽  
Third Harmonic ◽  
Large Orbit Gyrotron ◽  
Text Mode

Terahertz (THz) gyrotrons can operate with a lower applied magnetic field in harmonic operation, but the weakened harmonic interactions in harmonic gyrotrons can introduce serious challenges when mode competition occurs. The use of an axis-encircling electron beam can greatly alleviate mode competition in a harmonic gyrotron. In this paper, we study axial modes for third-harmonic [Formula: see text]-mode large-orbit gyrotrons. Simulation results reveal that the minimum current for oscillation to begin in each axial mode in the gyrotron regime is associated with a specific range of applied magnetic field. To avoid mode competition, tapered applied magnetic fields and waveguide radii are employed to enhance the high-order axial modes and suppress the low-order axial modes. Furthermore, spurious transverse modes in a THz gyrotron are discussed below. A stable third-harmonic [Formula: see text]-mode large-orbit gyrotron at the third-order axial mode is predicted to yield peak output power of 6.5 kW at 768.1 GHz with an efficiency of 10% for a 75-kV, 0.85-A electron beam with an axial velocity spread of 3%.

Magnetic-field strengths from optical polarization data

1967 ◽  
Vol 31 ◽  
pp. 381-383
Author(s):  
J. M. Greenberg
Keyword(s):  
Magnetic Field ◽  
Optical Polarization ◽  
Polarization Data ◽  
Term Model ◽  
Source Of Information ◽  
Field Strengths

Van de Hulst (Paper 64, Table 1) has marked optical polarization as a questionable or marginal source of information concerning magnetic field strengths. Rather than arguing about this–I should rate this method asq+-, or quarrelling about the term ‘model-sensitive results’, I wish to stress the historical point that as recently as two years ago there were still some who questioned that optical polarization was definitely due to magnetically-oriented interstellar particles.

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.

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