DIFFERENCE FREQUENCY HARMONIC ION HEATING

1967 ◽  
Vol 45 (5) ◽  
pp. 1771-1781 ◽  
Author(s):  
C. R. James ◽  
W. B. Thompson
Keyword(s):  
High Frequency ◽  
Collision Frequency ◽  
Difference Frequency ◽  
Fourth Power ◽  
Heating Process ◽  
Ion Heating ◽  
Frequency Signal ◽  
Transverse Waves ◽  
The Difference ◽  
Frequency Harmonic

The heating of a magnetized hot diffuse plasma using the difference frequency signal generated from two high-frequency (35 GHz) transverse waves is examined. The plasma is described by the cold plasma model and a series expansion of harmonics is used to obtain a solution to the equations. It is shown that the energy absorbed by the ions can be made inversely proportional to the collision frequency and the fourth power of the driven frequency and proportional to the fourth power of the driven electric field intensity. An investigation of the sensitivity of the heating process to fluctuations in frequency, density, and d-c. magnetic field is carried out.

Parametric decay of a whistler wave at the difference frequency of two electromagnetic waves in a plasma

1991 ◽  
Vol 45 (1) ◽  
pp. 115-123 ◽  
Author(s):  
S. Guha ◽  
Ruby Sarkar
Keyword(s):  
Electromagnetic Waves ◽  
Low Frequency ◽  
Whistler Wave ◽  
Difference Frequency ◽  
Lower Hybrid ◽  
Ion Heating ◽  
Lower Hybrid Wave ◽  
Electromagnetic Pump ◽  
The Difference ◽  
Pump Waves

A large-amplitude whistler wave excited at the difference frequency of two high-frequency electromagnetic pump waves is shown to decay parametrically into a lower-hybrid wave (LHW) and a low-frequency ion–Bernstein wave (IBW) in a collisionless magnetized multi-ion-species plasma,. A nonlinear dispersion relation describing this parametric interaction process is derived. The low-frequency ponderomotive force along the direction of the external magnetic field leads to the dominant coupling. Possible applications to ion heating in the ionosphere, in the earth's magnetosphere and in laboratory plasmas are discussed.

Difference frequency harmonic ion heating using Whistler modes

1970 ◽  
Vol 48 (11) ◽  
pp. 1386-1409 ◽  
Author(s):  
C. E. Capjack ◽  
C. R. James
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Kinetic Equations ◽  
Magnetized Plasma ◽  
Natural Mode ◽  
Heating Process ◽  
Ion Heating ◽  
Mixed Wave ◽  
Nonlinear Mixing ◽  
Frequency Harmonic

The heating of ions in a magnetized plasma by the second-order electric fields generated through the nonlinear mixing of two Whistler modes is examined. The kinetic equations describing the mixing and heating process are solved using the method of orbit integrations. Two techniques are available for optimizing the energy absorbed by the ions. One is to allow the mixed wave to approach a natural mode in the plasma, resulting in a field resonance. A second method is to have the ions absorb energy through cyclotron damping. The latter technique and the combination of the two optimizing schemes will be investigated. The resulting sensitivities to fluctuations in frequency, density, static magnetic field, and the direction of propagation of the source waves will be given.

scholarly journals Observation of Ion Heating Using the Difference Frequency of Two ICRF Waves in GAMMA 10/PDX

2021 ◽  
Vol 16 (0) ◽  
pp. 2402045-2402045
Author(s):  
Hiroki KAYANO ◽  
Seowon JANG ◽  
Mafumi HIRATA ◽  
Naomichi EZUMI ◽  
Hibiki YAMAZAKI ◽  
...  
Keyword(s):  
Difference Frequency ◽  
Ion Heating ◽  
The Difference

Comparison of In-the-Ear and Over-the-Ear Hearing Aid Fittings

1986 ◽  
Vol 51 (4) ◽  
pp. 362-369 ◽  
Author(s):  
Donna M. Risberg ◽  
Robyn M. Cox
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Comparative Evaluation ◽  
Speech Intelligibility ◽  
Hearing Aid ◽  
Hearing Aid Fitting ◽  
The Difference ◽  
Functional Gain ◽  
The Relationship

A custom in-the-ear (ITE) hearing aid fitting was compared to two over-the-ear (OTE) hearing aid fittings for each of 9 subjects with mild to moderately severe hearing losses. Speech intelligibility via the three instruments was compared using the Speech Intelligibility Rating (SIR) test. The relationship between functional gain and coupler gain was compared for the ITE and the higher rated OTE instruments. The difference in input received at the microphone locations of the two types of hearing aids was measured for 10 different subjects and compared to the functional gain data. It was concluded that (a) for persons with mild to moderately severe hearing losses, appropriately adjusted custom ITE fittings typically yield speech intelligibility that is equal to the better OTE fitting identified in a comparative evaluation; and (b) gain prescriptions for ITE hearing aids should be adjusted to account for the high-frequency emphasis associated with in-the-concha microphone placement.

scholarly journals Hyperfine structure in the arc spectrum of cæsium and nuclear rotation

1928 ◽  
Vol 121 (787) ◽  
pp. 432-447 ◽  
Keyword(s):  
Hyperfine Structure ◽  
Nuclear Spin ◽  
High Frequency ◽  
Principal Series ◽  
Very High Frequency ◽  
Nuclear Rotation ◽  
Higher Temperature ◽  
The Difference ◽  
Mechanical Moment ◽  
Very High

The arc spectrum of cæsium was investigated with the object of finding whether any of its lines possessed hyperfine structure, resulting from a nuclear magnetic moment, due to a quantised nuclear spin. The lines belonging to the principal series should, owing to the greater degree of penetration of the electron in the (1 s or 6 1 ) orbit, and the correspondingly greater interaction, show the greatest effect. The lines of the principal series are very easily broadened if the vapour pressure of the metal becomes high, so that great care had to be used in obtaining the spectrum of cæsium at a sufficiently low temperature. The most satisfactory method of excitation was found to be the application by means of external electrodes of a very high frequency alternating current to a tube filled with helium at about 2 mm. pressure containing a small quantity of cæsium. The tube required slight heating to bring out the cæsium lines; without this the helium spectrum was very much stronger than the metallic spectrum. At a very low vapour pressures of cæsium the discharge was blue in colour. Under these conditions the lines of the principal series showed no broadening greater than that due to thermal agitation, but at a slightly higher temperature the colour of the discharge became purple and the lines broadened. The lines belonging to the principal series were found to be very close doublets with very nearly constant frequencies differences. A theory is worked out which explains the origin of these doublets, assuming a nuclear spin of one half quantum; by correlating the difference in the separation of the hyperfine structure doublets in the 1 s — m 2 p 3/2 lines and the 1 s — m 2 p 1/2 lines, it is shown that a ratio of the magnetic to the mechanical moment of the nucleus about twice as great as the corresponding ratio for the electron would account for the observed frequency differences. The spectral notation used throughout is that of Hund. The results are compared with those found for the hyperfine structure of some of the bismuth lines by Back and Goudsmid, and are found to be in satisfactory agreement. A selection principle is found which applies both to the bismuth and the cæsium spectrum.

Effective coffision frequency and electron temperature in a weakly ionized argon plasma

1980 ◽  
Vol 23 (2) ◽  
pp. 271-282
Author(s):  
C. P. Schneider
Keyword(s):  
Electron Temperature ◽  
High Frequency ◽  
Collision Frequency ◽  
Argon Plasma ◽  
Angular Frequency ◽  
Weak Electric Field ◽  
Hard Sphere Model ◽  
Plasma Conductivity ◽  
Gas Plasma ◽  
Weakly Ionized

Herein is described a calculation of the effective coffision frequency νeffof a low- density, shock-heated argon plasma under the influence of a weak electric field which oscillates harmonically with angular frequency ω. It is shown that, for the high frequency case ω >whereis the collision frequency in a Maxwellian gas plasma, one has νeff⋍ 2, provided that the imaginary part of the argon plasma conductivity is negligibly small in comparison to the real part. The influence of the theoretical model used to calculate νeffon the values of the electron temperatureTederived from measurements is compared with the results obtained in a data reduction for which the hard-sphere model for particle encounters was utilized.

Dither in a rolling airframe flight vehicle with a two-position actuator: An amplitude distribution approach

2016 ◽  
Vol 39 (8) ◽  
pp. 1205-1215 ◽  
Author(s):  
Bahram Mohammadi ◽  
Mohammad Reza Arvan ◽  
Yousof Koohmaskan
Keyword(s):  
High Frequency ◽  
Degrees Of Freedom ◽  
Coupling Effect ◽  
Cross Coupling ◽  
Amplitude Distribution ◽  
Feedback System ◽  
Flight Vehicle ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Minimal Error

Rolling airframe manoeuvring is a type of manoeuvre in which the missile provides continuous roll during flight. Cross-coupling between the angle of attack and sideslip in rolling airframe missiles (RAMs) yields a coning motion around the flight path. As the pitch and yaw cross-coupling effect decreases, the radius of this coning motion decreases and the accuracy of the control system increases. Two-position (on–off) actuators are used in most RAMs. The presence of a two-position actuator in a feedback system makes its characteristics non-linear. A high-frequency signal so-called dither is applied to compensate for the non-linearity effect of the actuator characteristic in the feedback system and to stabilize the coning motion. The amplitude distribution function (ADF) method in dither analysis shows that the smoothed non-linearity characteristic can be computed as the convolution of the original non-linearity and the ADF of the dither signal. According to the four-degrees-of-freedom (4-DOF) equations of RAMs in a non-rolling frame and regarding various dither signals through the ADF approach on a two-position actuator, an analytical condition for dither amplitude in coning motion stability of RAMs is derived. It was shown that the triangular signal with specified amplitude and high enough frequency led to a smoother response of two-position actuators. Finally, by applying beam-riding guidance to a RAM, the performance of dithers for decreasing the distance of the missile from the centre of the beam is validated through simulations. It is illustrated that applying the triangular dither resulted in minimal error.

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