Mikrowelleninterferometrie an elektromagnetisch erzeugten Stoßwellen

1965 ◽  
Vol 20 (7) ◽  
pp. 870-875
Author(s):  
W. Makios ◽  
H. Muntenbruch
Keyword(s):  
Shock Waves ◽  
Shock Front ◽  
Doppler Effect ◽  
Initial Pressure ◽  
Simple Construction ◽  
Velocity Measurements ◽  
T Tube ◽  
The Doppler Effect ◽  
Mach 10 ◽  
Made In

Velocity measurements of electron front in electromagnetically generated T-tube shock waves, have been made with 4 mm microwaves using the DOPPLER effect. The measurements were made in hvdrogen at an initial pressure of 1 to 5 torr. The shockfront velocity was between Mach 5 and Mach 20. It is shown that the reflection of microwaves occurs at the luminous front at low velocities, at the shock front at higher velocities. There is a region in between (at about Mach 10) where a reflection takes place at both fronts. For this case the electron density in the shock front can be determined within a factor of 2. For these investigations a microwave interferometer of simple construction was developed. This interferometer is fully described.

Interferometrische Untersuchungen an elektromagnetisch beschleunigten Stoßwellen

1965 ◽  
Vol 20 (2) ◽  
pp. 196-202 ◽  
Author(s):  
H. Brinkschulte ◽  
H. Muntenbruch
Keyword(s):  
Shock Waves ◽  
Shock Front ◽  
Discharge Plasma ◽  
Shock Velocity ◽  
Computational Method ◽  
Density Jump ◽  
Precursor Effects ◽  
Shock Fronts ◽  
Selection Of ◽  
Made In

The phenomena of shock waves generated electromagnetically in T-tubes were studied with a MACH-ZEHNDER interferometer. The measurements were made in hydrogen at initial pressures from 2.5 to 10 mm Hg. Shock velocity varied between Mach 6 and Mach 20. It was found that there are two fronts: the luminousity front due to the discharge plasma and the non-luminous shock front in front of this. The distance between the shock front and the luminousity front decreases with increasing velocity. At vs ⍙ Mach 20 the luminousity front reaches the shock front. Shock fronts are always plane. The density decreases directly behind the shock front. The shock waves thus formed cannot be described with the RANKINE-HUGONIOT equations. At small velocities, the density jump is 6, at higher velocities the gas is dissociated. The refractive index of atomic hydrogen can be measured. Simultaneously the selection of the computational method used to describe the shock conditions in hydrogen can be justified. Precursor effects have no influence, relaxations could not be seen.

Interferometrische Untersuchungen an elektromagnetisch beschleunigten Stoßwellen II

1967 ◽  
Vol 22 (4) ◽  
pp. 438-443
Author(s):  
H. Brinkschulte
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Shock Front ◽  
Time Dependence ◽  
Discharge Plasma ◽  
Initial Pressure ◽  
Homology Theory ◽  
Density Jump ◽  
Current Pulses ◽  
Steady Shock

The shock waves produced in T-tubes were investigated with a MACH-ZEHNDER interferometer. The experiments were conducted in hydrogen at an initial pressure of 5 torr. A power crowbar arrangement was used to produce single current pulses. These caused single shock waves to occur with every discharge. Reproducible, non-steady shock waves separated from the discharge plasma were observed at MACH numbers M < 15. By measuring the time dependence of the velocity of the shock front over the entire length of the tube (60 cm) it was found that the shock front behaves in accordance with the homology theory of v. WEIZSÄCKER. From the interferograms it is also possible to determine (but only qualitatively) the drop in density immediately behind the front. As the density jump increases, this drop becomes steeper and steeper—again in agreement with the theory. Moreover, it was shown by side-on photographs taken at various distances from the electrodes that the shock front becomes plane once the shock wave has covered a path ten times longer than the tube diameter.

scholarly journals Exploiting the Low Doppler Tolerance of Noise Radar to Perform Precise Velocity Measurements on a Short Set of Data

Signals ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 25-40
Author(s):  
Christoph Wasserzier
Keyword(s):  
Doppler Effect ◽  
Radar Data ◽  
Velocity Measurements ◽  
Illumination Time ◽  
Coherent Integration ◽  
Noise Radar ◽  
Highly Sensitive ◽  
Velocity Information ◽  
The Doppler Effect ◽  
A Current

The extraction of velocity information from radar data by means of the Doppler effect is the driving factor for the investigations presented in this paper. A method for the quantification of the Doppler tolerance in continuous emission (CE) noise radar is introduced, addressing a current lack in literature within the frame of CE noise radars. It is shown that noise radar is highly sensitive to the Doppler effect, an issue that often results in a low Doppler tolerance especially for long coherent integration intervals. In general, the Doppler sensitivity is considered as a drawback but, in this paper, along with the absence of range-Doppler coupling in noise radar, it is turned into an advantage allowing for a very precise Doppler estimation. This new signal processing approach for Doppler extraction is detailed and its feasibility is proven on the basis of experimental data. The presented method requires much less data, i.e., target illumination time, than conventional Doppler analyses and, therefore, is beneficial in terms of radar resource management.

scholarly journals On the application of interference methods to the study to the study of the origin of certain spectrum lines

1915 ◽  
Vol 91 (631) ◽  
pp. 421-431 ◽  
Keyword(s):  
Doppler Effect ◽  
Line Of Sight ◽  
Spectral Series ◽  
Definite Evidence ◽  
Great Progress ◽  
The Doppler Effect ◽  
Band Spectra ◽  
The Masses ◽  
Low Pressures ◽  
Made In

In recent years, great progress has been made in the study of the nature of spectra and of spectral series, but it may be said that very little is yet known as to the nature of the luminous particles from which different spectrum lines originate. It is generally supposed that band spectra are in some way due to molecules, whilst series spectra are usually associated with the atom. Enhanced lines were for many years supposed to be due to proto-elements, or simplified forms of the chemical atom, a view which has recently to some extent fallen into discredit. The evidence for all these hypotheses is of a circumstantial nature, and very little definite evidence as to the nature of the luminous particles is available. In their recent important researches, Buisson and Fabry have opened up a new method of attacking the problem. The method adopted by these investigators consists in measuring the limiting order of interference at which fringes can be observed for different radiations. The limiting order of interference depends on the widths of the spectrum lines, from which certain deductions may be made with regard to the temperature of the source of the radiations, and the masses of the particles which are concerned in their production. The theory of the method has recently been discussed by Lord Rayleigh and by Schönrock. The chief circumstance which need be considered as determining the widths of spectrum lines produced in gases at low pressures is the Doppler effect due to the motion of the luminous particles in the line of sight. The researches of Michelson have shown that at higher pressures a broadening of the lines occurs, this broadening being attributed to disturbances caused by collisions between the luminous particles, but that at pressures below one thousandth of an atmosphere this cause of broadening may be considered negligible.

Investigation of shock-wave deformation history from recovered structure

1986 ◽  
Vol 44 ◽  
pp. 434-435
Author(s):  
M.A. Mogilevsky ◽  
L.S. Bushnev
Keyword(s):  
Shock Wave ◽  
Plastic Deformation ◽  
Dislocation Density ◽  
Shock Waves ◽  
Shock Front ◽  
Single Crystals ◽  
Residual Deformation ◽  
Deformation Structure ◽  
Deformation History ◽  
Deformation Velocity

Single crystals of Al were loaded by 15 to 40 GPa shock waves at 77 K with a pulse duration of 1.0 to 0.5 μs and a residual deformation of ∼1%. The analysis of deformation structure peculiarities allows the deformation history to be re-established.After a 20 to 40 GPa loading the dislocation density in the recovered samples was about 1010 cm-2. By measuring the thickness of the 40 GPa shock front in Al, a plastic deformation velocity of 1.07 x 108 s-1 is obtained, from where the moving dislocation density at the front is 7 x 1010 cm-2. A very small part of dislocations moves during the whole time of compression, i.e. a total dislocation density at the front must be in excess of this value by one or two orders. Consequently, due to extremely high stresses, at the front there exists a very unstable structure which is rearranged later with a noticeable decrease in dislocation density.

ON THE THEORY OF THE DOPPLER EFFECT IN A MOVING MEDIUM

1998 ◽  
Vol 13 (01) ◽  
pp. 1-6 ◽  
Author(s):  
BRUNO BERTOTTI
Keyword(s):  
Solar Wind ◽  
Doppler Effect ◽  
Dispersive Medium ◽  
Time Derivative ◽  
Optical Path ◽  
Moving Medium ◽  
Perturbation Theorem ◽  
Hamiltonian Theory ◽  
The Doppler Effect ◽  
Definition Of

The increase in the accuracy of Doppler measurements in space requires a rigorous definition of the observed quantity when the propagation occurs in a moving, and possibly dispersive medium, like the solar wind. This is usually done in two divergent ways: in the phase viewpoint it is the time derivative of the correction to the optical path; in the ray viewpoint the signal is obtained form the deflection produced in the ray. They can be reconciled by using the time derivative of the optical path in the Lagrangian sense, i.e. differentiating from ray to ray. To rigorously derive this result an understanding, through relativistic Hamiltonian theory, of the delicate interplay between rays and phase is required; a general perturbation theorem which generalizes the concept of the Doppler effect as a Lagrangian derivative is proved. Relativistic retardation corrections O(v) are obtained, well within the expected sensitivity of Doppler experiments near solar conjunction.

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