Development of a New Plasma Diagnostic Technique Using Slow Positrons

1971 ◽  
Vol 42 (12) ◽  
pp. 4799-4807
Author(s):  
Gunter H. Lohnert ◽  
Richard T. Schneider
1975 ◽  
Vol 14 (3) ◽  
pp. 373-387 ◽  
Author(s):  
J. J. B. Frommelt ◽  
Ieuan R. Jones

A theoretical and experimental investigation of the forced radial magnetoacoustic oscillations of a magnetized plasma column is presented in this paper. Forced magneto-acoustic oscillations of a magnetized argon afterglow plasma are generated continuously by passing an RF current through a solenoid wrapped around the discharge tube. The radial variation of the amplitude of the magnetic field disturbance [bz(r)] associated with these oscillations is measured at various times during the decay of the afterglow plasma. A theoretical description of these oscillations is developed in which the collision frequencies between the various plasma constituents are treated as free parameters. The values of these free parameters at any given instant during the decay of the plasma are determined by fitting computed bz{r) radial profiles to the measured ones. The electron temperature Te, and the ion-neutral cross section for momentum transfer QD are deduced from these collision frequencies. The reliability of this plasma diagnostic technique is demonstrated by its ability to yield values for Te and QD which compare favourably with the results obtained by other workers.


2001 ◽  
Vol 16 (6) ◽  
pp. 863-874
Author(s):  
Jaroslav Pavlik ◽  
Petr Spatenka ◽  
Zdenek Stryhal ◽  
Vera Hrachova ◽  
Adolf Kanka ◽  
...  

1969 ◽  
Vol 11 (7) ◽  
pp. 611-613 ◽  
Author(s):  
A P Saxena ◽  
S C Gaur

1999 ◽  
Vol 135 (1) ◽  
pp. 171-185 ◽  
Author(s):  
E. Landi ◽  
G. Del Zanna ◽  
E. R. Breeveld ◽  
M. Landini ◽  
B. J.I. Bromage ◽  
...  

1982 ◽  
Vol 28 (2) ◽  
pp. 325-333 ◽  
Author(s):  
M. H. Brennan ◽  
A. L. McCarthy ◽  
M. L. Sawley

Magneto-acoustic oscillations were excited in a non-uniform, current-carrying plasma column. Measurements of the oscillating axial magnetic flux at a number of excitation frequencies were used to determine the equilibrium plasma properties. In agreement with previous theoretical studies, the radial profile of the plasma density is shown to be accurately determined, while it is not possible to obtain detailed information on the radial profile of the equilibrium magnetic field.


2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
Yoshito Sonoda ◽  
Yoichi Nakazono

The optophone with no diaphragm, which can detect sound waves without disturbing flow of air and sound field, is presented as a novel sound measurement technique and the present status of development is reviewed in this paper. The method is principally based on the Fourier optics and the sound signal is obtained by detecting ultrasmall diffraction light generated from phase modulation by sounds. The principle and theory, which have been originally developed as a plasma diagnostic technique to measure electron density fluctuations in the nuclear fusion research, are briefly introduced. Based on the theoretical analysis, property and merits as a wave-optical sound detection are presented, and the fundamental experiments and results obtained so far are reviewed. It is shown that sounds from about 100 Hz to 100 kHz can be simultaneously detected by a visible laser beam, and the method is very useful to sound measurement in aeroacoustics. Finally, present main problems of the optophone for practical uses in sound and/or noise measurements and the image of technology expected in the future are shortly shown.


2011 ◽  
Vol 20 (6) ◽  
pp. 065005 ◽  
Author(s):  
Jin-Young Bang ◽  
Kyoung Yoo ◽  
Dong-Hwan Kim ◽  
Chin-Wook Chung

1988 ◽  
Vol 117 ◽  
Author(s):  
Stephen W. Downey ◽  
Annette Mitchell ◽  
Richard A. Gottscho

AbstractAn obstacle to better design and control of plasma processes is our limited ability to monitor surface properties in situ. We describe a new plasma diagnostic technique, photoemission optogalvanic spectroscopy, which can be used to monitor surface contamination, etching rates, and end points. The experiment consists of irradiating a surface with a pulsed excimer or dye laser whose photon energy is above the substrate work function. Photoemission of electrons from the surface is detected by monitoring changes in the discharge current (optogalvanic effect). The technique is characterized by measuring signal strengths as a function of laser intensity, laser wavelength, and bias voltage in vacuum and in an Ar plasma. The technique is used to monitor contamination and etching end points in F-containing plasmas.


Author(s):  
J.A. Maksem ◽  
C. VanDyke ◽  
H.W. Carter ◽  
C.F. Galang

In the last decade fine needle aspiraration biopsy has gained recognition as a valuable diagnostic technique, and its benefits have been demonstrated in large series of patients with almost every type of tumor (1,2). The usual way to collect cellular material from needle-aspiration biopsies is to discharge the needle and syringe contents onto a microscopic slide and smear the material with another slide. The entire specimen is contained on the slides prepared at the time of biopsy. Serious technical difficulties are inherent to this method. 1) Inconsistent fixation, 2) drying artifact, 3) loss of tissue fragments, 4) inability to confirm impressions by a “second method”, and 5) retention of significant diagnostic material in the needle hub. Our technique avoids these difficulties.


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