Method provides optimization of dimensions in vented RF components for predictable performance at critical pressures, eliminates leakage from hermetically sealed types, and utilizes coaxial RF multicouplers

Rainwater, L. L.

English

NASA Technical Reports Server

July 1972
	 B72-10316 
NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announce new . technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Properties of Ionization Breakdown of

Air at Microwave Frequencies and

Optimization of Component Dimensions for

Maximum Microwave Power 
	
The analytical approach to the determination of 	 potential energy of the gas. The kinetic energy is 
	
ionization breakdown fields in gases at microwave 	 acquired by acceleration of the electron in the rf field. 
	
frequencies is the solution of a differential equation 	 A gas discharge occurs when the electron density 
	
developed for particular gases from Boltzmann's ionized 	 from the ionization of the gas becomes equal to the loss 
	
gas equation. This approach has been successful for	 of electrons by diffusion, recombination, and attach-
	
hydrogen, helium, neon, argon, and mixtures of these
	 ment. 
gases. Analytical treatment of air, oxygen, nitrogen, 
krypton, and xenon has not been successful primarily 
because a simple analytic formulation for the collision 
frequency has not been found which can be used in 
Boltzmann's equation. However, the accumulation of 
experimental data and the development of phenom-
enological theory for the utilization of the experimental 
data have provided reasonably accurate ionization break-
down predictions for the latter gases, especially air. 
Recently, considerable interest has developed for the 
use of vented rf components because of the difficulties 
and uncertainties that are associated with leakage from 
the hermetically sealed types. 
Leakage from hermetically sealed types is unpredict-
able, and rf breakdown will occur when the pressure 
drops to critical value, provided that the rf fields within 
the component are above threshold breakdown limits. 
They usually are above threshold breakdown, because 
greater power handling capability is the primary reason 
for sealing the components. 
Microwave breakdown occurs in gas when the rf field 
imparts sufficient kinetic energy to a sufficient number 
of electrons for ionization due to the collision of the 
electrons with gas molecules. The kinetic energy of the 
electrons must be equal to or greater than the ionization
Category 01 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights. 
Design techniques have been formulated for vented 
rf components, which eliminate the leakage problem at 
the expense of restricted rf bandwidth and rf power 
handling capabilities, and which permit the use of such 
vented components through the critical pressure region 
without corona breakdown. The method provides opti-
mization of dimensions in rf components for predictable 
performance at critical pressures in the vented con-
figuration. Special emphasis was given to coaxial if 
multicouplers. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A&TS-TU 
Huntsville, Alabama 35812 
Reference: B72-10316 
Patent status: 
No patent action is contemplated by NASA. 
Source: L. L. Rainwater of

Sperry Rand Corporation

under contract to

Marshall Space Flight Center 
(MFS-2 1924)
https://ntrs.nasa.gov/search.jsp?R=19720000315 2020-03-17T03:29:29+00:00Z


Properties of ionization breakdown of air at microwave frequencies and optimization of component dimensions for maximum microwave power

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