Gun has thin metal foil disc which positions or localizes gas to be ionized during electrical discharge cycle, overcoming major limiting factor in obtaining such plasmas. Expanding plasma front travels at 190 km/sec, compared to plasmas of 50 to 60 km/sec previously achieved

Espy, P. N.

English

NASA Technical Reports Server

Oscilloscope 
Capacitor 
Bank
October 1971
	 Brief 71-10383 
NASA TECH BRIEF 
Marshall Space Flight Center 
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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. 
High Density Plasma Gun Generates Plasmas at 190 Kilometers Per Second 
High Voltage	 IOscilloscope 
Pulse Generator I F____1	 Delay Delay I 
Camera	 Camera 
II Pickup
 
Photo iode
C: 	 JLJ 
IPhotodiode 
Spark Gap
	
. 
Switch	 Vacuum Pump 
Center Connection	 Insulator	 Retaining Flange 
Shield Connection	 Conductive Foil 
Detail: Longitudinal Section of New Generator 
A plasma gun fitted with a thin metal-foil disc 
produces dense plasmas with extremely high velocities. 
The disc (of aluminum or lithium) positions or local-
izes the gas to be ionized during the electrical dis-
charge cycle, overcoming the major limiting factor 
iii obtaining such plasmas. 
The disc, which is positioned to form a shorting 
path between the two coaxial electrodes (see fig.), is 
cut a little oversize so that the periphery folds over 
the surface of the outer electrode. A 20,000 V capac-
itor bank with a capacitance of 45 to 80 mF ionizes
the disc and is discharged by a spark gap switch, 
which is triggered by a high voltage pulse. The 
niaximuni velocity of the plasma is obtained when 
the foil is positioned to yield an acceleration time 
which is exactly equal to the duration of the first 
quarter cycle of the capacitor bank. The accelera-
tion time is measured with respect to the exhaust 
end of the plasma gun. 
The trigger pulse also activates two cameras 
which sequentially photograph the plasma front 
traveling down the vacuum chamber. Two photo-
coil! irnied is crlciil) 
As 
lqw
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Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
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https://ntrs.nasa.gov/search.jsp?R=19710000381 2020-03-17T02:29:00+00:00Z
diode sensors detect the optical radiation from the 
plasma. Using the data on the elapsed time be-
tween the output of the sensors and on their physical 
separation, the velocity of the plasma can be cal-
culated. Data obtained from the the instrumentation 
setup indicates that the expanding plasma front 
travels at about 190 kni/sec, in comparison to 
plasmas of only 50 to 60 km/sec previously achieved. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Code A&TS-TU 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B71-10383
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Royalty-free non-exclusive 
licenses for its commercial use will be granted by 
NASA. Inquiries concerning license rights should 
be made to: 
Patent Counsel 
Mail Code A&TS-PAT 
George C. Marshall Space Flight Center 
Marshall Space Flight Center, Alabama 35812 
Source: P. N. Espy

Marshall Space Flight Center

(M FS-20589)
. 
. 
Brief 71-10383	 Category 03


High density plasma gun generates plasmas at 190 kilometers per second

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