Detector includes delay lines connected to each detector surface strip. When several particles strike different strips simultaneously, pulses generated by each strip are time delayed by certain intervals. Delay time for each strip is known. By observing time delay in pulse, it is possible to locate strip that is struck by particle

Auer, S. O.

English

NASA Technical Reports Server

NASA TECH BRIEF 
Goddard Space Flight Center .
December 1974
	 B74-10230 
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 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Particle Impact Location Detector 
High-energy microscopic particles are studied with 
the aid of particle detectors. One of these detectors, 
described in NASA Tech Brief 73 . 10282 (GSC-1 1291), 
is used to determine the locations of particles striking 
its surface. When particles strike it surface, some have 
sufficient energy to penetrate it and emerge as ejecta 
continuing downstream. 
The flight paths of these ejecta can be determined 
using a similar detector. The detector has to be modified 
because ejecta come in larger numbers than the original 
particles, often striking its surface simultaneously. Un-
fortunately none of the existing detectors is capable of 
locating several particle impacts at the same time. 
Instead an imaginary impact point is indicated, con-
cealing the actual impact sites. 
A newly-designed particle detector includes delay 
lines connected to each detector surface strip. When 
several particles strike different strips simultaneously, 
the pulses generated by each strip are time delayed by 
certain intervals. The delay time for each strip is known. 
Therefore, by observing the time delay in a pulse, it is 
possible to locate the strip that is struck by a particle. 
.
Mesh
PARTICLE 
DETECTOR
Operational 
Delay	 Amplifier 
Line 
hM UM	 Processing 
Mesh Strips
Film 
Strips	 Mesh 
Distance Between 
Detectors 
(Divisor)
	
	 Film 
Strips 
Mesh 
S	 Strips 
DIFlop
EJECTA 
DETECTOR
 
Particle Detector System 
Digital-to-
Analog 
Converter 
Quotient 
Cubed and 
Multiplied 
by Constant 
To Analog 
Dividers 
I
J
(continued overleaf) 
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.
https://ntrs.nasa.gov/search.jsp?R=19740000230 2020-03-17T13:54:42+00:00Z
The detector as shown in the illustration is located on 
the common axis behind the particle detector. It 
includes three electrodes: the first one is a negatively 
biased mesh, the second consists of positively-biased 
mesh strips, and the third is an array of negatively-
biased metal film strips. The last two are connected to 
the delay lines and detect the negatively and positively 
charged particles, respectively. Negative particles are 
recorded as positive pulses and vice versa. 
Both delay lines are capacitively coupled and share a 
common output to a processing network. The output is 
terminated by a resistor which has the same characteristic 
impedance as the delay lines. This prevents undesirable 
pulse reflections. The opposite end of the other delay 
line is shorted to ground. Negative pulses feeding into it 
from the film strip electrode are reversed in polarity. 
Both the positive and negative pulses are fed through 
a high-input-impedance operational amplifier to the 
processing network. The processing network determines 
the respective delay times of the arriving pulses to 
indicate which strip was struck by a particle. 
A separate circuit is used to determine mass and 
velocity of the ejected particles. When a particle 
strikes the central electrode of the first detector, the 
resulting pulse sets the flip-flop in a binary one state 
while the ejecta are propagating to the second detector. 
After the ejecta reach the film strip terminal of the 
second detector, another pulse resets the flip-flop. In 
the interim when the ejecta are moving between the 
two detectors, the AND gate produces output in 
response to the clock pulses from an oscillator. Pulses
from the AND gate are fed to a digital-to-analog 
converter. The resulting output is a dc analog signal 
having a magnitude directly proportional to the travel 
time between the electrodes. This time is divided by the 
magnitude of the distance to provide velocity informa-
tion. The result is then cubed and multiplied by a 
constant and is applied to an analog divider to determine 
the mass of the particle. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Goddard Space Flight Center 
Code 207.1 
Greenbelt, Maryland 20771 
Reference: TSP74-10230 
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Inquiries concerning non-
exclusive or exclusive license for its commercial develop-
ment should be addressed to: 
Patent Counsel 
Goddard Space Flight Center 
Code 204 
Greenbelt, Maryland 20771 
Source: Siegfried 0. Auer

Goddard Space Flight Center

(GSC-1 1829)
[I 
. 
. 
B74-10230	 Category 03, 02


Particle impact location detector

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