In one method, fluorescent dye is deposited into tracks of radiograph and viewed under ultraviolet light. In second method, track-etch radiograph is placed between crossed polaroid filters, exposed to diffused light and resulting image is projected onto photographic film

Morley, J.

English

NASA Technical Reports Server

March 1973
	 B73-10027 
NASA TECH BRIEF 
S	 Lewis Research 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 
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. 
TWO NEW METHODS TO INCREASE THE CONTRAST

OF TRACK-ETCH NEUTRON RADIOGRAPHS 
FLUORESCENT DYE METHOD 
CAMERA 
FLUORESCING
ULTRAVIOLET 
LIGHT souPr'1 
TRACKS —F. 	 / 
\/	
I 
TRACK-ETCH NEUTRON RADIOGRAPH 
The Problem:	 The Solution: 
Track-etching is one of several methods used for 
recording neutron radiographs. This method consists of 
placing a piece of clear track recording material behind a 
converter screen located behind the subject exposed to a 
neutron beam. Neutrons passing through the subject and 
striking the converter screen cause ions to be emitted. 
These ions penetrate the clear track recorder material 
where they cause structural damage in their paths. The 
track recorder is then etched in a suitable reagent. The 
etching process selectively removes material from the 
damaged areas leaving pits or tracks. The arrangement of 
millions of these tracks in the recorder comprise the 
track-etch neutron radiograph. The track-etch method 
produces radiographs which are highly accurate but which 
are difficult to read because of poor contrast. Other 
systems are available but do not produce a sharp image 
5 and have poor contrast. 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Two new methods have been developed for increasing 
the contrast of track-etch neutron radiographs. In one 
method, a fluorescent dye is deposited into the tracks of 
the radiograph and viewed under ultraviolet light. In the 
other method, the track-etch radiograph is placed between 
crossed polaroid filters, exposed to diffused light and the 
resulting image projected onto photographic film. 
How It's Done: 
FLUORESCENT DYE METHOD 
The fluorescent dye technique used to enhance the 
contrast of track-etch neutron radiographs is shown in 
Figure 1. A fluorescent dye is sprayed onto the tracked 
side of the track-etch radiograph and allowed to partially 
dry. The surface of the radiograph is then wiped clean. 
The radiograph is placed on a flat dull black surface in a 
darkened room and illuminated with ultraviolet light 
(continued overleaf) 
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19730000027 2020-03-17T06:37:37+00:00Z
CROSSED POLAROID METHOD 
f 
LAMP	 DIFFUSING	 POLARIZING TRACK-ETCH	 ANALYZING	 VIEWER 
FILTER	 FILTER	 RADIOGRAPH	 FILTER 
directed onto it at 45° from normal incidence. The 450 
angle reduces the background interference caused by the 
blue and violet components of the ultraviolet light source. 
The dye trapped in the tracks absorbs the ultraviolet light 
and fluoresces. The tracked areas appear bright yellow, 
while the untracked areas appear essentially black. The 
fluorescing radiograph is then photographed from normal 
incidence. The optical density obtained by the fluorescent 
dye method is about 0.37. 
CROSSED POLAROID METHOD 
The crossed polaroid filter technique of enhancing the 
contrast of track-etch neutron radiographs is shown in 
Figure 2. The track-etch negative is placed between two 
light polarizing filters which have their polarizing axes 
oriented 90° from each other. Diffuse light is passed 
through the first filter (the polarizing filter), and polarized 
in one direction. The polarized light passes through the 
track-etch radiograph and then through the second filter 
(the analyzing filter). The portion of the polarized beam 
that passes through untracked areas of the radiograph is 
transmitted with its polarization unchanged, and filtered 
out by the analyzing filter. The portion of the polarized 
beam that strikes the tracked areas is scattered, the tracks 
in the radiograph serving as light scattering centers. The 
scattering process changes the polarization of that light so 
that a portion of it is polarized parallel to the optical axis 
of the analyzing filter. This portion of the beam is then 
transmitted onto the viewer. Since only that light which is 
scattered by the tracks is transmitted, only the track 
location information is transmitted to the viewer. The 
resulting image is viewed directly or projected onto
photographic film. Since the tracks are randomly 
oriented, a diffuse light source is used to increase the 
probability of scattering. The optical density obtained by 
using the cross polaroid method is about 2.4. 
Notes: 
1. The following documentation may be obtained from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.95) 
Reference: NASA TM-X-67947 (N72-12379), Two 
New Methods to Increase the Contrast of Track-
Etch Neutron Radiographs 
2. Technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B73-10027 
Patent Status: 
NASA has decided not to apply for a patent. 
Source: James Morley
Lewis Research Center
(LEW-1 1893) 
B73-10027	 Category 03


Two new methods to increase the contrast of track-etch neutron radiographs

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