Vacuum-type neutron image intensifier tube improves image detection in thermal neutron radiographic inspection. This system converts images to an electron image, and with electron acceleration and demagnification between the input target and output screen, produces a bright image viewed through a closed circuit television system

Berger, H.

Kraska, I.

Niklas, W.

Schmidt, A.

English

NASA Technical Reports Server

August 1967
	 Brief 67-10296 
tUY
 Ce.,
AEC-NASA TECH BRIEF 
AEC-NASA Tech Briefs describe innovations resulting from the research and development program 
of the U.S. AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial 
application. Tech Briefs are published by NASA and may be purchased, at 15 cents each, from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Thermal Neutron Image Intensifier Tube Provides 
Brightly Visible Radiographic Pattern 
Neutron 
Scintillator 
Input Target	 Photoemissive 
\	 - Layer
Amplified 
Neutron	 .—'''Visible 
Image	 Image 
Output 
k
	 Phospor 
Vacuum 
Envelope 
The problem: 
To improve current methods of image detection in 
thermal neutron radiographic inspection. Neutron 
radiography provides meaningful images of material 
combinations, which are not easily radiographed by 
conventional techniques; it provides another method 
for nondestructive testing. Sufficient image intensifi-
cation must be obtained so that it is feasible to use 
commercially available nonreactor neutron sources. 
Brightness must also be of sufficient intensity to 
enable fluoroscopic viewing of image without dark 
adaptation. A system for observing motion in the 
neutron radiographic image area is also needed. 
The solution: 
A vacuum-type neutron image intensifier tube 
consists of an input target (a combination of a neutron 
scintillator and photoemissive layer) and an output 
phosphor screen. The incoming image is converted to 
an electron image. A high voltage acceleration of the 
imitnin electrons, to gether with demagnification
between the input target and the output screen, con- 
tributes to the production of an intensified bright 
visible image. 
How it's done: 
An evacuated glass envelope was constructed with 
an input phosphor screen, 22 cm in diameter. The 
input target (approximately 0.4 mm thick) consists 
of a neutron scintillator and a photoemissfve layer. 
This scintillator is a powder mixture of lithium fluoride 
and ZnS (Ag) in a weight ratio ot' 1:4. To provide this 
powder mixture with a high neutron cross-section for 
a prompt neutron-alpha reaction, LiF is 95.72% en- 
riched with Li-6. Absorption of a neutron by the 
scintillator results in the emission of an alpha particle. 
As a result, the ZnS (Ag) phosphor is stimulated to 
emit light. The light causes the emission of electrons 
from the adjacent photoemissive layer. The electrons 
emitted from the photoemissive layer are maintained 
in an image sense and accelerated toward the phos- 
phor output screen by a voltage of about 30 kv. This 
.... — - . - o - - - - -	
-	 (continued overleaf) 
This document was prepared under the sponsorship of the Atomic 
Energy Commission and/or the National Aeronautics and Space 
Administration. Neither the United States Government nor any per-
son acting on behalf of the United States Government assumes any
liability resulting from the use of the information contained in this 
document, or warrants that the use of any information, apparatus, 
method, or process disclosed in this document may not infringe pri-
vately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19670000296 2020-03-11T20:36:19+00:00Z
produces a bright visible image of the incident neutron 
pattern. 
The neutron image obtained at the intensifier tube 
output is observed by means of a 525-line, 30-frame/ 
sec, interlaced, closed circuit television system. A 
vidicon system can be used for neutron intensities as 
low as 2 x 104
 n/cm 2 sec. 
Notes: 
1. Initial experimentation was conducted at 
Argonne's Juggernaut reactor facility and involved 
the use of a vidicon closed circuit television sys-
tem. Object spacing resolution was observed to be 
approximately 0.5 mm. Movements as fast as 5m/ 
min could be followed without blur. Imaging thick-
ness changes as small as 4% could also be observed 
in materials such as steel and uranium. In addition, 
it was found that radiographic inspection of radio-
active material was practically unaffected by 
gamma radiation levels of 4000 R/hr with the 
available neutron intensity (2 x 10 7
 n/cm 2
 sec). 
. The above television system makes it possible to 
conduct motion investigations using thermal 
neutrons. For example, the thermal expansion of 
nuclear reactor fuel and the flow of water in metal 
pipes are now being studied. Casting of high dens-
ity materials has been suggested as a future appli-
cation. 
1. Three tubes have been made and tested. The best 
tube provides a light yield of about 50 ft -lamberts 
at 107
 n/cm 2
 sec, a high contrast resolution of 
0.35 mm, and improved neutron-gamma response 
(about a factor of two better than shown in Note I). 
Further improvements in this latter factor and in 
resolution capability are now being sought in 
tubes under development.
4. Additional details are contained in IEEE Transac-
tions on Nuclear Science, April 1966, p. 79-83. 
5. Inquiries concerning this innovation may be di-
rected to:
Office of Industrial Cooperation 
Argonne National laboratory 
9700 South Cass Avenue 
Argonne, Illinois 60439 
Reference: B67-10296 
Source: H. Berger and I. Kraska

Metallurgy Division, Argonne National Laboratory

and W. Niklas and A. Schmidt

The Rauland Corporation

(ARG- 120) 
Patent status: 
Inquiries about obtaining rights for commercial 
use of this innovation may be made to: 
Mr. George H. Lee, Chief 
Chicago Patent Group 
U.S. Atomic Energy Commission 
Chicago Operations Office 
9800 South Cass Avenue 
Argonne, Illinois 60439 
Brief 67-10296	 Category 02


Thermal neutron image intensifier tube provides brightly visible radiographic pattern

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server