A cesium iodide crystal is fused to the lithium fluoride faceplate of a photon scintillator image tube. The conventional silver chloride solder is then used to attach the faceplate to the metal support

Fleck, H. G.

English

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NASA TECH BRIEF is
May 1964	 Brief 63-10476 
This NASA Tech Brief is issued by the Technology Utilization Division to acquaint industry 
with the 'technical content of an innovation derived from the NASA space program. 
Cesium Iodide Crystals Fused to Vacuum Tube Faceplates 
Silver Chloride So 
Glass Envelope 
The problem: Attaching a thin crystal of thallium-
activated cesium iodide phosphor to a spun metal 
support in a photon scintillator image tube. Attempts 
to attach the crystal directly to the metal support 
with silver chloride solder were unsuccessful because 
interaction of the melted solder destroyed the struc-
ture and scintillation characteristics of the crystal. 
The solution: Fusing the cesium iodide crystal to a 
lithium fluoride faceplate and using the conventional 
silver chloride solder to attach the faceplate to the 
metal support. 
How it's done: The cesium iodide crystal (m.p.= 
621 *C) is positioned on a polished lithium fluoride 
faceplate (m.p.=870°C) and the two are heated under 
close temperature control in an inert atmosphere until 
a thin layer of the cesium iodide crystal melts and wets 
the contact face of the lithium fluoride crystal. The 
two crystals are then cooled to room temperature at a 
slow rate to assure a strong strain-free junction. To 
complete the process, silver chloride is used to solder 
the lithium fluoride faceplate to the metal support. 
Temperature cycling of the crystal assembly pre-
sents no difficulties because the thermal expansion 
coefficients of the two crystals are closely matched.
rn Fluoride Faceplate 
Notes: 
1. By this method very thin scintillation crystals can 
be mounted on a transparent faceplate that is 
sufficiently stiff to resist flexing and consequent 
destruction of the vacuum seal. 
2. This method may also be used to fuse a cesium 
iodide crystal of very thin cross section to a glass 
faceplate. 
3. For further information about this innovation, 
inquiries may be directed to: 
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland 20771 
Reference: B63-10476 
Patent status: NASA encourages the immediate 
commercial use of this invention. It is owned by 
NASA and inquiries about obtaining royalty-free 
rights for its commercial use may be made to NASA 
Headquarters, Washington, D.C. 20546. 
Source: Electro-M echanical Research Inc.
under contract to
Goddard Space Flight Center
(GSFC-67) 
This document was prepared under the sponsorship of the National 	 this document, or that the use of any information, apparatus, method. 
Aeronautics and Space Administration. Neither the United States Govern ,	 or process disclosed in this document may not infringe privately-owned 
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes	 rights: or B. Assumes any liabilities with respect to the use of, or for 
any warranty or representation, express or implied, with respect to the	 damages resulting from the use of, any information, apparatus, method, 
accuracy, completeness, or usefulness of the information contained in	 or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19630000081 2020-03-11T16:47:30+00:00Z


Cesium iodide crystals fused to vacuum tube faceplates

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