Vacuum container of radiation image multiplier tube and method of manufacturing the same

A vacuum container of a radiation image multiplier tube is disclosed, which is provided with a radiation input window made of Al or an Al alloy and an output portion made of a glass or ceramic insulator for outputting radiation image multiplied signals. Between the input window and the output portion is interposed a ring made of Fe or an Fe alloy, and an airtight joint between the ring of the input window is effected by hot pressure-bonding through a thin layer of Ni, Cu or Al. A method of manufacturing the vacuum container by means of such hot pressure-bonding is also disclosed.

The present invention relates to a radiation image multiplier tube such as 
an X-ray fluorescence multiplier tube for multiplying and reproducing 
images of a specimen to be tested by utilizing X-rays, .gamma.-rays or 
other equivalent radiation, particularly to the structure of a vacuum 
container thereof, and to a method of manufacturing the same. 
In X-ray fluorescence multiplier tubes, for example, attempts have been 
made to form the X-ray input window constituting a portion of the vacuum 
container from Al (aluminum) or an Al alloy (hereinafter referred to as 
"Al material") which is comparatively high in mechanical strength, 
superior in X-ray permeability and low in X-ray scattering, in place of 
glass which causes problems with X-ray scattering, decreases the quality 
of the image and so on. The output portion of the vacuum container should 
be composed of glass or a ceramic insulator in order to prevent an 
accelerating electrode from discharging to the outside and to guide the 
image multiplied signals such as visible rays or electrical signals 
converted in the inside of the tube to the outside. As is well known, it 
is not easy to effect a direct airtight joint either between glass and an 
Al material or between ceramic and an Al material, and a technique for a 
stable airtight joint between these materials providing in radiation image 
multiplier tubes having a relatively wide diameter has not been completed 
yet. Thus, it is practically desirable to provide an airtight joint at the 
Al material through an intermediate cylinder made of Fe or an Fe alloy 
such as an Fe-Ni-Co alloy known as "Kovar", which are capable of forming a 
stable airtight joint with glass and ceramic. It is a question of how to 
form the airtight joint between the Al material and the Fe or Fe alloy 
(hereinafter referred to as "Fe material") in this construction. U.S. Pat. 
No. 4,153,854 discloses a technique for effecting the airtight joint 
between the Al material and the Fe material in the vacuum container, by 
interposing a thin layer of Ag or of Ni and Ag therebetween by means of 
metal plating or deposition procedures and then forming a diffusion 
junction by applying heat and pressure thereto. Japanese Laid-open Patent 
application No. 138,861/1977 discloses a technique which involves plating 
Sn and Cu or Au between the Al material and the Fe material and forming an 
eutectic junction. Japanese Utility Model Publication No. 25,810/1974 
discloses a technique which involves forming Ni plated layers on the 
surfaces of both of the materials or effecting arc welding through a thin 
Ni layer therebetween. Although the known techniques of forming a 
diffusion junction or eutectic junction are effective solutions, they are 
inexpedient for industrial mass production because of the high price of 
raw materials and require improvements with respect to mechanical joint 
strength. The procedures based on welding and the diffusion junction 
present problems in that they cannot provide sufficient joint strength 
where diffusion between different metals is insufficient, and a brittle 
intermetallic compound is likely to be formed when the degree of diffusion 
is excessive, so these procedures are not widely adopted. 
The present invention was made under circumstances as hereinabove set 
forth, and the object of the present invention is to provide a radiation 
image multiplier tube vacuum container having an airtight junction which 
is extremely stable, has sufficient strength, and is formed by applying 
heat and pressure to one or more plated or deposited layers of Ni, Cu or 
Al, interposed between Al and Fe materials, and which is relatively 
suitable for mass production; and to provide a method of manufacturing the 
vacuum container in an easier and more stable manner. 
The present invention provides a vacuum container for a radiation image 
multiplier tube comprising a cylindrical body, a radiation input window of 
Al or an Al alloy provided at one end of the body and a glass or ceramic 
insulator member provided at the other end of the body with a portion 
thereof being employed as an output portion for outputting radiation image 
multiplied signals; characterized in that a first ring made of Fe or an Fe 
alloy constituting a portion of the cylindrical body is airtightly 
connected between the radiation input window and the insulator member with 
or without the interposition of a second ring made of Al or an Al alloy, 
and an airtight junction between the first ring and the input window or 
the second ring is formed by hot pressure-bonding with one or more thin 
layers of a metal selected from the group consisting of Ni, Cu and Al 
interposed therebetween. 
The present invention also provides a method of manufacturing a vacuum 
container for a radiation image multiplier tube in which Al or an Al alloy 
member constituting a radiation input window is airtightly joined to a 
glass or ceramic insulator member constituting an output portion for 
outputting radiation image multiplied signals through a first ring made of 
Fe or an Fe alloy, characterized in that, in bonding the first ring with 
the member of Al or Al alloy, one or more thin layers of a metal selected 
from the group consisting of Ni, Cu and Al are previously formed by metal 
plating or deposition on a portion to be joined of the member of Al or Al 
alloy and/or a portion to be joined of the first ring, are superposed in 
planes perpendicular to the axis of the tube and are airtightly joined by 
hot pressure-bonding while applying pressure in the direction of the tube 
axis by means of a press apparatus.

The X-ray image intensifier tubes will be described by way of examples with 
reference to the drawings, in which the same parts are indicated by the 
same reference numerals. 
The embodiments shown in FIGS. 1 to 4 have the following constructions. An 
X-ray fluorescence multiplier tube 21, as shown in FIG. 1, is accommodated 
in a camera lens mounting table 23 lined with a magnetic shield cylinder 
22 and a lead plate 23a. A vacuum container comprises an X-ray input 
window 24, a body portion 25 composed of a glass cylinder with a bottom as 
a main part, and an output portion 26. Inside the container are disposed 
an input base plate 28 having an X-ray excited fluorescent layer and a 
photoelectric cathode surface 27, a grid 29, an anode 30 and an output 
fluorescent plate 31 in a predetermined positional relation in the order 
named from the top of FIG. 1. The input window 24 of the vacuum container 
is 0.5 to 2.0 mm thick and is composed of aluminum (Al) or an Al alloy 
(hereinafter referred to as "Al material") containing at least one of Si, 
Cu, Mn and Mg in an amount of about 0.5% or higher to increase the 
strength. The input window 24 may have a convex structure, being 
spherically curved toward the outside. Alternatively, it may be flat for a 
small and compact tube. The input window 24 has a peripheral portion 41 
which lies in a plane perpendicular to the axis of the tube, and the 
peripheral portion 41 is joined airtightly to a intermediate metal ring 42 
having a half section in the form of a crank by procedures as will be set 
forth hereinafter. A sealing ring 43 comprising a Kovar cylinder is 
airtightly welded to an open end portion 25b of a glass cylinder insulator 
25a of the body portion 25, and the open end portion is provided with a 
flange 43b and a cylinder portion 43a capable of fitting with a cylinder 
portion 42a and the outer circumference of a flange 42b. In the assembly 
of the tube, the intermediate metal ring 42 joined airtightly and 
integrally to the outer periphery of the input window 24 is engaged with 
the sealing ring 43 made of Kovar which is joined integrally to the body 
25 after the deposition of each of the electrodes. The end portions of the 
flanges 42b and 43b are airtightly welded over their peripheries with 
local heating by inert gas arc welding or the like. The sealed portion is 
indicated by reference numeral 44, and the welded portion is also utilized 
for fixing the tube 21 to the outer magnetic shield material 22. For the 
intermediate metal ring 42, a material easily weldable with the Kovar 
sealing ring 43, such as Fe, or an Fe alloy (hereinafter referred to as 
"Fe material"), e.g., Fe--Ni--Cr (stainless steel), Fe--Ni--Cu alloy 
(ferromagnetic materials such as Permalloy and the like) or Fe--Ni--Co 
alloy (Kovar), is employed, and a thickness of 0.5 to 2.0 mm is 
appropriate. 
The formation of the airtight junction between the input window 24 of the 
Al material and the intermediate metal ring 42 of the Fe material will be 
explained by preferred manufacturing methods. The intermediate metal ring 
42 is covered with a Ni plated layer 45 (see FIG. 2). The Ni plated layer 
may have a thickness of 100 .mu. or less and, preferably, 10 to 50 .mu.. 
As shown in FIGS. 3 and 4, sufficiently degreased and washed parts are 
disposed between a pair of lower and upper press apparatuses 48 and 49, 
respectively, containing heating heaters 46 and 47. The parts comprise a 
flat portion 42c of the intermediate metal ring 42 having the Ni plated 
layer, the peripheral portion 41 of the input window, and a washer ring 50 
composed of a metal material such as an Fe material or a Ni material 
having a softening temperature higher than that of the Al material of the 
input window and having a thickness of 0.2 to 1.0 mm. These parts are 
superposed in the order named from the bottom as shown in the drawing. The 
parts are arranged in contact with each other in planes perpendicular to 
the axis of the tube. Ring tip portions 48a and 49a of the respective 
press apparatuses 48 and 49 are selected so as to equal in width to 
airtight junction, or slightly wider than the width of the lower side 48a. 
In this embodiment, the width of the tip portion 49a of the upper press 
apparatus is wider than that of the washer ring 50. The temperature is 
raised by applying heat to each of the press apparatuses through power 
sources 51 and 52. The press apparatuses are formed with a material having 
a superior hardness and heat resistance such as, for example, an Fe alloy. 
The temperatures of the tip portions 48a and 49a are raised so as to 
maintain a temperature of about 470.degree. C. at the metals to be joined. 
This is accomplished by raising the temperature of the lower side 48a in 
contact with the intermediate metal ring 42, as in the drawing, to about 
580.degree. C., for example, relative to the upper side 49a at about 
500.degree. C. in contact with the Al material of the input window through 
the washer ring 50. The difference in temperatures can prevent overheating 
of the input window and subsequent deformation. At the same time, pressure 
is applied to the press apparatuses from the top and the bottom as shown 
by arrows (F), and the pressure is maintained for several minutes or more. 
Although the pressure (F) is controlled depending upon the temperature of 
the junction, it is desired to apply pressures of 1,000 kg/cm.sup.2 at 
470.degree. C. 
The procedures as mentioned hereinabove allow the intermediate metal ring 
42 of the Fe material to be joined by heating and pressure to the input 
window of the Al material through the thin Ni layer 45, thereby providing 
an airtight junction. The section of the junction is shown in FIG. 4. It 
is to be noted that, in a range in which the tip portions 48a and 49a of 
the lower and upper press apparatuses, respectively, apply pressure, as 
indicated by the dashed line, the Al material of the input window 24 is 
compressed into a thin layer and strongly joined by pressure welding to 
the intermediate metal ring 42. The washer ring 50 also becomes attached 
to the Al material of the input window, although without airtightness. In 
this case, the washer ring 50 is not attached at all to the upper press 
apparatus 49a. Thus, the washer ring 50 assists the hot pressure-bonding 
of the Al material of the input window with the intermediate metal ring in 
an airtight manner, and serves to prevent attachement of the Al material 
to the press apparatus while controlling deformation because it reinforces 
the peripheral portion of the input window. Accordingly, the washer ring 
may be mounted as it is to a tube product or may be joined to the input 
window and the intermediate metal ring if it can be removed without damage 
to the airtight junction between them. In the latter case, the washer ring 
is removed after joining. As the washer ring has the functions as 
hereinabove set forth, it is preferably composed of a material that has a 
hardness similar to that of the material for the intermediate metal ring 
42 or the press apparatus. 
FIG. 5 illustrates the results of analysis by means of an X-ray 
microanalyzer of the metal element profile of the sectional portion bonded 
by means of heat and pressure as mentioned hereinabove. In this figure, 
the abscissa in the characteristic pattern indicates the position along 
the line X.sub.1 --X.sub.2 of the hot pressure bonded portion, and the 
ordinate indicates the measurement value. It was seen that the Fe, Ni and 
Al did not diffuse deeply within the other metal because the boundaries 
between them were relatively clear. Accordingly, the result indicates that 
there is not risk of forming brittle intermetallic compounds in a thick 
layer, and there is a physically and mechanically stable situation of 
welding by heating and pressure. 
According to the embodiment mentioned hereinabove, the thin Ni layer 45 may 
be formed over the whole surface of the intermediate metal ring 42 so that 
it is easy to sufficiently control its thickness and adhesion strength. 
The airtight welding of the sealed portion at the position indicated by 
the reference numeral 44 may be effected in a sure and easy manner without 
any further processing so that it is extremely effective for industrial 
application, particularly in combination with the low price of materials 
to be employed for the metal plated layer. This facilitates the 
manufacture of the vacuum container because a thin metal layer is not 
necessarily formed on the input window composed of a relatively thin Al 
material. Furthermore, the vacuum container in accordance with the present 
invention is easy to handle because the input window is previously 
integrally joined to the intermediate metal ring. Thereafter, the 
radiation-excited fluorescent layer and the photoelectric cathode layer 
may be formed directly on the inner surface of the input window so that it 
is applicable to a construction in which the input base plate 28 as shown 
in FIG. 1 is omitted. 
FIG. 6 illustrates an embodiment in which the width (W.sub.1) in the radial 
direction of the washer ring 50 is smaller than the width (W.sub.2) of the 
tip portion 49a of the upper press apparatus 49 mounted in contact 
therewith. This enables the range of the airtight junction between the 
input window 24 and the intermediate metal ring 42 to be equal to the 
width (W.sub.1) of the washer ring 50. Thus, the width of the airtight 
junction may be controlled arbitrarily by choosing a desired width 
(W.sub.1) of the washer ring 50. 
FIG. 7 illustrates an embodiment in which the thin Ni plated layers 51 and 
52, respectively, are formed on both surfaces of the peripheral portion 41 
of the input window 24 and over the whole surface of the washer ring 50. 
The thin Ni plated thin layer 51 to be formed on the peripheral portion of 
the input window 24 is formed outside the effective input surface in order 
not to cause attenuation of the incident X-rays. The quality of hot 
pressure-bonding will be rendered higher by forming the Ni plated thin 
layers on the input window and the intermediate metal ring superposed 
parts in the manner as mentioned immediately hereinabove. As the same thin 
Ni plated layers may be employed, the manufacture is rendered easy and the 
airtight junction may be effected in a sure manner. As the washer ring can 
be strongly attached, the peripheral portion of the input window is 
further reinforced. 
In the above embodiments, description has been made on the case where the 
thin metal layer to be interposed between the input window and the 
intermediate metal ring to be airtightly joined is composed of Ni; 
however, the metal to be employed for the thin metal layers is not 
restricted to Ni; a material as shown in Table 1 or a combination thereof 
may be employed to give a stable junction by applying heat and pressure. 
TABLE 1 
______________________________________ 
Thin metal layer to be 
Thin metal layer to be 
formed on surface of 
formed on surface of 
Refer- Al material of input 
Fe material of inter- 
ence window mediate metal ring 
______________________________________ 
I Cu plated layer None 
II Cu plated layer Cu plated layer 
III None Cu plated layer 
IV Ni plated layer None 
V None Cu layer plated on Ni 
plated layer 
VI None Al deposited layer 
VII None Al layer deposited on 
Ni plated layer 
VIII None Al layer deposited on 
Cu plated layer 
______________________________________ 
Appropriate temperatures and pressures of the junction portion during the 
bonding by heating and pressure include those as mentioned hereinabove 
when the Ni plated layer is formed, and junction temperatures of 
310.degree. C. at a pressure of 960 kg/cm.sup.2 and 500.degree. C. at a 
pressure of 520 kg/cm.sup.2 are appropriate when the Cu plated layer is 
formed. It is appropriate to apply a temperature ranging from 250.degree. 
C. to 650.degree. C., preferably from 350.degree. to 500.degree. C. and a 
pressure ranging from 250 to 1,500 kg/cm.sup.2, preferably from 800 to 
1100 kg/cm.sup.2. When the Al deposited layer is employed, its thickness 
may by 300 .mu. or less and, preferably, 1 to 2 .mu.. 
The embodiments shown in FIGS. 8 to 10 have the following constructions. 
The intermediate metal ring 42 of Fe material having a half section in the 
form of a crank is provided with a thin Ni plated layer 45, and the inner 
flat portion 42c of the intermediate metal ring is provided with a 
intermediate Al ring 53 of Al material having a half section in an 
L-shaped form. The washer ring 50 with the Ni plated layer is mounted on 
the intermediate Al ring, disposed between the lower and upper press 
apparatuses 48 and 49, respectively, and joined by applying heat and 
pressure in the same manner as in the above embodiments. With the washer 
ring 50 disposed at the lower side, the peripheral portion 41 of the input 
window 24 fits inside the intermediate Al ring 53, and the peripheral 
portion and an upper end portion 53a of the intermediate Al ring 53 are 
welded airtightly over the whole periphery by a method such as AC-TIG 
welding. Reference numeral 54 in the drawing indicates a welded portion of 
Al material formed as a projection by the airtight welding. 
This embodiment of the vacuum container has a construction in which the 
intermediate ring 53 of Al material and the intermediate metal ring 42 of 
Fe material are bonded by applying heat and pressure and then the 
intermediate ring 53 and the input window, both made of Al material, are 
welded. The washer ring 50 is employed for ensuring the hot 
pressure-bonding between the intermediate Al ring 53 and the intermediate 
metal ring 42 of Fe material. As the airtight welding between the 
intermediate ring and the input window, both made of Al material, is 
effected easily, it is effective to prevent deformation of the input 
window. 
FIG. 11 illustrates an embodiment in which an outer side surface 53b of the 
intermediate Al ring 53 having a half section in an L-shaped form is 
arranged slightly separated from the inner side surface of the 
intermediate metal ring 42 of Fe material. The outermost periphery of the 
peripheral portion 41 of the input window 24 is folded parallel to the 
axis of the tube and along the end portion 53a of the intermediate Al ring 
53, thereby airtightly welding the whole periphery of the two portions as 
shown by reference numeral 54. As the welded portion 54 is provided 
separately from the inner side surface of the intermediate metal ring 42, 
the welding can be performed easily and the airtight welding to the input 
window can be conducted with only a local rise in temperature. Thus, 
deformation of the input window can be controlled. 
In the embodiments illustrated in FIGS. 12 and 13, the body portion 25 of 
the vacuum container consists of a cylinder 55 composed of Al material of 
the vicinity of the input side 24 and integrated with portions of larger 
diameter and of smaller diameter; a middle Al ring 56 composed of Al 
material; an intermediate metal ring 57 composed of Fe material; a sealing 
ring 58 of Fe material capable of being readily airtightly joinable with 
glass or ceramic; and the glass or ceramic insulator 25a of the output 
portion. The intermediate Al ring 56 and the intermediate metal ring 57 of 
Fe material are bonded by applying heat and pressure through one or more 
layers of Ni, Cu or Al to flanges 56a and 57a folded so as to be in 
contact with the inner side of the tube at a plane perpendicular to the 
axis of the tube, as in the embodiments hereinbefore set forth. As shown 
in FIG. 13, both the flanges 56a and 57a are placed between the lower and 
upper press apparatuses 48 and 49, respectively, and are fixed by 
inserting a two-part hard metal ring 59 in order to prevent deformation of 
the outer periphery. They are then joined by applying heat and pressure. 
Then, both the outer peripheral portion 41 of the input window 24 and the 
flange 55a folded toward the outside of the cylinder 55, both made of Al 
material, are subjected to AC-TIG welding as shown by reference numeral 
60. Both the lower flange 55b of the cylinder 55 and the flange 56b folded 
toward the outside of the intermediate Al ring 56 are also subjected to 
AC-TIG welding, as shown by reference numeral 61. The last step of closing 
the vacuum container in an airtight manner is to subject the middle metal 
ring 57 and the sealing ring 58, both made of Fe material, to AC-TIG 
welding at each of the outer flanges 57b and 58a, respectively, as shown 
by reference numeral 62. As this welding can be conducted outside the 
container using same materials, an airtight junction can be formed in a 
sure and easy manner. 
The embodiment illustrated in FIG. 12 is characterized by forming the body 
constituting a portion of the vacuum container by airtightly joining it 
with rings of Al and Fe material or other kinds of materials. This 
embodiment is applicable to a structure containing one or more sealed 
junctions of the Al material with the Fe material between the input window 
of Al material and the output portion insulator of glass or ceramic. 
As mentioned hereinabove, the vacuum container of the present invention is 
formed by utilizing a hot pressure-bonding in connecting an input window 
of Al material, or a intermediate ring of another Al material to be joined 
to the input window, to a intermediate metal ring of Fe material to be 
airtightly joined to glass or ceramic, with one or more metal plated 
layers selected from the group consisting of Ni, Cu and Al formed on the 
surface one or both of the Al material and the Fe material, thereby 
joining them in an airtight manner. Accordingly, the present invention can 
provide a sealed junction at a low cost and in a stable way so that it is 
suitable for mass production. As the hot pressure-bonding can be conducted 
by abutting a washer ring as a supplemental metal ring against Al 
material, the airtight junction can be formed in a surer way to realize a 
radiation image multiplier tube having a more practical application 
because it can reinforce relatively soft Al material.