US 3151241 A
Description (OCR text may contain errors)
p 1954 KARL-HEINZ HERRMANN ETAL 3,151,241
HEATABLE SPECIMEN CARRIER FOR ELECTRON RADIATION APPARATUS Filed Feb. 2, 1962 arrvr fizz /jars. fljak; Z errwan Wq/fraw Z0666 ,mx w
United States Patent 3 151 241 HEATABLE SPECIMEP I CARRIER FOR ELECTRON RADIATEON APPARATUS Karl-Heinz Herrmann and Wolfram Loebe, Berlin-Zehlen- The invention disclosed herein relates to specimen carrier means for use in connection with electron radiation apparatus and is particularly concerned with a heatable specimen carrier for electron microscopes.
Heatable specimen carriers for electron beam apparatus, especially electron microscopes, are known, such carriers employing for the heating of the specimen a heating coil surrounding the specimen, or else an electrical heating winding freely arranged upon a porcelain cylinder which is positioned for cooperation with the specimen cartridge. Such arrangements have only slight insulation with respect to the surroundings thereof and only low heat conductivity with respect to the specimen, thus suffering from undesirable heat losses, and therefore requiring for the heating of the specimen more power than would otherwise be necessary.
In order to remedy this situation, the specimen carrier employed in connection with another known electron beam apparatus is formed, for example, in band-like manner and traversed by current. Such an arrangement occasions mechanical difiiculties. For example, the hand must be fastened exactly beam-symmetrically owing to the very small aperture formed thereby for the passage of the electron beam. The material of which the band is made is quite brittle, which introduces in repeated operation the danger of band breakage. The fastening of the specimen is in such arrangements likewise bothersome.
These drawbacks are avoided by another known heatable specimen carrier, wherein the specimen cartridge is provided with a small tubular metallic member in which is disposed an insulated, preferably bifilar heating winding, the tubular member being with respect to the cartridge cone heat insulated by means of a heat insulating, generally pot-shaped insert member.
In connection with this latter arrangement, there can occur in operation, that is, during the heating of the specimen, undefined jerky motions of the specimen, resulting from the fact that the individual parts of the specimen cartridge are differently heated, such parts having moreover different coefficients of expansion. The mechanical stability of the cartridge is therefore not secured and the connection between the individual parts can consequently be loosened.
The invention is concerned with a heatable specimen carrier of the above last noted type, and the object thereof is to avoid the disadvantage resulting from the mechanical instability. It is in particular intended to convert the jerky specimen motions into uniform motions which cease upon attainment of a heat balance between the mutually interconnected parts.
The invention realizes this object by mutually biasing or pre-tensioning the metal tubing and/ or the insert member and/or the cartridge cone, by means of elastic elements, preferably spring means. This pre-tensioning offers security against the loosening of the connection between the individual parts at elevated temperature.
Details of the invention will now be described with reference to the accompanying drawing showing an example of an embodiment of a specimen cartridge which is 3,151,241 Patented "Sept. 29, 1964 to be inserted into the specimen table of an electron microscope.
Referring now to the drawing, numeral 1 indicates the cartridge cone which is placed into the specimen table (not shown). To the cartridge cone 1 is fastened the small tubular metallic member 3 made, for example, of titanium, molybdenum or platinum, the fastening being effected by a nut 4 which may be made of the same material, with interposition of a generally pot-shaped insert 2, made, for example, of heat insulating ceramic material. Within the wall of the small tubular metallic member 3 is disposed an insulated heating winding 5 which is preferably made of tungsten wire, such heating winding being bifilar so as to avoid interference fields. The heating current is supplied to the winding 5 over a contact 9 and conductors 8. At the lower end of the tubular member 3 is titted the specimen diaphragm 6 which is held in position by a cap 7, the latter being threaded on the tubular member.
The above described construction of the cartridge makes it possible to effect the cleaning thereof simply by immersion, in an acid or the like, of the tubular member 3 containing the heating winding 5.
There are also provided a generally pot-shaped tensioning member 10 and a compression spring 11, such parts serving, in accordance with the invention, for elastically tensioning the individual parts of the heating cartridge with respect to one another. The pot-shaped tensioning member 10 together with the potshaped insert 2 are for this purpose fastened to the tubular metal member 3, by means of the nut 4, and the member 10 has a head 12 engaged by the outer end of the spring 11, the inner end of such spring engaging a shoulder 13 of the cartridge cone 1 and pressing the cartridge cone against the outer end 14 of the pot-shaped member 2, thus resiliently pretensioning the tubular member 3 against the cartridge cone 1. There is no direct connection between the spring 11, which is advantageously made of non-magnetic heat resistant material, and the heated parts of the specimen cartridge.
Resilient means, for example, in the form of resilient contact rods 15 may be advantageously used for conducting the current to the contact 9.
The invention is not inherently limited to the arrangement of a spring disposed between the cartridge cone 1 and the tensioning member 10 as shown in the example of an embodiment illustrated in the drawing. For example, the tensioning member 10 may be omitted and the spring may be disposed between the lower end of the nut 4 and the inside of the bottom of the pot-shaped insert member 2, such spring surrounding the upper threaded portion of the tubular member 3; alternatively, the spring may be disposed between the upper end of the enlarged portion of the tubular member 3 and the bottom Wall of the insert member 2. In the latter case, suitably shaped auxiliary ceramic means may be interposed for separating the spring from the heated parts of the specimen cartridge. In the alternate embodiments, the wall of the insert member 2 which faces in the direction of radiation, may be metallized so as to provide protection against static charges.
Owing to the substantially rotation symmetrical construction of the arrangement according to the invention, the motions that may occur will extend substantially in the direction of the optical axis of the device. The heating which is effected by heat conduction and heat radiation, from the bifilar heating winding 5, is in the new arrangement very eflicient, owing to the good heat insulation with respect to the specimen table as well as in view of the easy exchangeability of the specimen and the low heat capacity of the parts which are to be heated.
In order to keep the heat radiation of the specimen low,
the specimen diaphragm 6 is so arranged that its conical aperture faces toward the cap 7, such cap having a beam passage openingwhich is as small as possible. As a result, the beam passage openings will embrace a spatial angle, emanating from the specimen, which is as small as possible.
The temperature control can be effected by measuring the heating power supplied to the heating Winding 5, by means of a Watt meter'(not shown).
Changes may be made within the scope and spirit of the appended claims which define what is believed to be new and desired to have protected by Letters Patent.
1. A specimen cartridge for electron radiation apparatus, comprising a cone-shaped tubular cartridge member for insertion into the specimen table of an electron microscope, a first generally pot-shaped insert, made of heat insulating material, disposed within said cone-shaped cartridge member, an elongated tubular metallic specimen holder with the inner end thereof projecting through a hole formed in the bottom wall of said first insert into said cone-shaped cartridge member in the direction of the wide end thereof, the outer end of said specimen holder projecting from said cone-shaped cartridge member at the narrow end thereof and containing at such end an insulated bifilar heater winding for heating said outer end and a specimen disposed at such outer end of the specimen holder, a second generally pot-shaped insert made of heat insulating material arranged within said first insert, means for firmly connecting the inner end of said tubular specimen holder with said second insert, and a compression spring disposed between a part of said sec- 0nd insert and a part of said cone-shaped cartridge member for resiliently pressing a part of said cone-shaped cartridge member in engagement with a part of said first insert, thereby resiliently securing said second insert and the tubular specimen holder in position within said coneshaped cartridge member.
2. A specimen cartridge according to claim 1, wherein said spring is made of non-magnetic temperature resistant material.
3. A specimen cartridge according to claim 2, comprising a specimen diaphragm, a cap member for securing said diaphragm in engagement with said specimen holder at the outer end thereof, such specimen diaphragm having a conical opening formed therein facing with the wide end thereof in the direction of said cap, the latter having a hole formed therein which is as small as possibie, for the passage of the electron beam.
4. A specimen cartridge according to claim 2, comprising resiliently disposed contact means for conducting current to said heating winding.
5. A specimen cartridge according to claim 4, wherein the wall of said first insert, which faces in the direction of radiation, is metallized to provide protection against static charging.
References Cited in the file of this patent UNITED STATES PATENTS 2,266,082 Ruska Dec. 16, 1941 2,356,551 Von Borries et al Aug. 22, 1944 2,479,471 Champaygne Aug. 16, 1949 2,858,444 Leisegang Oct. 28, 1958