Patent Number: 045445206
Section: description

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION Reference is now made to FIGS. 1 and 3 which show a pair of crosshairs 12 and 14 which preferably comprise glass having a diameter from 5 .mu.m to 10 .mu.m but which can be 2 .mu.m or less in diameter affixed to a target plate 16. Crosshairs 12 and 14 cross at point 18. The crosshairs are affixed together to the target holder by means of a glue such as a fast setting epoxy. All manipulation of the crosshairs, microsphere and target shells is readily accomplished with a fast taper, fine tipped probe such as a single bristle brush of beagle hair. Work is done under a microscope positioned to be looking down on the target, i.e., perpendicular to and positioned above or below the target as seen in FIGS. 1, 2 and 3. A microballoon 20 is affixed tangentially at an equator or great circle to each of the crosshairs by glue or epoxy such as that which holds the crosshairs to the target plate 16. It will be noted that the microballon 20 is not affixed about crosspoint 18 but rather rests in a quadrant formed by crosshairs 12 and 14. Therefore, each surrounding shell in order to incorporate the microsphere at its center as desired will be slightly displaced from having its center aligned on crosspoint 18. It will be understood by those skilled in the art that this misalignment from the crosspoint will be extremely small because the microballoons are on the order of 100 .mu.m in diameter. Also, since the microballoon is fixed in the horizontal plane, its vertical position may be accurately adjusted by a temporary 90.degree. rotation of the sample holder under the microscope. After the glue holding microsphere 20 to crosshairs 12 and 14 has been allowed to dry sufficiently, microsphere 20 is not easily displaced from its proper position. A first shell 22 is fabricated utilizing two hemispheres. A first hemisphere, as seen in FIG. 4, is glued to the underside of the crosshairs as seen by the microscope under which the target structure is fabricated, and the second hemisphere is affixed over the first so that they mate to form a sphere which is glued to the crosshairs. A second shell 24 is affixed to crosshairs 12 and 14 as was shell 22. Further, a shell 26, seen in FIG. 2, is similarly affixed on crosshairs 12 and 14 about shells 22 and 24. It will be appreciated by those skilled in the art that any number of shells can be affixed about one another as hemispheres glued to crosshairs 12 and 14 so that microballoon 20 occupies the common center of all such shells and that if the fibers cause an undesirably large separation of the shells at the equator, the shells can be notched to accommodate the fibers. In practice, spherical shells are cut into hemispheres. Two glass fibers are glued to the target holder to form crosshairs. The equator of a microballon is glued tangentially to each of the crosshairs. One of the hemispheres is glued to the crosshairs concentric to the microballoon. The target holder is turned over and the second hemisphere is aligned with and glued to the first hemisphere to form a spherical shell having the microballoon positioned at its center. The target provided by the method of this invention provides greater stability for shells and the shells are more consistently and accurately centered about microballoon 20 than is possible with existing methods of target fabrication. The various features and advantages of the invention are thought to be clear from the foregoing description. However, various other features and advantages not specifically enumerated will undoubtedly occur to those versed in the art, as likewise will many variations and modifications of the preferred embodiment illustrated, all of which may be achieved without departing from the spirit and scope of the invention as defined by the following claims.