Abstract: A controlled aperture ball drop includes a ball cartridge that is mounted to a frac head or a high pressure fluid conduit. The ball cartridge houses a ball rail having a bottom end that forms an aperture with an inner periphery of the ball cartridge through which frac balls of a frac ball stack supported by the ball rail are sequentially dropped from the frac ball stack as a size of the aperture is increased by an aperture controller operatively connected to the ball rail.

Abstract: A controlled aperture ball drop includes a ball cartridge that is mounted to a frac head or a high pressure fluid conduit. The ball cartridge houses a ball rail having a bottom end that forms an aperture with an inner periphery of the ball cartridge through which frac balls of a frac ball stack supported by the ball rail are sequentially dropped from the frac ball stack as a size of the aperture is increased by an aperture controller operatively connected to the ball rail.

Abstract: A controlled aperture ball drop includes a ball cartridge that is mounted to a frac head or a high pressure fluid conduit. The ball cartridge houses a ball rail having a bottom end that forms an aperture with an inner periphery of the ball cartridge through which frac balls of a frac ball stack supported by the ball rail are sequentially dropped from the frac ball stack as a size of the aperture is increased by an aperture controller operatively connected to the ball rail.

Abstract: A controlled aperture ball drop includes a ball cartridge that is mounted to a frac head or a high pressure fluid conduit. The ball cartridge houses a ball rail having a bottom end that forms an aperture with an inner periphery of the ball cartridge through which frac balls of a frac ball stack supported by the ball rail are sequentially dropped from the frac ball stack as a size of the aperture is increased by an aperture controller operatively connected to the ball rail.

Abstract: A method and apparatus for generating a molecular or atomic fluorine jet or beam under vacuum for etching surfaces. The apparatus uses a hollow crystalline tube preferably fabricated from a crystal of a Group II fluoride such as magnesium fluoride. A terminal portion of the tube is heated to over 1000.degree. C. and a mixture of fluorine gas and an inert carrier gas is induced under pressure into the tube. An atomic fluorine jet is emitted from the opposite end of the tube. The jet can be collimated into a beam and can be directed at masked surfaces for selective etching of the surface. The atomic fluorine source has a very high intensity resulting in rapid etching of materials and as a beam is capable of highly anisotropic etching. The jet may be primarily molecular fluorine if the tube is heated to a lower temperature.

Abstract: Apparatus for positioning objects for microscopic examination includes a stage module which may be attached to standard microscope, and a control module. The stage module is comprised of a translating stage, a rotating stage, and a pair of rotating sample holders. The translating stage is movable horizontally in a linear direction, and the rotating stage is carried on the translating stage for rotational movement about a vertical axis. The rotating sample holders may be rotated about their centers, and they are linked together so that their rotational movements are equal in magnitude but opposite in direction. The respective movements of the translating stage, the rotating stage and the rotating sample holders are controlled by the control module.