Microchannel plates (MCPs) having micron and submicron apertures

Abstract

There is disclosed a three draw technique for drawing optical fibers into various cross-sectional shapes. The process employs a glass tube and rod which are fed into a heated furnace. The viscosity of the glass decreases and the glass flows. The glass is pulled or drawn out of the furnace at a different rate than it is fed into the furnace. The resultant drawn fibers are stacked and the process is repeated two more times. By employing three drawing steps one can achieve extremely small fiber faces. The final draw step uses a hexagonal cross-section preform and fibers. From the first drawn fibers three geometrical shapes can be assembled and finally drawn into hexagonal shapes with round fibers which are triangles, rhombohedrials and half hex or trapezoidal shapes. These shapes maintain the hexagonal closely packed space providing the highest density per cross-section. With this high density there is less glass flowing to fill voids thereby reducing distortion within the fabricated MCP. The final reduction ratio of the starting material to the finished device is the product of each reduction ratio of the individual draw steps.

A method for fabricating microchannel plates (MCPs) having submicron to micron diameter channels, comprising the steps of: +P1 feeding a clad glass tube through a furnace at a first given feed rate said furnace providing sufficient heat to cause glass flow, +P1 drawing said glass tube from said furnace at a second drawing rate to produce a smaller diameter fiber according to a first reduction ratio indicative of said first and second rates, +P1 stacking said fibers in a predetermined geometric shape, +P1 feeding said stacked fiber shape through a furnace at a second given feed rate, +P1 drawing said stacked fiber shape from said furnace at a third drawing rate to produce a plurality of smaller diameter shaped fibers at a second reduction ratio, +P1 stacking said shaped fibers in a hexagonal format to provide a hexagonal preform and feeding said hexagonal preform through a furnace at a third given feed rate, +P1 drawing said hexagonal preform from said furnace at a fourth drawing rate to produce a plurality of hexagonal shaped fibers, at a third reduction ratio, +P1 forming said hexagonal fibers into a glass boule, +P1 slicing said boule to form individual microchannel plate slices having submicron to micron channel apertures according to the total combined reduction ratios.  
     
         2 . The method according to claim  1  wherein said first and second reduction ratios are equal.  
     
     
         3 . The method according to  claim 2  wherein said third reduction ratio is at least ten times greater than said first and second ratios.  
     
     
         4 . The method according to claim  1  wherein said predetermined geometric shape is a triangular shaped fiber stack.  
     
     
         5 . The method according to claim  1  wherein said predetermined geometric shape is a rhombihedrial shaped fiber stack.  
     
     
         6 . The method according to claim  1  wherein said predetermined geometric shape is a half hex shaped fiber stack.  
     
     
         7 . The method according to claim  1  wherein the steps of feeding said glass tube includes placing said tube over a etchable glass core rod.  
     
     
         8 . The method according to claim  1  wherein said first and second reduction ratios are each one hundred indicative of the ratio of draw rate to the feed rate.  
     
     
         9 . The method according to  claim 8  wherein said third reduction ratio is 3000.  
     
     
         10 . The method according to claim  1  wherein the total combined reduction ratio is about 30×10 6 .  
     
     
         11 . A microchannel plate (MCP) for use with an image intensifier or similar device, comprising: 
 a wafer fabricated from fused glass fibers and having submicron to micron channel diameters with channel densities of 15 to 30 million per square inch.    
     
     
         12 . The MCP according to  claim 11  wherein said glass fibers are hexagonal shaped fibers.  
     
     
         13 . The MCP according to  claim 11  wherein said wafer is sliced from a boule of fused hexagonal optical fibers which boule is formed by a three draw process, each draw producing a fiber having a smaller diameter as a function of the reduction ratio associated with each draw.  
     
     
         14 . The MCP according to  claim 13  wherein each draw process includes feeding a clad glass member into a furnace, at a first rate to cause a decrease in viscosity of the glass and to draw the glass from the furnace at a second rate with the second rate versus the first rate indicative of said reduction ratio and therefore of the reduction in diameter of the glass member.  
     
     
         15 . The MCP according to  claim 14  wherein the very first draw said glass member is a clad glass tube encircling an etchable core rod for feeding into a furnace at a first feed rate and pulling or drawing from said furnace at a second draw rate to produce first fibers of a given diameter.  
     
     
         16 . The MCP according to  claim 15  wherein said second or next draw said glass member is a predetermined geometric stacked array of said first fibers for feeding into a furnace at another feed rate and pulling or drawing out of said furnace at another draw rate with said rates indicative of a reduction ratio to provide a plurality of smaller diameter second fibers than said first fibers according to said reduction ratio.  
     
     
         17 . The MCP according to  claim 16  wherein said glass member is formed by stacking said second fibers in a hexagonal array and feeding said hexagonal array into a furnace at a given feed rate and pulling or drawing said array out of said furnace at a different draw rate to produce third fibers of a smaller diameter than said second fibers and, packing a predetermined number of said third fibers in a glass tube, and fusing said fibers tube to form a MCP boule having submicron to micron center to center core spacing.  
     
     
         18 . The MCP according to  claim 17  wherein a MCP is formed from said boule by slicing said boule and etching said core to form submicron to micron apertures with channel densities of 15 to 30 million per square inch.  
     
     
         19 . The MCP according to  claim 17  wherein said predetermined geometric stacked array is selected from one of the following, triangular, half hex or rhombihedrial shaped arrays.  
     
     
         20 . The MCP according to  claim 19  wherein said array is found by stacking said first fibers in a selected preform indicative of said geometric format.