Abstract:
A procedure for polishing slit blades to ensure proper flatness and blade angle. This task is incredibly difficult. The number of strokes, series of and type of abrasive papers used, direction of polishing lapping strokes, as well as other practices to promote flatness and minimize human and manufacturing error in the final slit blade product have all been experimentally determined by ADC personnel over years of experience and study. A fixture for holding blades while polishing the blade angle side has been developed to accommodate precise blade angle polishing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not applicable 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable 
       SEQUENCE LISTING OR PROGRAM 
       [0003]    Not applicable 
       BACKGROUND OF THE INVENTION 
       [0004]    In synchrotron research using x-rays, the x-ray beam size and shape is defined by a device called a slit. The slit defines an aperture through which the x-rays may pass through, by using blades made of materials that will absorb x-rays. 
         [0005]    The blades are typically attached to actuators that can change the shape of the aperture via computerized command to the actuator motors. These slit blades require the highest precision in terms of flatness and blade angle. 
         [0006]    By creating a polishing process to redefine flatness and blade angle lost due to use, new blades can be re-used. This is a cost effective way to maintain apertures requiring slits. 
       SUMMARY OF THE INVENTION 
       [0007]    The device described herein is a slit blade polishing procedure developed to maximize the precision of blade flatness and blade angle. 
         [0008]    Slit blades need to have a smooth matte finish and a sharp, defect free knife edge in order to achieve the best possible focus of the beam passing through the aperture. 
         [0009]    The process involves the use of several different sized grit paper, including silicon carbide paper and poly-crystalline diamond suspensions on fabric, application of pressure, compressed air, and a final polish with colloidal silica. 
         [0010]    The benefits of the implementation of such a process include substantial cost savings due to the ability to re-use slit blades after polishing, as opposed to total replacement, and maximization of precision of slit blade flatness and angle to provide the most accurate beam focus. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]    The invention as described herein with references to subsequent drawings, contains similar reference characters intended to designate like elements throughout the depictions and several views of the depictions. It is understood that in some cases, various aspects and views of the invention may be exaggerated or blown up (enlarged) in order to facilitate a common understanding of the invention and its associated parts. 
           [0012]      FIG. 1  shows a schematic representation of a slit as used in the synchrotron industry. 
           [0013]      FIG. 2  shows an internal schematic representation of a slit used in the synchrotron industry. 
           [0014]      FIG. 3  shows the beam side of the slit blade. 
           [0015]      FIG. 4  shows the backside of the slit blade. 
           [0016]      FIG. 5  shows a side view of the slit blade. 
           [0017]      FIG. 6  shows the parallel direction of lap strokes during the polishing procedure as well as alternated direction between grit paper sizes. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0018]    Provided herein is a detailed description of one embodiment of the invention. Therefore, specific details enclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or manner. 
         [0019]    The slit blade polishing technique in place at ADC consists of a step-by-step procedure in which slit blades of varying sizes and shapes are polished and finished in order to perform optimally. 
         [0020]      FIG. 1  shows a schematic representation of a slit used in the synchrotron industry. Within this schematic representation are the blades  7  in which the polishing procedure explained herein is implemented upon. The aperture  8 , or opening, is also shown. The opening diameter and shape is changed using several slit blades. The accuracy to which the diameter and shape of the aperture can perform is highly dependent upon the polishing and finishing of the slit blades. Slit blade widths vary from 10 to 35 mm and thickness of 1.5 to 12 mm. Blades used in ADCs slit assemblies are made from either Tungsten or Tantalum. Blades  7  and aperture  8  of the overall slit is also shown in  FIG. 2 . This figure simply shows the internal schematic representation in order to show location of slit blades within the slit, more accurately. 
         [0021]      FIGS. 3 ,  4  and  5  show different views of one type, size and shape, of slit blade in which this polishing procedure would be performed on. Specifically,  FIG. 3  shows the beam side  9  of the slit blade, removed from the slit apparatus with the angle side  10  of the slit and 2° angle edge  11  of the slit blade.  FIG. 4  is a view of the back side  12  of the slit blade with reference to the angle side  10  and 2° angle edge  11  of the slit blade.  FIG. 5  is a side view of the slit blade, better demonstrating the angle side  10  and 2° angle edge  11 ; with view of the beam side  9  of the blade. 
         [0022]    The following contains the step by step procedure of the slit blade polishing process with reference to slit blade components represented numerically as explained previously. 
         [0023]    The beam side  9  is polished using progressively decreasing paper grit size, demonstrated as follows: 180, 240, 320, and then 400 grit size. During this step, downward pressure is applied to the blade center during lapping; one lap is equivalent to a forward and backward stroke across the blade. Five to eight lap strokes are completed for each paper grit size, demonstrated in  FIG. 6 . 
         [0024]    Staring with the first grit, 180, lapping is done left to right, or right to left. For each progressive grit paper, lapping direction is alternated to promote flatness, compensating to a degree, for what is known as human error, also demonstrated in  FIG. 6 . Lap strokes are done parallel to the knife edge with incremental moves sideways as lapping progresses, keeping the knife edge trailing in order to retain blade flatness. Once this is completed, the blade is blown off with compressed air to remove any remaining material removed during polishing. 
         [0025]    Next, the attention is moved to the 2° angle side  10  of the slit blade. This side is not the critical side to be polished in this process, however, the polishing of this side aides in the sharpness of the edge  11  created between the beam side  9 , where the incident beam actually strikes when blades are within the slit apparatus, and angle side  10 , which increases sharpness and accuracy of the beam created as it passes through the opening  8  created by several different slit blades within the complete device. 
         [0026]    The angle fixture is placed on 0.002″ stainless steel shims and clamped in with one to four blades, depending on how many are used for the system. This is done to maintain parallelism. A backing plate is used between the back side of the blades and the swivel head set screws in order to prevent bending of the blades during polishing. If multiple blades are clamped together during this process, the blades are to be protruding evenly, ˜0.002″ from the bottom of the fixture. 
         [0027]    The angle side  10  of the blades are then polished identical to the beam side  9  of the blade, using progressively decreasing paper grit size, demonstrated as follows: 180, 240, 320, 400, 600, 800 then 1200. During this step, downward pressure is applied during lapping; one lap is equivalent to a forward and backward stroke across the blades angle side. Five to eight lap strokes are completed for each paper grit size. Lap strokes are done parallel to the knife edge with incremental moves sideways as lapping progresses, keeping the knife edge trailing in order to retain blade flatness, demonstrated in  FIG. 6 . 
         [0028]    Starting with 180 grit paper, lapping is done left to right, or right to left. For each progressive grit paper, lapping direction is alternated to promote flatness, compensating to a degree, for what is known as human error. Final polishing of the blade angle side  10  is done using 1200 grit silicon carbide paste on a tungsten lapping plate. After this, attention is returned to the beam side of the slit blade. 
         [0029]    The beam side  9  is polished using progressively decreasing paper grit size, demonstrated as follows: 600, 800 and then 1200. After this, the slit is blown off with compressed air in order to remove any remaining material, removed during the polishing process. Starting with 600 grit paper, lapping is done left to right, or right to left. For each progressive grit paper, lapping direction is alternated to promote flatness, compensating to a degree, for what is known as human error. Final polishing of the blade beam side  9  is done using 1200 grit silicon carbide paste on a tungsten lapping plate, after which, is reviewed under a microscope, checking for a flat and matte finish with a defect free knife edge. 
         [0030]    During the entire polishing process, it is essential that there are no air bubbles beneath the grit paper, and that blades are blown off with compressed air between each grit type. 
         [0031]    At the end of any grit phase, flatness can be checked by applying water and observing the water bead formed. If the polished surface is flat, the surface tension of the water will cause it to bead from edge to edge. If the polished surface is waned off, decreasing in flatness or slightly rounded downward or upward, the water will stop at the beginning of the angle change. When it is apparent that the blades polished surface is not flat, the blade is re-flattened, starting with 320 grit paper, and following the successive steps as listed above.