Electron beam array for surface treatment

Abstract

An array of electron beam tubes is mounted on a conductive plate for projecting strip-like electron beams through air onto a substrate beneath the plate. The tubes each have a narrow beam window formed by a very thin low-Z film layer, supported by silicon and sealing the tube against ambient pressure. Such windows produce low beam attenuation and allow low extraction voltages to be used, thereby reducing beam energy which would otherwise be lost by penetration through a surface to be treated. The stripe-like output electron beam segments may be formed into a linear beam track so that the entire widthwise extent of a surface, such as a sheet or web, may be treated by electron beam irradiation or the beam segments may be formed into any desired composite beam pattern. In another embodiment the stripe-like output beam segments may be arranged in an array to treat a circular circumferential surface, such as a cable.

I claim: 
     
       1. An electron beam generating apparatus comprising, a support plate mounting a plurality of electron beam tubes in an array, each tube emitting a stripe-like electron beam through an electron beam permeable, low-Z, gas impermeable window, the tubes arranged in the array so that the stripe-like electron beams form modular beam segments of a desired beam pattern directed away from the support plate into an air atmosphere and onto a surface to be treated.   
     
     
       2. The apparatus of claim 1 wherein said window comprises a silicon membrane. 
     
     
       3. The apparatus of claim 1 wherein the electron beam tube comprises, a vacuum tube envelope having a base end and a window end longitudinally spaced apart from the base end, the window end having .[.a thin, electron beam permeable, carbide or nitride film, gas impermeable, window therein.]. .Iadd.said electron beam permeable, gas impermeable window therein, said window being thin, carbide or nitride film and .Iaddend.having a specified major dimension across the window end of the tube envelope,   an extended filament transversely disposed within the tube envelope proximate to the base end and generating electrons, and   a beam forming electrode means disposed proximate to the extended filament for shaping an extended, stripe-like shape electron beam from said electrons wherein the extended shape of the electron beam is oriented parallel to the major dimension of the window, and   a beam acceleration electrode means proximate to said film for projecting said electron beam through said window as a linear stripe-like beam, the beam having an energy less that 125 kV.   
     
     
       4. The electron beam generating apparatus of claim 3 wherein the .[.electron acceleration.]. .Iadd.beam forming .Iaddend.electrode .Iadd.means .Iaddend.has a cylindrical parabolic shape. 
     
     
       5. The electron beam generating apparatus of claim 3 wherein the extended filament is an elongated linear filament. 
     
     
       6. The electron beam generating apparatus of claim 3 wherein the electron beam permeable window has an elongated linear shape. 
     
     
       7. The electron beam generating apparatus of claim 3 wherein the electron beam permeable, gas impermeable window is a thin layer of silicon carbide. 
     
     
       8. The electron beam generating apparatus of claim 3 wherein the electron beam permeable, gas impermeable window is a thin layer of silicon nitride or boron nitride or doped silicon. 
     
     
       9. The electron beam generating apparatus of claim 3 wherein the .[.elongate.]. .Iadd.extended, stripe-like shape electron .Iaddend.beam has an extent of at least one centimeter. 
     
     
       10. The electron beam generating apparatus of claim 1 wherein said support plate is planar. 
     
     
       11. An electron beam generating apparatus comprising, a support plate mounting a plurality of electron beam tubes in an array, each tube emitting a stripe-like electron beam through an electron beam permeable, low-Z, gas impermeable window, the tubes arranged in the array so that the stripe-like electron beams form modular beam segments of a desired beam pattern directed away from the support plate into an air atmosphere and onto a surface to be treated, and   means for measuring the output of each tube.   
     
     
       12. An electron beam generating apparatus comprising, a support plate mounting a plurality of electron beam tubes in an array, each tube emitting a stripe-like electron beam through an electron beam permeable, low-Z gas impermeable window, the tubes arranged in the array so that the stripe-like electron beams form modular beam segments of a desired beam pattern directed away from the support plate into an air atmosphere and onto a surface to be treated, wherein beam tubes of said arrays are grouped in different sections having different output beam energy in each section.   
     
     
       13. An electron beam generating apparatus comprising, a support plate mounting a plurality of electron beam tubes in an array, each tube emitting a stripe-like electron beam through an electron beam permeable, low-Z, gas impermeable window, the tubes arranged in the array so that the stripe-like electron beams form modular beam segments of a desired beam pattern directed away from the support plate into an air atmosphere and onto a surface to be treated wherein the electron beam tube includes,   a vacuum tube envelope having a base end and a window end spaced apart from the base end, the window end having a thin, electron beam permeable, carbide or nitride film, gas impermeable, window therein having a specified length across the window end of the tube envelope,   an extended filament disposed within the tube envelope proximate to the base generating electrons, and   a beam forming electrode means disposed proximate to the extended filament for shaping an extended, stripe-like shape electron beam from said electrons wherein the beam forming electrode has a forward baffle defining a beam aperture between the extended filament and the window and the extended shape of the electron beam is oriented parallel to the length of the window, and   a beam acceleration electrode means proximate to said film for projecting said electron beam through said window as a linear stripe-like beam, the beam having an energy less than 125 kV.   
     
     
       14. An electron beam generating apparatus comprising, a support plate mounting a plurality of electron beam tubes in an arrays, each tube emitting a stripe-like electron beam through an electron beam permeable, low-Z, gas impermeable window, the tubes arranged in the array so that the stripe-like electron beams form modular beam segments of a desired beam pattern directed away from the support plate into an air atmosphere and onto a surface to be treated, wherein said support plate is triangular with beam tubes directing electron beams inside of the triangle defined by the support plate.   
     
     
       15. An electron beam generating apparatus comprising, a plurality of electron beam tubes, each tube having a window end spaced apart from a base end, the window end having a thin, elongated, electron permeable, low-Z, gas impermeable window penetrated by a stripe-like electron beam,   a support means for holding the beam tubes in an array spaced such that the stripe-like electron beams from the plurality of tubes emerge from said windows and sweep the entirety of a linear track spaced apart in air from the window ends of the tubes, and   a beam current monitor connected to each tube.   
     
     
       16. The electron beam generating apparatus of claim 15 wherein said support means comprises a planar or triangular plate means. 
     
     
       17. The electron beam generating apparatus of claim 15 further comprising a material handling table having a length and a width, spaced apart from said support plate, having means for advancing material past said plurality of electron beam tubes. 
     
     
       18. The electron beam generating apparatus of claim 17 wherein the means for advancing material operates in a direction wherein said track is parallel to the length of the table. 
     
     
       19. The electron beam generating apparatus of claim 17 wherein the means for advancing material operates in a direction wherein said track is parallel to the width of the table. 
     
     
       20. The electron beam generating apparatus of claim 15 further comprising spaced apart material handling rollers defining a plane having a specified width, the plane being spaced apart from said support plate, the rollers advancing material in a direction past said plurality of electron beam tubes such that said track is transverse to said direction. 
     
     
       21. The electron beam generating apparatus of claim 15 wherein the electron beam permeable, gas impermeable window is a thin layer of silicon nitride or boron nitride or doped silicon. 
     
     
       22. An electron beam generating apparatus comprising, a plurality of electron beam tubes, each tube having a stripe-like beam and a window end spaced apart from a base end, the window end having a thin electron beam permeable, low-Z, gas impermeable window therein having a specific length across the window end of the tube envelope accommodating the stripe-like beam, and   a support means for holding the beam tubes in an array spaced such that the stripe-like electron beams from the plurality of tubes emerge from said windows and sweep the entirety of a linear track spaced apart in air from the window ends of the tubes, said support means including a plate means for contacting the window end of said tubes, said plate means carrying an electrical potential in insulated relation for each tube.   
     
     
       23. The electron beam generating apparatus of claim 22 wherein said plate means comprises an insulative sheet with conductive traces, at least one trace connected to each tube, wherein a voltage may be applied to each tube. 
     
     
       24. An electron beam generating apparatus comprising, a vacuum tube envelope having a base end and a window end spaced longitudinally apart from the base end, the window end having a thin, electron beam permeable, low-Z, gas impermeable window therein having a specified length across the window end of the tube envelope,   an extended filament disposed transversely within the tube envelope proximate to the base end and generating electrons, and   a beam forming electrode means disposed proximate to the extended filament for shaping an extended, stripe-like shape electron beam from said electrons wherein the extended shape of the electron beam is oriented parallel to the length of the window, and   a beam acceleration electrode means proximate to said film for projecting said electron beam through said window as a linear stripe-like beam.   
     
     
       25. The electron beam generating apparatus of claim 24 wherein the electron beam permeable, gas impermeable window is a thin layer of silicon nitride or boron nitride or doped silicon.