Tritium-compatible cryogenic pellet gas gun
A tritium-compatible pellet gas gun for a deuterium-tritium (D-T) pellet fueling apparatus is provided. In one aspect, the tritium-compatible pellet gas gun includes a pellet sizer assembly that provides in situ adjustment of pellet length during injector operation. The pellet sizer assembly includes a guillotine slide that is actuated by a pusher tube, the guillotine slide being operable to restrict the orifice of the extruder nozzle to reduce pellet length with fine resolution. The tritium-compatible pellet gas gun also includes dual flexible metal bellows seals that maintain hermetic separation between the D-T fuel region, a guard vacuum, and the ambient environment, while still permitting linear motion. This configuration allows the pellet length to be reduced by up to 50% without venting or warming the D-T pellet fueling apparatus.
1 . A tritium-compatible gas gun for producing cryogenic fusion fuel pellets from a solid extrusion ribbon as the solid extrusion ribbon is discharged from an extruder through an extruder nozzle opening, the gas gun comprising:
a pellet sizer assembly including an adjustable guillotine slide that is configured to restrict the extruder nozzle opening, the guillotine slide being an elongated rectangular member, the pellet sizer assembly further including a first flexible metal bellows seal and a second flexible metal bellows seal;
wherein the first flexible metal bellows seal includes series-connected bellows on either side of a first flange, the second flexible metal bellows seal includes series-connected bellows on either side of a second flange, the first flange being coupled to the second flange via a pusher tube, and the second flange being rigidly coupled to the guillotine slide, such that lateral movement of the first flange causes lateral movement of the second flange via the pusher tube, thereby causing lateral movement of the guillotine slide to at least partially restrict the extruder nozzle opening;
a cutter assembly including a cutter solenoid housing, a cutter tube, a plunger operatively coupled to a first solenoid coil, and a spring assembly to absorb return shock from the plunger;
a gun barrel concentrically disposed within the pusher tube and configured to receive pellets that have been cut from the solid extrusion ribbon by the cutter tube; and
a propellant valve assembly including a valve body, a second solenoid coil, a shuttle armature that is operatively coupled to a valve tip such that energization of the second solenoid coil causes the valve tip to unseat from a valve seat, and a return spring configured to reseat the valve tip and maintain seal tightness when the second solenoid coil is deenergized.
2 . The gas gun of claim 1 , wherein the pusher tube extends outside of a guard vacuum chamber for positioning the guillotine slide.
3 . The gas gun of claim 1 , wherein the adjustable guillotine slide of the pellet sizer assembly is configured to reduce fuel pellet length by up to 50%.
4 . The gas gun of claim 1 , wherein the first flexible metal bellows seal is positioned to separate a guard vacuum from an ambient environment.
5 . The gas gun of claim 4 , wherein the second flexible metal bellows seal is positioned adjacent the extruder to separate the guard vacuum from a deuterium-tritium (D-T) fuel environment.
6 . The gas gun of claim 1 , wherein the spring assembly includes a metal wave spring and metal washer, the metal wave spring being positioned to absorb return shock from the plunger.
7 . The gas gun of claim 1 , wherein the shuttle armature of the propellant valve assembly is free-floating relative to the valve tip.
8 . The gas gun of claim 1 , wherein the valve body of the propellant valve assembly consists entirely of stainless steel.
9 . The gas gun of claim 1 , wherein the valve body of the propellant valve assembly includes a first end portion joined to a second end portion by a square groove weld.
10 . A method of producing and injecting cryogenic fusion fuel pellets with a tritium-compatible gas gun, the method comprising:
sizing a pellet by actuating an adjustable guillotine slide to restrict an orifice of an extruder nozzle, the guillotine slide being sealed by a first metal bellows seal and a second metal bellows seal, wherein the guillotine slide is an elongated rectangular member, and wherein each of the first metal bellows seal and the second metal bellows seal includes series-connected bellows on either side of a flange, the flange of the first metal bellow seal being coupled to the flange of the second metal bellows seal by a pusher tube that surrounds a gun barrel, such that lateral movement of the first metal bellows seal causes lateral movement of the second metal bellows seal via the pusher tube, thereby causing lateral movement of the guillotine slide;
cutting the pellet from a solid extrusion by plunging a cutter tube into the solid extrusion and absorbing a return shock of the cutter tube with a metal spring assembly; and
propelling the pellet through the gun barrel, the gun barrel being concentrically disposed within the pusher tube, by energizing a solenoid coil to draw a shuttle armature toward a valve body to lift a valve tip from a valve seat, and thereafter reseating the valve tip with a return spring when the solenoid coil is deenergized to maintain seal tightness.
11 . The method of claim 10 , wherein the first metal bellows seal separates a guard vacuum from an ambient environment.
12 . The method of claim 11 , wherein the second flexible metal bellows seal separates the guard vacuum from a deuterium-tritium (D-T) fuel environment.
13 . The method of claim 10 , wherein the guillotine slide is actuated to reduce pellet length by up to 50%.
14 . The method of claim 10 , wherein absorbing the return shock comprises compressing a metal wave spring disposed in the cutter assembly.
15 . The method of claim 10 , wherein the shuttle armature of the propellant valve assembly is maintained free-floating relative to a valve tip.
16 . The method of claim 10 , wherein the valve body of the propellant valve assembly is formed entirely of stainless steel.
17 . The method of claim 10 , further comprising monitoring cutter operation by measuring shock loads with a shock accelerometer coupled to the cutter assembly.