Method of manufacturing boron coated straws for neutron detection through spiral winding and welding

An improved continuous process for forming boron coated straws for use in neutron detectors comprising the steps of:

• providing a reel of boron-coated film, an elongated mandrel having an outside diameter approximately equal to the desired inside diameter of the straws to be formed, a belt drive system comprising at least one belt and two motor driven capstans, a laser welding system, a laser velocimeter, and a scissor mechanism for cutting;
• spiral winding the boron-coated film around the elongated mandrel such that the boron-coating is adjacent to the mandrel and the outside edge of each wind of film overlaps the previous wind by no more than about 0.5 millimeter;
• maintaining a tension on the film reel to ensure a forcible backwards pull on the film as it wraps around the mandrel;
• wrapping the belt around the mandrel on top of the overlapped foil;
• rotating the belt using the motor driven capstans to rotate and translate the spirally wound and overlapping film down the mandrel;
• welding the overlapped edge of the spirally wound film to form a seam using a laser welding system as the film advances down the mandrel thereby creating a cylinder;
• measuring the speed at which the newly formed cylinder advances down the mandrel with the laser velocimeter
• using the speed measurement to determine the proper time to cut the cylinder to achieve the desired length;
• and
• cutting the cylinder with a scissor mechanism at the determined proper time thereby forming a boron-coated straw of the desired length.

An improved apparatus for forming boron coated straws for use in neutron detectors comprising:

• a reel of boron-coated film, the film having a width;
• a fixed, elongated mandrel, the mandrel being positioned such that as the boron-coated film is drawn off the reel, it will spirally wrap around the mandrel with an overlap;
• a guide pin having beveled guides at each end with a width approximately equal to the film width, the guide pin guiding setting a consistent overlap of the film as it spiral wraps around the mandrel;
• a belt drive system comprising at least one belt and two motor driven capstans, the belt drive system rotating the film to spirally wrap the film about the mandrel and translating film along the fixed, elongated mandrel;
• a microscopic fiber laser for welding a seam formed at the overlap of the spirally wound film as the film rotates and translates, thereby forming a cylinder;
• a laser velocimeter for measuring the speed at which the cylinder;
• and
• a scissor mechanism for cutting the cylinder at the desired length.