welding 2 fine wires inside end of small tube, capacitance welding? 1

My company produces specialist thermocouples comprising of precious metals. My problem is how best to weld 2 wires of 0.3mm dia, inside a small tube with an inside diameter of 1.0mm. The weld needs to be accurate on the tips of the wires. They are set around 20mm deep inside the tube. Any ideas?? We currently use capacitance welding, we are looking to upgrade either this method or to find another.