New type of drift tubes for gas-discharge detectors operating in vacuum: Production technology and quality control

A device for fabricating thin-wall (straw) drift tubes using polyethylene terephthalate film 36 $\mu$m thick by ultrasonic welding is described together with the technique for controlling their quality. The joint width amounts to 0.4–1.0 mm. The joint breaking strength is 31.9 kg/mm$^{2}$. The argon leakage from a tube of volume 188.6 cm$^{3}$ under a pressure gradient of 1.0 atm does not exceed 0.3 × 10$^{–3}$ cm$^{3}$/min, which is mainly related to the absence of metallization in the joint vicinity. The high strength, the low tensile creep due to the absence of glued layers, the small value of gas leakage makes the new tubes capable of reliable and long-term operation in vacuum, which is confirmed by the operation of 7168 straw tubes for two years in the NA62 experiment.