Development of Ultrathin 12 µm Thick Straw Tubes for the Tracking Detector of COMET Experiment

This paper describes the development of a new design of mylar straw tubes, operating in a vacuum, with a diameter of 4.8 mm with extremely thin walls of 12 μm for the COMET experiment. The production process is performed with a special machine using ultrasonic welding technology, which allows the manufacturing of unique new straw tubes from a single mylar tape, coated on one side with 70 nm Al layer. The goal of R&D is to create sufficiently thin-wall straws for modern tracking detectors which can satisfy the main requirements of working in a vacuum and have an excellent momentum resolution. The critical point is preservation of the diameter along the tube and the cylindrical shape after pressurization. These newly developed ultrathin tubes showed excellent parameters in various tests. The stability of the seam area formed during the welding process and uniformity of the diameter determine the proper distribution of the electric field and overall performance. These straws fully satisfied and passed the tests of elasticity and gas leakage (working pressure 1 bar). For the first time unique ultrathin 12 μm thick wall tubes with 4.8 mm diameter are achieved. They have excellent working properties for the COMET experiment purposes.