A progressively reduced pretension method to fabricate Bradbury-Nielsen gates with uniform tension

A Bradbury-Nielsen gate (BNG) is often used to modulate ion beams. It consists of two interleaved and electrically isolated sets of wires with uniform tension, which can keep parallel, equidistant, and coplanar over a wide temperature range, making the BNG reliable and robust. We have previously analyzed the non-uniform problem of wire tensions with sequentially winding method, and developed a template-based transfer method to solve this problem. In this paper, we introduced a progressively reduced pretension method, which allows directly and sequentially winding wires on the substrate without using a template. Theoretical analysis shows that by applying proper pretension to each wire when fixing it onto the substrate, the final wire tensions of all wires can be uniform. The algorithm and flowchart to calculate the pretension sequence are given, and the fabrication process is introduced in detail. Pretensions are generated by weights combination with a homebuilt weaving device. A BNG with stainless steel wire and a printed circuit board substrate is constructed with this method. The non-uniformity of the final wire tensions is less than 2.5% in theory. The BNG is successfully employed in our homemade ion mobility spectrometer, and the measured resolution is 33.5 at a gate opening time of 350 {\mu}s. Compared to the template-based method, this method is simpler, faster and more flexible when making BNGs with different configurations.