Design and laboratory-accessible manual fabrication of a Bradbury-Nielsen gate for ionic liquid electrospray thruster...

Time-of-flight mass spectrometry (TOF) is widely adopted to characterize the charged particles emitted from ionic liquid electrospray thrusters (ILETs). The Bradbury-Nielsen gate (BNG) offers advantages such as high geometric transparency and low control voltage, making it particularly suitable for bipolar beam measurements of ILETs in TOF systems. However, BNG fabrication poses significant challenges, including poor controllability of interwire spacing, non-uniform wire tension, and insufficient mechanical fixation reliability. In this work, an integrated and laboratory-accessible BNG structure and a corresponding manual fabrication method are presented. The completed BNG exhibits an average measured wire spacing of 0.505 mm (standard deviation 0.018 mm), representing a 1% deviation from the design value of 0.5 mm, and a transparency of 76%. Experimental characterization demonstrates that voltage pulse rise time remains below 63 ns with the control voltage in the range of 500-1500 V. The BNG was further evaluated in an ILET-relevant TOF setup. For gate voltages ≥800 V, the beam blocking efficiency exceeded 95% for both positive and negative beam polarities. These results demonstrate that the proposed design achieves competitive gating performance through a fabrication route accessible to common laboratories, making it a practical solution for TOF diagnostics of ILETs.