A large Bradbury Nielsen ion gate with flexible wire spacing based on photo-etched stainless steel grids and its characterization applying symmetric and asymmetric potentials

TL;DR

This paper introduces a novel large-scale Bradbury Nielsen ion gate constructed from photo-etched stainless steel grids, offering adjustable wire spacing and simplified assembly, tested for ion beam switching in mass spectrometry applications.

Contribution

The paper presents a new design of Bradbury Nielsen gates using photo-etched grids, enabling easier construction and adjustable wire spacing for large beam sizes.

Findings

Successfully constructed a large gate covering 900 mm²

Demonstrated effective switching with symmetric and asymmetric potentials

Validated performance at TRIUMF's ion trap facility

Abstract

Bradbury Nielsen gates are well known devices used to switch ion beams and are typically applied in mass or mobility spectrometers for separating beam constituents by their different flight or drift times. A Bradbury Nielsen gate consists of two interleaved sets of electrodes. If two voltages of the same amplitude but opposite polarity are applied the gate is closed, and for identical (zero) potential the gate is open. Whereas former realizations of the device employ actual wires resulting in difficulties with winding, fixing and tensioning them, our approach is to use two grids photo-etched from a metallic foil. This design allows for simplified construction of gates covering large beam sizes up to at least 900\,mm$^2$ with variable wire spacing down to 250\,\textmu m. By changing the grids the wire spacing can be varied easily. A gate of this design was installed and systematically tested at TRIUMF's ion trap facility, TITAN, for use with radioactive beams to separate ions with different mass-to-charge ratios by their time-of-flight.