Making electrical connections inside a vacuum chamber to a stack of electron and ion optical components using the conventional approach of discrete wires is not efficient because: (1) the separate wires must be insulated from each other and the interior structures; (2) the wires must be spot welded or mechanically secured at their end points to the electrical feedthroughs and optical components, both of which are typically bulky and prone to failure in vibration; and (3) the wires are a major source of failure in high-G applications.
The solution to this problem required two coupled problems to be solved. The design of electron and ion optics must ensure both proper transport and focusing of the charged particles, together with the mechanical problem of ensuring robust and implementable electrical connections. An iterative approach was developed using proprietary and commercial charged particle fields and trajectories coding to design a proper lens stack, together with mechanical computer-aided design (CAD) to make as optimized and miniature a system as possible. The results were implemented on two versions of ion trap mass spectrometers being developed at JPL: a “full-size” quadrupole ion trap with characteristic dimension r0 = 1 cm, and a miniature trap with r0 = 0.45 cm.
The mechanical structures that mount and constrain the electron and ion optics are also used to make electrical connectivity. The mechanical supports are patterned in such a way to plug directly into the vacuum feedthrough contacts, so that during assembly, the entire system is held tightly in compression. This robust arrangement is highly beneficial for instruments that must withstand high- G loads.