Electron-ionized atom trapping technology is widely used in mass spectrometry and atomic clocks. The complexity of the trapping configuration operating in an ultra-high vacuum system is driven by demands for ultimate sensitivity, performance, and fundamental science. Consequently, external diagnosis, maintenance, and design verification and validation without opening the vacuum and disassembling the system become increasingly difficult. In these ion trapping configurations, electrical charging of non-metallic materials or opening connections are a hard-to-detect problem, yet can easily compromise the intended trapping potential. More specifically, the JPL Linear Ion Trap Standards (LITS) will benefit from a non-invasive solution for system verification/validation, diagnosis, maintenance, and troubleshooting.
The LITS have drawn a variety of attention in space and ground timekeeping applications, where stability and reliability are highly valued. The methodology provides an external diagnostic procedure for the ion trapping system without breaking the vacuum and/or disassembling the system, which are time-consuming and risky. The procedure may also be applied to other electron-ionized atomic trapping systems that have similar requirements.
The basic idea of the diagnosis is electron beam (E-beam) deflection measurement. The E-beam designed to ionize atoms, and the ion-trapping electrodes, are used as electrical charging sensors to map out the functionality of the ion trap. By varying a DC voltage applied on some of the electrodes and detecting charged voltage on the others, deflection of the electron beam can be analyzed to detect possible electrical charging. The E-beam initial direction is along the axis of the traps for efficient ionization and ion loading. The electrons generated by the filament are accelerated by high voltage. To deflect the E-beam, different levels of DC or AC voltage are added on the electrodes of the interested trapping region, whereas the electrodes in other trapping regions are grounded except for specially chosen electrode(s) for charged voltage detection.
The methodology is the first systematic diagnostic use for the complex ion trapping configuration in LITS. It can be used as an external system check for trapped ion frequency standards, which are now in the process of industrialization. Similar schemes can also be applied to electron beam ionized atom trapping systems such as mass spectrometers, quantum manipulation, and computation systems based on ion trapping technology.