With inert helium gas that slows fast-moving ions and high-amplitude RF fields that actively stabilize the position of the ions, the sample ions are trapped within a "trapping potential well" along the central axis of the STorIT and RIG (depicted by the line of red and blue spheres above). As the ions move within the trapping region at a secular frequency, an alternating current (AC) is applied through the "AC Electrode". This signal resonates with the ions' secular frequency, allowing kinetic energy to grow until the ions leave the STorIT to the CIT through the gap between the electrodes. Ions with sufficiently moderate kinetic energy become trapped within the CIT, successfully transferring them from one ion trap to another. Ions with too little energy return to the STorIT, and ions with too much energy fly through the CIT, terminating elsewhere.

 

Using the same process of harmonious resonant ejection, the ions can be ejected from the CIT to a detection setup (not shown). Currently, this system employs a conversion dynode and electron multiplier tube pair. Ions that impact the conversion dynode cause secondary electron emission. These electrons then travel through a large potential difference to the electron multiplier tube, which amplifies the electrons into an electric current that an oscilloscope can detect.

Since this process occurs over a few hundred milliseconds and ions are selectively ejected by mass sequentially over time, the result is a desired mass spectrum.

 

Project Goals:

As mentioned earlier, the three ion trap geometries are well established in the literature. Which raises the question: If these ion traps have been previously demonstrated, why combine them? Each geometry has its advantages and disadvantages, and when integrated, they can offer greater value than their contributions.

 

The RIG and the STorIT provide larger ion storage capacities than the CIT's specific point storage, though they sacrifice some mass resolution. The CIT takes advantage of the central void in a toroidal ion trap, where there are typically no electrodes. In previous studies developing precursor devices, the central axis of a Toroidal Ion Trap (TorIT) is used to house the detection equipment; however, in this new configuration, the CIT occupies that central space, and the detection hardware is placed elsewhere. 

 

When these three geometries are combined, they enable "tandem" mass analysis, allowing for various simultaneous analyses. The RIG provides a long, straight axis for the electron beam, which ionizes sample gases along its length. The STorIT, as its acronym suggests, stores sample ions and selectively transfers them into the CIT. When a targeted mass is isolated in the CIT from the bulk sample, a mass analysis process called "collisionally induced dissociation" occurs. In this process, the target ion is fragmented as it collides with itself and the surrounding buffer gas, producing fragment ions that create a unique molecular fingerprint. This fingerprint can be used to identify the parent target ion further. 

 

Combining a high-storage ion trap with a high-resolution tandem mass analyzer has significant implications for the miniaturization of ion trap-based mass analyzers. As the size of the devices decreases, the quantity of ions that can be stored also shrinks. The combined geometry of the SCIT can help overcome the challenges associated with miniaturization, paving the way for portable ion traps. With portable mass analyzers, we can envision various applications that could benefit from in situ mass analysis, such as uncrewed submarines, aircraft, or spacecraft, field drug analysis by police officers, continuous monitoring of pollutants, and tracer compounds for detecting leaks in oilfields.

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