Cold Electron Sources for Low Size Weight and Power Mass Spectrometers

Electron emitters are key components of many instruments with scientific, industrial, or medical applications. The first stage of mass spectrometers involve ionizing the sample by electron impact at high energy. Presently, the default source of electrons in most cases are hot filament cathodes. Hot filaments have a number of drawbacks, including high power draw, heating, high vacuum requirements, gradual burn-out, and a wide range of emitted electron energies. For space-based applications, they are not replaceable. Long lifetime cold cathodes have been a goal for decades. Field emitters such as Spindt and CNT emitters are the most prominent. They rely on a sharp tip to enhance electric fields to eject electrons. However they also eject their tip material and have short lifetimes. Metal-Insulator-Metal tunneling cathodes impart the energy to escape into vacuum by accelerating electrons as they tunnel across an insulator towards a thin top metal exposed to vacuum. We are designing and fabricating a similar structure involving a semiconductor, insulator, and a 2D material top electrode. The insulator is designed for stability, low defect density, and high tunneling current. The top electrode creates a tunneling potential across the insulator without the need for scattering metal films that can damage the insulator. The top of the insulator will be in contact with the 2D material, which is very stable and will not diffuse into the insulator, which is the biggest contributor to this type of device degradation and failure. In addition to these desirable properties, our device is fabricated on-chip using semiconductor processing methods. Importantly, they will take less than 15 volts to operate. This is extremely low power, as the tunneling current is 10 mA/cm2, so operating the device takes 150 of milliwatts/cm2 in contrast to a hot filament, which uses 5 or more watts/cm2, and the field emitters, which require extremely high voltages. Mass spectrometers are essential for planetary science and crewed missions: they provide crucial insights into atmospheric composition, surface chemistry, and potential signs of life. Existing hot filament electron sources are fragile, power-hungry, and prone to burnout, creating single-point failures. Guardion’s on-chip cold emission tunneling cathode emitter solves these issues by delivering microamp-level emission from a 100 μm × 100 μm device, eliminating high-temperature failure modes and allowing operation in higher pressures. Fabricated with standard silicon processes, these cold cathodes reduce Size, Weight, and Power (SWaP), while redundancy on a single chip boosts reliability. With a narrower electron energy spread, they can improve resolution by up to 30% compared to hot filaments. Operation without strict vacuum constraints opens new mission architectures. This innovation directly aligns with decadal survey calls for robust, low-power in situ instruments, replacing bulky electron sources with a single-chip solution for future missions to Mars, icy moons, and beyond.

This proposed cold cathode electron source technology directly supports NASA’s mission directives by enabling more robust, efficient, and versatile mass spectrometers across a wide range of planetary, lunar, and terrestrial missions. Traditional hot cathode filaments consume high power, require large vacuum systems, and pose single-point failure risks—limitations that can jeopardize science objectives or demand redundant hardware. By contrast, our 2D-material-based cold cathode design delivers the necessary emission current while drastically reducing power consumption and overall system size, weight, and power (SWaP). These improvements align with the Decadal Surveys “Visions and Voyages for Planetary Science 2020–2030” and “Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023–2032,” both of which emphasize the need for advanced in situ instruments that can detect organics, salts, and minerals under harsh and varied conditions. In eliminating the high-temperature failure modes of conventional electron sources, our approach also extends instrument lifetimes, enables operation at higher pressures, and removes a key mission-limiting component. This, in turn, supports more ambitious mission architectures—such as exploring subsurface oceans on icy moons or the rugged terrains of small solar system bodies—with fewer resources devoted to bulky power supplies and vacuum constraints. Additionally, feedback from NASA centers like JPL confirms a clear demand for a microamp-level cold cathode source capable of boosting mass spectrometer resolution and durability. Taken together, this innovation offers a vital pathway for NASA’s next-generation analytical instruments—helping achieve critical science goals while reducing risks and costs in the quest to understand our solar system and safeguard future crewed missions. By eliminating high temperature filaments and large vacuum requirements, our cold cathode electron source technology enables smaller, more efficient, and more durable mass spectrometers suited to a wide range of commercial markets. In pharmaceutical research and drug discovery, portable mass spectrometers with lower size, weight, and power (SWaP) could be deployed for real-time compound identification and process control—reducing turnaround times and enhancing on-site decision-making. Similarly, in clinical and biomedical settings, this innovation supports point-of-care diagnostic tools and rapid analyses of patient samples, potentially improving patient outcomes by accelerating treatment decisions. In forensic toxicology and homeland security, field-ready mass spectrometers capable of quick setup and continuous operation can be used for detecting trace chemicals at crime scenes, ports of entry, or large public events—without the fragility or high power demands of traditional hot filament sources. Environmental monitoring also stands to benefit: cold cathode-based instruments can be deployed in remote or challenging environments to track pollutants, monitor water quality, or survey air composition in near real-time, aiding regulatory compliance and public health initiatives. Meanwhile, industries such as food safety and agriculture can harness these next-generation systems to detect contaminants or verify product quality on-site rather than sending samples to distant labs. The improved durability and broader operational envelope of cold cathode sources open new commercialization opportunities for both established and emerging analytical instrumentation providers. By reducing the bulk, cost, and maintenance demands typically associated with electron impact ionization, this technology paves the way for affordable, high-performance, and adaptable mass spectrometers that can serve an ever-expanding customer base—from field researchers, border agents, to hospital techs.

This is a mature technology (TRL 7+) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

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