NASA has expressed a need for advanced neutral particle ionizers to enable the next-generation of neutral particle detectors such as mass spectrometers for the study of Earth-Sun interactions and planetary atmospheres. To fulfil this need, Physical Sciences Inc. (PSI) proposes to develop a fail-safe field emission-based cold cathode ionizer for use in space-based instrumentation.
The cold cathode ionizer features ultra-low electron extraction voltages down to 2 V, emission current densities up to A/cm2 across mm2 emission surfaces, instantaneous switching and negligible thermal load. A unique property of PSI’s proposed cold cathode ionizer is its extreme resistance to the most common failure modes associated with field emission devices. The device is designed with recovery from mechanical and thermal shock as well as resilience against exposure to debris or contamination that might be encountered during its service lifetime. The slow degradation of materials and surfaces encountered in space are inherently compensated for in the design.
In Phase I of the program, PSI will demonstrate the principle of the ionizer, raising its technology readiness level (TRL) from 2 to 3. The cathode fabrication process will be developed and cathodes integrated into a demonstration device for evaluation of critical components and operating parameters. Phase I will culminate in production of a detailed preliminary design for a flight-worthy prototype ionizer. In Phase II, ionizer requirements and capabilities will be finalized. A flight-worthy prototype will be constructed and evaluated. The Phase II program will be exited with the ionizer at TRL 6 and with the prototype delivered to NASA for further evaluation. Following Phase II, PSI will work with NASA to identify opportunities to incorporate the new enabling technology into instrumentation for upcoming missions such as Geospace Dynamics Coupling (GDC), and opportunities for NASA-sponsored technology demonstration flights.
The proposed solution for a cold cathode-based ionizer will find its widest use as a component in mass spectrometers destined for planetary exploration and study. These include the study of Earth, its interaction with the sun and the effects of space weather on its upper atmosphere. It will also find use in missions to sample the watery plumes of the Ocean Wolds such as Europa and Enceladus. Similar capability will enhance efforts to study Mars, Titan and other planets and moons, possible watery plumes or their atmospheres.
Large area cold cathode ionizers have applications in display technology and medical imaging techniques such as time- and spatially-resolved X-ray imaging, which take advantage of electron beam pixilation and instant switching without external beam blanking components. Terrestrial and defense-related mass spectroscopy and communications applications will benefit as well.