Helium Mass Spectrometry Principles for Battery Seal Hermeticity Testing
Helium mass spectrometry isolates sub-micron battery seal defects down to 10-12 mbar·L/s, preventing field electrolyte drying and moisture ingress.
Electron Impact Ionization
Meaning
Ionization method that uses a beam of high energy electrons to produce ions from gas phase molecules. The electron impact ionization process typically employs electrons accelerated to seventy electron volts to maximize the probability of molecular interaction. It is the primary technique used in mass spectrometry for chemical identification.
Interaction Physics
Collisions between the primary electron beam and the target molecule result in the removal of an electron to form a radical cation. While electron impact ionization creates a positively charged parent ion, it also imparts significant internal energy. This energy causes the ion to break apart into predictable fragments.
Fragmentation Pattern
Resulting data shows a unique fingerprint of mass to charge ratios. Because electron impact ionization is highly reproducible, these spectra are compared against digital libraries for substance identification. The technique is particularly effective for small organic molecules found in battery electrolytes.
Researchers use it to identify breakdown products that form during the aging of the cell. By mapping these fragments, it is possible to understand the chemical pathways of electrolyte degradation under high voltage.
Vacuum Constraint
Pressure within the ion source must remain very low to prevent ion molecule reactions. Effective electron impact ionization requires a high vacuum environment to maintain the mean free path of both the electrons and the generated ions.