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.
Secondary Electron Multiplier
Meaning
Electronic component that amplifies a low intensity ion or electron signal through the process of secondary emission. The secondary electron multiplier uses a series of electrodes called dynodes to increase the signal by several orders of magnitude. Each dynode is held at a higher potential than the previous one.
Amplification Factor
Impact of a single particle on the first dynode releases multiple secondary electrons. These electrons are accelerated to the next dynode in the secondary electron multiplier where the process repeats. A single ion can generate a pulse of millions of electrons at the final anode.
This massive gain allows for the detection of individual particles arriving at the detector. It is particularly useful in isotope analysis where the concentration of the target ion might be extremely low. The gain is controlled by adjusting the voltage across the dynode chain.
Noise Threshold
Signal intensity is measured as either a current or a series of pulses. While a secondary electron multiplier provides high sensitivity for trace analysis, it can saturate if the incident beam is too intense.
Surface Degradation
Gradual loss of amplification efficiency occurs as the dynode surfaces age. Routine calibration of the secondary electron multiplier is required to compensate for this gradual change in gain over time.