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.
Faraday Cup Detector
Meaning
Charge collection device that measures the intensity of an ion or electron beam by converting the incident particle flux into an electrical current. The faraday cup detector provides a simple and robust method for quantitative analysis in mass spectrometry. It consists of a conductive cup connected to an electrometer.
Operating Principle
Incoming ions strike the inner surface of the collector and are neutralized by a flow of electrons from the ground. This faraday cup detector current is directly proportional to the number of charges arriving per unit of time. It allows for high precision measurements of absolute ion quantities.
Detection Sensitivity
Escape of secondary electrons from the surface during impact can lead to measurement errors. A faraday cup detector often incorporates a negatively biased electrode to push these electrons back into the cup.
Material Selection
Selecting the correct metal for the collector is necessary for maintaining measurement accuracy. A faraday cup detector is usually constructed from gold or stainless steel to minimize surface oxidation and chemical reactivity. These materials provide a stable work function which is necessary for consistent electron emission properties.
The internal geometry of the cup is designed to be deep and narrow to trap as many secondary particles as possible. This physical design reduces the reliance on electronic suppression alone.