Cold cathode gauge head

The electrons in the cold cathode gauge are created by a high voltage self-sustaining discharge. The arrangement of the electric and magnetic fields causes electrons to travel long distances in spiral paths before they are collected on the anode. Long electron trajectories enhance the ionization probability and improve sensitivity. The discharge begins when one electron or ion gains sufficient energy to ionize a gas molecule. Since the gauge has no filament, the discharge is initiated by stray field emission or external events (cosmic rays or radioactive decay). At low pressures, this can take minutes and cold cathode gauges are usually switched on at high pressures. When the temperature is constant, the gauge reading is proportional to pressure. The gauge is sometimes called a Penning gauge and it is used for the region from 10−2 to 10−10 Torr.

The exhibit is cold cathode gauge head IKR 050 manufactured by Balzers AG (Liechtenstein). It has an inverted magnetron design with a metal pin (anode) surrounded by a measurement chamber (cathode). A cylindrical permanent magnet is used to generate a magnetic field within the chamber. The pictured gauge served in MALDI-TOF mass spectrometer Reflex IV (Bruker Daltonics) manufactured in the 2000s.

Wikipedia: Pressure measurement