Cold cathode ionization vacuum gauges

Cold cathode ionization gauges are discharge tubes, however a little bit di fferent, due to the additional magnetic field generated by an external perm anent magnet. In standard discharge tubes residuary gas pressure is proport ional to ionization current in the pressure range 1-0,01 mbar. However, wit h the reduction of gas density, the value of the current decreases and come s to zero at about 10(-3) mbar. When adding a magnetic field to such tubes, due to the increased length of the trajectories of electrons, avalanche io nization of the gas molecules is maintained even at a much lower gas pressu re. Measuring low ionisation currents, pressures in the range between 10(-3 ) - 10(-6) mbar can be assessed. There are various configurations of cold c athode vacuum gauges, and some optimised designs reach a usefull pressure r ange of 10(-8) mbar and lower. In the article the basic operating principle s and modem types of such vacuum gauges are described, and the prototype of IEVT design is presented.