Model 'rocket' incorporating a quadrupole mass spectrometer head, by staff at 20th Century Electronics Ltd, England, 1973. Presented to Gilbert Tomes: founder of 20th Century Electronics Ltd. The quadrupole mass spectrometer head uses electrostatic and electromagnetic deflecting fields to determine the atomic weight of an element, which may be used to find out if it is radioactive. The quadropole mass spectrometer was first made public in 1968. The mass spectrometer, which measures both total and partial pressures, is a very important tool which can be used to warn of contamination.