Mass spectrometers, other than those specified in 0B002.g. or 3A233, capable of measuring ions of 200 atomic mass units or more and having a resolution of better than 2 parts in 200, as follows, and ion sources therefor: a. Inductively coupled plasma mass spectrometers (ICP/MS); b. Glow discharge mass spectrometers (GDMS); c. Thermal ionisation mass spectrometers (TIMS); d. Electron bombardment mass spectrometers which have a source chamber constructed from, lined with or plated with ‘materials resistant to corrosion by uranium hexafluoride UF 6 ’; e. Molecular beam mass spectrometers having either of the following characteristics: 1. A source chamber constructed from, lined with or plated with stainless steel or molybdenum and equipped with a cold trap capable of cooling to 193 K (– 80 °C) or less; or 2. A source chamber constructed from, lined with or plated with materials resistant to UF 6 ; f. Mass spectrometers equipped with a micro-fluorination ion source designed for actinides or actinide fluorides.