The Nu Plasma High Resolution Multi-Collector ICP Mass Spectrometer (Nu Instruments Inc.) at the UCD Center features a double focusing Nier Johnson design. With this approach, compensation of the ion beam energy spread leads to a high quality image. The mass spectrometer comprises an electrostatic analyser (ESA) followed by a magnetic sector. Unique to the Nu Plasma are the quadrupole lenses placed between the magnet and Faraday collector array that can act as a zoom lens to alter the dispersion of the instrument thus removing the necessity for movable collectors.  The Nu Plasma can be used for either solution or solid sampling.

The standard mass resolution of a typical modern high precision mass spectrometer such as Nu Plasma is approximately 400. At this resolution, the instrument produces flat top peaks that are essential for high precision isotopic measurements whole maintaining a good sensitivity. For many elements, molecular species can be generated which can cause interferences on the mass spectrum. These can become a problem for accurate isotopic ratio determination. The Nu Plasma at the UCD Center is equipped with two high resolution modes: pseudo-high (partial) resolution (if the interferences are on the same side of the peak), and high resolution. With a compromise in sensitivity by a factor of 10 typically, a mass resolution of 8000 could be achieved, therefore certain interfering molecular species could be resolved from the isotope peak of interest.

To achieve accurate and precise isotope ratio measurements good instrument abundance sensitivity is essential. This ensures that the tailing of large isotopes do not impinge on smaller adjacent isotopes causing inaccurate isotope ratio measurements. The analyzer vacuum of the Nu Plasma is maintained at 2E-9 mbar supported by three ion pumps, which is essential to remove tailing effect. Typical abundance sensitivity of the Nu Plasma is 4ppm at -1amu. With the retardation lens filter, 500ppb (-1amu) and 50 ppb (-2amu) are further achieved.