MULTIDETECTOR CALIBRATION FOR MASS SPECTROMETERS

The international Atomic Energy Agency's Safeguards Analytical Laborat ory has performed calibration experiments to measure the different eff iciencies among, multi-Faraday detectors for a Finnigan-MAT 261 mass s pectrometer. Two types of calibration experiments were performed: (i) peak-shift experiments and (ii) peak-jump experiments. For peak-shift experiments, the ion intensities were measured for all isotopes of an element in different Faraday detectors. Repeated measurements were mad e by shifting the isotopes to various Faraday detectors. Two different peak-shifting schemes were used to measure plutonium (UK Pu5/92138) s amples. For peak-jump experiments, ion intensities were measured in a reference Faraday detector for a single isotope and compared with thos e measured in the other Faraday detectors. Repeated measurements were made by switching back-and-forth between the reference Faraday detecto r and a selected Faraday detector. This switching procedure is repeate d for all Faraday detectors. Peak-jump experiments were performed with replicate measurements of Pu-239, Re-187, and U-238. Detector efficie ncy factors were estimated for both peak-jump and peak-shift experimen ts using a flexible calibration model to statistically analyze both ty pes of multidetector calibration experiments. Calculated detector effi ciency factors were shown to depend on both the material analyzed and the experimental conditions.