New Compact Discrete Dynode Multipliers Integrated into the Thermo Scientific TRITON Variable Multicollector Array

Significance of the topic

The Re-Os isotope system provides vital insights into planetary differentiation and mantle evolution. Low natural abundances of Re and Os in geological materials demand highly sensitive and precise measurements. Negative Thermal Ionization Mass Spectrometry (N-TIMS) achieves ionization efficiencies of 10–20 and is the preferred technique for high precision 187Os/188Os ratio determinations.

Objectives and study overview

This work evaluates a new Multi Ion Counting (MIC) configuration using Compact Discrete Dynode (CDD) multipliers integrated into the Thermo Scientific TRITON TIMS multicollector. The study aims to assess detection efficiency, linearity across wide dynamic ranges, stability, dark noise, and cross calibration robustness for Os isotope ratio measurements.

Methodology

An array of 6–7 mm wide CDD multipliers replaces standard channeltron detectors in the focal plane, enabling parallel detection of OsO3 isotopes at one mass unit spacing. Tests included dark noise characterization, counting efficiency, linearity checks from 1 cps to 1.4 × 106 cps, plateau curve mapping, stability trials at 100 kcps, and source detuning experiments to evaluate calibration robustness. Cross calibration factors were derived from standard measurements and in-run procedures.

Used Instrumentation

• Thermo Scientific TRITON TIMS multicollector
• Compact Discrete Dynode multipliers
• Multi Ion Counting array configuration
• Standard Faraday cups for reference

Main results and discussion

• Dynamic range achieved from 1 cps to 1.4 × 106 cps with linearity better than 0.2 over full range
• Dark noise below 10 counts per minute (typical 0.2 cpm)
• Relative stability drift under 0.2 per hour at 100 kcps
• Peak flatness within 0.2 over ±150 ppm mass span
• Cross calibration factors stable within 0.3 under worst case source detuning
• In-run calibration precision limited by single collector mode; sample/standard calibration yields subpermil reproducibility

Benefits and practical applications

The MIC setup with CDD multipliers allows simultaneous collection of all target isotopes, enhancing detection efficiency and analysis throughput for trace Os determinations. Improved stability and linear response support robust high precision geochronology, petrogenesis, and planetary science studies.

Future trends and potential applications

Future developments may focus on further miniaturization of dynode detectors, integration of ultra high gain amplifiers to unify ion counting and Faraday modes, automated in-run correction algorithms, and extension of MIC approaches to additional isotope systems for streamlined high precision workflows.

Conclusion

The new Compact Discrete Dynode multipliers in a MIC configuration exhibit superior dynamic range, stability, and robustness compared to traditional detectors. Their implementation in the TRITON TIMS platform significantly advances precision Os isotope ratio capabilities, reinforcing critical analytical support for geochemical research.

Reference

Tuttas D, Schwieters JB, Bouman C, Deerberg M. New Compact Discrete Dynode Multipliers Integrated into the Thermo Scientific TRITON Variable Multicollector Array. Application Note 30192. Thermo Fisher Scientific; 2009.