Thermal Ionization Mass Spectrometry (TIMS)

Overview

What is TIMS?

Thermal ionization mass spectrometry (TIMS) is designed to obtain high precision isotopic information. Ions are created by passing a current through a thin metal ribbon or ribbons under vacuum. The ions generated are accelerated under vacuum to a magnetic sector where the ions are separated according to their m/z ratio and a detection system. Comparison of signals corresponding to individual ion beams yield precise isotope ratios.

Our latest generation of thermal ionization mass spectrometry is based on more than 40 years of experience in variable multicollector instrumentation and combines innovative features like amplifiers equipped with 10¹³ ohm feedback resistors, with field-proven technology such as thermal ionization source, variable multicollector system, dual retarding potential quadrupole (RPQ), and compact secondary electron multipliers. We offer flexible and complete multicollector packages that can be configured to best suit the application, including dual detectors (Faraday/electron multiplier), multiple ion counters, and RPQs. The 10¹³ ohm amplifiers add to the flexibility and enable scientists to quantify small ion beams on Faraday Cups.

Isotope ratio mass spectrometry

What are the advantages of TIMS?

TIMS has several major advantages relative to other isotope ratio techniques:

It produces ions with a restricted range of energies; this means high precision measurements can be obtained with abundance sensitivity in the ppb range
The ionization source is highly stable, leading to highly precise isotope ratios
Samples can be ionized and evaporated at different temperatures allowing multiple isotope systems to be measured on a single filament, e.g. U-Pb
Mass fractionation is lower and more consistent average, allowing measurements to be made without standard-sample bracketing
Operation of filament heating and measurement can be fully automated
Near 100% transmission of ions from source to collector
Both positive and negative ions can be produced, allowing a greater variety of isotope systems to be measured e.g. Os and W

Applications

Geochronology

Geochronology is the dating of a specific geologic event through the use of radioactive decay in closed systems. For terrestrial systems, common TIMS applications in geochronology and radiogenic tracer studies involve:

Rb-Sr
K-Ca

Sm-Nd
U-Th-Pb

Common lead
Re-Os
Radiogenic tracers of Sr, Nd, Pb, Hf and Os

Cosmochemical

In cosmochemical systems, the measurement of isotopic compositions is primarily as tracers of nucleosynthetic processes and constraining the evolution of the solar system. This involves measurement of the systems noted above, but also includes the decay of short-lived radionuclides, as observed principally in meteorites. Systems of cosmochemical interest using TIMS include:

Mn-Cr
Hf-W

Pd-Ag
Nucleosynthetic anomalies of Ca, Cr, Sr, Zr, Mo, Ba, Nd, Pd and Sm

Tracer studies

Tracer applications refer to the use of the growth of naturally occurring isotopes to evaluate the interaction between geochemical systems and/or reservoirs. Non-radiogenic (stable) isotope-isotope ratios are typically used to characterize exchange processes, track reservoir interactions, and evaluate biologic and kinetic processes (e.g. B, Ca, Cr, Mo, Sr).

Nuclear safeguards

Reliable analysis of the isotope composition of nuclear materials provides key information for nuclear safeguarding and nuclear forensics. Systems of nuclear interest include:

U
Sr
actinides
lanthanides

Measuring ⁹⁰Sr Abundances in Environmental Samples by Thermal Ionization Mass Spectrometry

Geochronology