Enhanced ionization efficiency in TIMS analyses of plutonium and americium using porous ion emitters

Abstract

Investigations of enhanced sample utilization in thermal ionization mass spectrometry (TIMS) using porous ion emitter (PIE) techniques for the analyses of trace quantities of americium and plutonium were performed. Repeat ionization efficiency (i.e., the ratio of ions detected to atoms loaded on the filament) measurements were conducted on sample sizes ranging from 10-100 pg for americium and 1-100 pg for plutonium using PIE and traditional (i.e., a single, zone-refined rhenium, flat filament ribbon with a carbon ionization enhancer) TIMS filament sources. When compared to traditional filaments, PIEs exhibited an average boost in ionization efficiency of ∼550 % for plutonium and ∼1100 % for americium. A maximum average efficiency of 1.09 % was observed at a 1 pg plutonium sample loading using PIEs. Supplementary trials were conducted using newly developed platinum PIEs to analyze 10 pg mass loadings of plutonium. Platinum PIEs exhibited an additional ∼134 % boost in ion yield over standard PIEs and ∼736 % over traditional filaments at the same sample loading level.

Americium isotope analysis by Thermal Ionization Mass Spectrometry using the total evaporation method

“…Another advantage of TIMS analyses is the possibility to perform concentration determination by isotope dilution (ID-MS) with low uncertainty, lower than 1 % [10][11][12]. TIMS is frequently used for actinides isotope composition determination [6,7,[13][14][15][16][17][18], in particular for uranium and plutonium [4,5,8,[19][20][21][22]. On the other hand, americium metrological isotope analysis are rare, due to the lack of Certified Reference Material (CRM) [5].…”

Graphene Oxide Carburization Enhanced Ionization Efficiency for TIMS Isotope Ratio Analysis of Uranium at Trace Level

“…As the mass ratio of Re powder and GO was raised, the ionization efficiency increased slightly and then reached a plateau (Figure ), illustrating that Re powder could promote the formation of Re-carbide in the GO layers, generating a better property for ion emitting. It also provides another possibility for further improvement of ionization enhancer by integrating other ion emitters with this porous layered nanomaterial. − …”

“…Although this method could get an ionization efficiency of 0.2–0.3% for uranium and was much more reproducible, it always required a special vacuum instrument to expose the filaments to benzene vapor at high temperature, which is time-consuming, expensive and has a potential risk of benzene toxicosis. Recently, a porous ion emitter (PIE) technique was developed for the analysis of trace quantities of actinides. − Rhenium and platinum powders were mixed in a gluing agent, and then heated to form a porous Pt/Re alloy as the thermal ionization emitter. Although the preparation was a little time-consuming and required operation skill, these works showed the porous micro- and nanostructures of ion emitter could remarkbly enhance the ion yields.…”

Graphene-based filament material for thermal ionization

“…Research has been done to try and increase ionization efficiencies with much of the work focused on geometry modifications of the typical rhenium filament material. [7][8][9] Because of thermodynamic limits related to work function of the analyte and the ionizing filament entirely new materials (i.e. not Re or W) are needed in order to greatly improve ionization efficiency.…”