Recent developments in resonance ionization mass spectrometry for ultra-trace analysis of actinide elements

Abstract

Resonance ionization mass spectrometry is an efficient tool to detect minute amounts of long-lived radio-isotopes in environmental samples. Applying resonant excitation and ionization with pulsed laser radiation within a hot cavity atomizer enables the sensitive detection and precise quantification of long-lived actinide isotopes. Due to the inherently element selective ionization process, this method ensures ultimate suppression of contaminations from other elements and molecules. The characterization of in-source resonance ionization of the actinide elements U, Th, Np, and Am using a compact quadrupole mass spectrometer (QMS) setup are discussed.

Highly selective two-step laser ionization schemes for the analysis of actinide mixtures

“…Since the actinides have different evaporation curves and vapor pressures at a given temperature, the mass spectra were measured at different heating temperatures, corresponding The uncertainty of the atom numbers is ≤ 10%. This element composition is close to that determined in spent fuel rods of WWER-440, WWER-1000 and RBMK-1000 reactors [3] to optimum release of an element into an atomic gas (A, C measured at 1210(5) • C and B, D measured at 1490(5) • C). The temperature of the atomizer was measured through a window of the vacuum chamber with a two colour pyro meter.…”

“…The development of the ionization schemes of uranium, plutonium, and americium and their characterization in a multi-element mixture were performed at the Mainz atomic beam unit (MABU), applying a quadrupole mass spectrometer in combination with a pulsed Ti:sapphire laser system [3]. The sample solution of typically 3 μL is pipetted onto a 5x5 mm 2 zirconium foil with 0.025 mm foil thickness and then placed inside a tantalum tube furnace of 30 mm length and 3 mm diameter, which is heated resistively to the optimum evaporation temperatures of the actinides under study which all amount to about 2000 K. At sufficiently high temperatures, the sample atoms are evaporized and subsequently resonantly ionized by the incident laser beams.…”

“…The experimental setup as shown in Fig. 1 is identical to the one previously used for the development of three-step ionization schemes and for ultra-trace analysis of actinides [3]. Two-step ionization schemes with high efficiency and reasonable element selectivity were identified, simplifying the experimental expenditure and enhancing long term reliability significantly.…”

“…The temperature of the atomizer was measured through a window of the vacuum chamber with a two colour pyro meter. 3 The spectra A and B were measured using the laser scheme for resonant ionization of plutonium, with specific tuning for the isotope 241 Pu. The mass spectra show the expected signal ratios for all plutonium isotopes 239,240,241,242 Pu.…”

Terbium Medical Radioisotope Production: Laser Resonance Ionization Scheme Development

“…The LARISSA team of Mainz University operates two specific experimental setups for atomic spectroscopy and R&D on resonance ionization and isotope separation. The Mainz Atomic Beam Unit (MABU) is a compact quadrupole mass spectrometer ( 24 ), well-suited for spectroscopic analysis, which was used in this work to develop a suitable laser ionization scheme for Tb. The RISIKO setup ( 23 ) is a 30 keV beam energy electromagnetic off-line mass separator (in the experiment, the mass resolution was about 150 for the region of Tb isotopes), which serves as a substitute of the CERN-MEDICIS mass separator due to their widely similar experimental arrangement.…”