Preparation of a one-curie 171Tm target for the detector for advanced neutron capture experiments (DANCE)

Abstract

Approximately one curie of 171Tm (T1/2 = 1.92a) has been produced and purified for the purpose of making a nuclear target for the first measurements of its neutron capture cross section. Target preparation consisted of three key steps: (1) material production; (2) separation and purification; and (3) electrodeposition onto a suitable backing material. Approximately 1.5 mg of the target material (at the time of separation) was produced by irradiating ca. 250 mg of its stable enriched 170Er lanthanide neighbour with neutrons at the ILL reactor in France. This production method resulted in a “difficult-to-separate” 1:167 mixture of near-neighboring lanthanides, Tm and Er. Separation and purification was accomplished using high-performance liquid chromatography (HPLC), with a proprietary cation-exchange column (Dionex, CS-3) and alpha-hydroxyisobutyric acid (α-HIB) eluent. This technique yielded a final product of ∼95% purity with respect to Tm. A portion (20 μg) of the Tm was electrodeposited onto thin Be foil and delivered to the Los Alamos Neutron Science Center (LANSCE) for preliminary analysis of its neutron capture cross section using the Detector for Advanced Neutron Capture Experiments (DANCE). This paper discusses the major hurdles associated with the separation and purification step, including scale-up issues related to the use of HPLC for material separation and purification of the target material from α-HIB and 4-(2-pyridylazo)resorcinol (PAR) colorant.