Terbium Medical Radioisotope Production: Laser Resonance Ionization Scheme Development

Terbium (Tb) is a promising element for the theranostic approach in nuclear medicine. The new CERN-MEDICIS facility aims for production of its medical radioisotopes to support related R&D projects in biomedicine. The use of laser resonance ionization is essential to provide radioisotopic yields of highest quantity and quality, specifically regarding purity. This paper presents the results of preparation and characterization of a suitable two-step laser resonance ionization process for Tb. By resonance excitation via an auto-ionizing level, the high ionization efficiency of 53% was achieved. To simulate realistic production conditions for Tb radioisotopes, the influence of a surplus of Gd atoms, which is a typical target material for Tb generation, was considered, showing the necessity of radiochemical purification procedures before mass separation. Nevertheless, a 10-fold enhancement of the Tb ion beam using laser resonance ionization was observed even with Gd:Tb atomic ratio of 100:1.

Developments towards the delivery of selenium ion beams at ISOLDE

The production of selenium ion beams has been investigated at the CERN-ISOLDE facility via two different ionization methods. Whilst molecular selenium (SeCO) beams were produced at ISOLDE since the early 1990s, recent attempts at reliably reproducing these results have so far been unsuccessful. Here we report on tests of a step-wise resonance laser ionization scheme for atomic selenium using the ISOLDE Resonance Ionization Laser Ion Source (RILIS). For stable selenium an ionization efficiency of 1% was achieved. During the first on-line radioisotope production tests, a yield of $ \approx 2.4 \times 10^4$≈2.4×104 ions/μC was measured for 71Se+, using a ZrO2 target with an electron impact ion source. In parallel, an approach for extraction of molecular carbonyl selenide (SeCO) beams was tested. The same ion source and target material were used and a maximum yield of $ \approx 3.6\times 10^5$≈3.6×105 ions/μ C of 71SeCO+ was measured.

Measurement of the laser resonance ionization efficiency for lutetium

The development of a highly efficient resonance ionization scheme for lutetium is presented. A laser ion source, based on the all-solid-state Titanium:sapphire laser system, was used at the 30 keV RISIKO off-line mass separator to characterize different possible optical excitation schemes in respect to their ionization efficiency. The developed laser resonance ionization scheme can be directly applied to the use at radioactive ion beam facilities, e. g. at the CERN-MEDICIS facility, for large-scale production of medical radioisotopes.

Detection of the O2 A′3ΔU Herzberg III state by photofragment imaging

Photofragment imaging provides a sensitive method for detection of the O2 A′3Δu Herzberg III state using a one-laser dissociation/ionization scheme combined with velocity map imaging of atomic oxygen photofragments.

Investigation of Optical Ionization of Strontium via 5s21S0 ⟶ 5s5p 3P1° ⟶ 5s5d 3D2 ⟶ 4dnp (or 4ndf, n = 39) for Isotope Selectivity Enhancement

We investigated a promising three-step resonance ionization scheme of strontium (Sr) 5s21S0 ⟶ 5s5p 3P1° ⟶ 5s5d 3D2 ⟶ 4dnp (or 4dnf, n = 39) using the first-step intercombination transition for the enhancement of isotope selectivity. The power broadening observed in the 2nd transition indicates that laser power of less than 0.2 mW is sufficient for saturating this transition. Isotope separation can be successfully expected with application of the 3rd transition due to the narrow width of the 4dnp (or 4dnf, n = 39) autoionization level, paving the way for analysis of trace 90Sr in environmental applications.

Resonance ionization of titanium: high useful yield and new autoionizing states

To facilitate analyses of trace amounts of titanium in atom-limited samples, we established a new three-step resonance ionization scheme. Using time-of-flight mass spectrometry we show that the new scheme can be easily saturated, yields stable isotope measurements, and can achieve an overall useful yield of 18%.