A new measurement of the half-life of 166mHo

How accurate are half-life data of long-lived radionuclides?

We have consulted existing half-life data available in Nuclear Data Sheets for radionuclides with Z < 89 in the range between 30 and 108 years with emphasis on their uncertainty. Based on this dataset, we have highlighted the lack of reliable data by giving examples for nuclides relevant for astrophysical, environmental and nuclear research. It is shown that half-lives for a substantial number of nuclides require a re-determination since existing data are either based on one single measurement, are contradictory or are associated with uncertainties above 5%.

Radiochemical Determination of Long-Lived Radionuclides in Proton-Irradiated Heavy Metal Targets: Part II Tungsten

In this study, proton-irradiated tungsten targets, up to 2.6 GeV, were investigated for the purpose of the experimental cross-section measurements. Radiochemical separation methods were applied to isolate the residual long-lived alpha-emitters ¹⁴⁸Gd, ¹⁵⁴Dy, and ¹⁴⁶Sm and the beta-emitters ¹²⁹I and ³⁶Cl from proton-irradiated tungsten targets. The molecular plating technique has been applied to prepare ¹⁴⁸Gd, ¹⁵⁴Dy, and ¹⁴⁶Sm samples for alpha-spectrometry. Production cross-sections of ¹²⁹I and ³⁶Cl were determined by means of accelerator mass spectrometry. The results are compared with theoretical predictions, obtained with the INCL++-ABLA07 codes, showing good agreement for ³⁶Cl and ¹⁴⁸Gd, while a factor of 4 difference was observed for ¹⁵⁴Dy, similar to the results obtained for tantalum targets.

Optimization of a laser ion source for 163Ho isotope separation

To measure the mass of the electron neutrino, the "Electron Capture in Holmium-163" (ECHo) collaboration aims at calorimetrically measuring the spectrum following electron capture in ¹⁶³Ho. The success of the ECHo experiment depends critically on the radiochemical purity of the ¹⁶³Ho sample, which is ion-implanted into the calorimeters. For this, a 30 kV high transmission magnetic mass separator equipped with a resonance ionization laser ion source is used. To meet the ECHo requirements, the ion source unit was optimized with respect to its thermal characteristics and material composition by means of the finite element method thermal-electric calculations and chemical equilibrium simulation using the Gibbs energy minimization method. The new setup provides an improved selectivity of laser ionization vs interfering surface ionization of 2700(500) and an overall efficiency of 41(5)% for the ion-implantation process.

Production and separation of 163Ho for nuclear physics experiments

This paper describes the production and chemical separation of the ¹⁶³Ho isotope that will be used in several nuclear physics experiments aiming at measuring the neutrino mass as well as the neutron cross section of the ¹⁶³Ho isotope. For this purpose, several batches of enriched ¹⁶²Er have been irradiated at the Institut Laue-Langevin high flux reactor to finally produce 6 mg or 100 MBq of the desired ¹⁶³Ho isotope. A portion of the Er/Ho mixture is then subjected to a sophisticated chemical separation involving ion exchange chromatography to isolate the Ho product from the Er target material. Before irradiation, a thorough analysis of the impurity content was performed and its implication on the produced nuclide inventory will be discussed.

Analysis of the 148Gd and 154Dy Content in Proton-Irradiated Lead Targets

This work presents the determination of the ¹⁴⁸Gd and ¹⁵⁴Dy content in Pb targets irradiated by 220-2600 MeV protons. It includes the chemical separation of lanthanides, followed by the preparation of proper samples, by molecular plating technique, for α-spectrometry measurements. The experimental cross section results were compared with theoretical predictions, calculated with the INCL++-ABLA07 code. The comparisons showed a satisfactory agreement for ¹⁴⁸Gd (less than within a factor two), while measured ¹⁵⁴Dy cross sections are higher than the theoretical values.

Production, separation and target preparation of 171Tm and 147Pm for neutron cross section measurements

The knowledge of the neutron capture cross sections of s-process branching point isotopes represents a basic requirement for the understanding of star evolution. Since such branching point isotopes are by definition radioactive, the measurement of their cross sections from thermal to stellar energies becomes a challenging task. Considerable amounts of material have to be produced, representing a significant radioactive hazard. We report here on the production and separation of 3.5 mg 171Tm from 240 mg 170Er2O3 and 72 μg 147Pm from 100 mg 146Nd2O3 irradiated at the ILL high flux reactor. Thin targets were prepared with high chemical and radioisotopic purity suitable for neutron capture measurements at n_TOF CERN and the SARAF-LiLiT facility.

Standardisation of the (129)I, (151)Sm and (166m)Ho activity concentration using the CIEMAT/NIST efficiency tracing method

The (129)I, (151)Sm and (166m)Ho standardisations using the CIEMAT/NIST efficiency tracing method, that have been carried out in the frame of the European Metrology Research Program project "Metrology for Radioactive Waste Management" are described. The radionuclide beta counting efficiencies were calculated using two computer codes CN2005 and MICELLE2. The sensitivity analysis of the code input parameters (ionization quenching factor, beta shape factor) on the calculated efficiencies was performed, and the results are discussed. The combined relative standard uncertainty of the standardisations of the (129)I, (151)Sm and (166m)Ho solutions were 0.4%, 0.5% and 0.4%, respectively. The stated precision obtained using the CIEMAT/NIST method is better than that previously reported in the literature obtained by the TDCR ((129)I), the 4πγ-NaI ((166m)Ho) counting or the CIEMAT/NIST method ((151)Sm).