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Isolation of 163 Ho from dysprosium target material by HPLC for neutrino mass measurements

The rare earth isotope 163 Ho is of interest for neutrino mass measurements. This report describes the isolation of 163 Ho from a proton-irradiated dysprosium target and its purification. A Dy metal target was irradiated with 16 MeV protons for 10 h. After target dissolution, 163 Ho was separated from the bulk Dy via cation-exchange high performance liquid chromatography using 70 mmol dm –3 α-hydroxyisobutyric acid as the mobile phase. Subsequent purification of the collected Ho fraction was performed to remove the α-hydroxyisobutyrate chelating agent and to concentrate the Ho in a low ionic strength aqueous matrix. The final solution was characterized by MC-ICP-MS to determine the 163 Ho/ 165 Ho ratio, 163 Ho and the residual Dy content. The HPLC purification process resulted in a decontamination factor 1.4E5 for Dy. As a result, the isolated Ho fraction contained 24.8 ±1.3 ng of 163 Ho corresponding to holmium recovery of 72 ± 3%.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Nuclear Data Sheets for A = 163

The available data from the various reaction and decay studies leading to nuclides having mass number A=163 have been reviewed. These data are summarized and presented, together with adopted level schemes and properties, for nuclides from Eu (Z=63) through Os (Z=76). {sup 163}Eu represents a new addition to these nuclides. Level structures are now known for {sup 163}Ta and {sup 163}W through high-spin studies and recoil-decay tagging techniques. Several radioactive decays in this mass chain are not known at all or poorly established. No {beta} or {gamma}-ray data are available for {sup 163}Re-{sup 163}W-{sup 163}Ta-{sup 163}Hf {epsilon} decay chain. Those for {sup 163}Hf-{sup 163}Lu-{sup 163}Yb {epsilon} decay chain and {sup 163}Eu-{sup 163}Gd-{sup 163}Tb {beta}{sup -} decay chain are very sketchy. This evaluation is an update and revision of the previous one (2000Si01)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Captures of hot and warm sterile antineutrino dark matter on EC-decaying {sup 63}Ho nuclei

Capturing low-energy electron antineutrinos on radioactive {sup 163}Ho nuclei, which decay into {sup 163}Dy via electron capture (EC), is a noteworthy opportunity to detect relic sterile antineutrinos. Such hypothetical particles are more or less implied by current experimental and cosmological data, and they might be a part of hot dark matter or a candidate for warm dark matter in the Universe. Using the isotope {sup 163}Ho as a target and assuming reasonable active-sterile antineutrino mixing angles, we calculate the capture rate of relic electron antineutrinos against the corresponding EC-decay background in the presence of sterile antineutrinos at the sub-eV or keV mass scale. We show that the signature of hot or warm sterile antineutrino dark matter should in principle be observable, provided the target is big enough and the energy resolution is good enough.

79 ASTRONOMY AND ASTROPHYSICS↗