In:
Scientific Reports, Springer Science and Business Media LLC, Vol. 13, No. 1 ( 2023-03-08)
Abstract:
We have grown $$^{232}$$ 232 Th:CaF $$_2$$ 2 and $$^{229}$$ 229 Th:CaF $$_2$$ 2 single crystals for investigations on the VUV laser-accessible first nuclear excited state of $$^{229}$$ 229 Th, with the aim of building a solid-state nuclear clock. To reach high doping concentrations despite the extreme scarcity (and radioactivity) of $$^{229}$$ 229 Th, we have scaled down the crystal volume by a factor 100 compared to established commercial or scientific growth processes. We use the vertical gradient freeze method on 3.2 mm diameter seed single crystals with a 2 mm drilled pocket, filled with a co-precipitated CaF $$_2$$ 2 :ThF $$_4$$ 4 :PbF $$_2$$ 2 powder in order to grow single crystals. Concentrations of $$4\cdot 10^{19}$$ 4 · 10 19 cm $$^{-3}$$ - 3 have been realized with $$^{232}$$ 232 Th with good ( 〉 10%) VUV transmission. However, the intrinsic radioactivity of $$^{229}$$ 229 Th drives radio-induced dissociation during growth and radiation damage after solidification. Both lead to a degradation of VUV transmission, currently limiting the $$^{229}$$ 229 Th concentration to $$ 〈 5\times 10^{17}$$ 〈 5 × 10 17 cm $$^{-3}$$ - 3 .
Type of Medium:
Online Resource
ISSN:
2045-2322
DOI:
10.1038/s41598-023-31045-5
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2023
detail.hit.zdb_id:
2615211-3
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