title: Measurement of the 226Th and 222Ra half-lives.
abstract: The half-lives of (226)Th and (222)Ra were measured by counting alpha-particle emissions from sources as a function of time. The (226)Th sources were prepared from an open (230)U source, capturing recoil atoms after alpha-particle decay on glass disks or even directly onto a detector. Similarly, the (222)Ra sources were obtained by self-transfer of recoil atoms from (226)Th sources. The activity measurements were performed in (nearly-)2π geometry with an ion-implanted silicon detector. The decay curves were analysed in different ways, incl. moment analysis, trying to avoid the pitfalls of bias of least-squares fits to Poisson distributed data. The observed half-life values are T(1/2)((226)Th)=30.70 (3) min and T(1/2)((222)Ra)=33.6 (4) s. Literature values show some inconsistency.
authors.affiliation: European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel, Belgium. stefaan.pomme@ec.europa.eu
authors.forename: S
authors.initials: S
authors.lastname: Pommé
authors.forename: G
authors.initials: G
authors.lastname: Suliman
authors.forename: M
authors.initials: M
authors.lastname: Marouli
authors.forename: R
authors.initials: R
authors.lastname: Van Ammel
authors.forename: V
authors.initials: V
authors.lastname: Jobbágy
authors.forename: J
authors.initials: J
authors.lastname: Paepen
authors.forename: H
authors.initials: H
authors.lastname: Stroh
authors.forename: C
authors.initials: C
authors.lastname: Apostolidis
authors.forename: K
authors.initials: K
authors.lastname: Abbas
authors.forename: A
authors.initials: A
authors.lastname: Morgenstern
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D006207:Half-Life; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation*; D011883:Radium / Q000032:analysis / Q000737:chemistry*; D013910:Thorium / Q000032:analysis / Q000737:chemistry*
chemical_list: D013910:Thorium; D011883:Radium