title: Migration to new ampoule types for the NPL secondary standard ionisation chambers.
abstract: As the pre-calibrated sample containers used for activity assay in the two NPL secondary standards ionisation chambers are being phased out, suitable replacements have been identified. Characterisation checks have been carried out on the new ISO ampoules and a long-term recalibration schedule has been devised. Around 40 calibration factors have been determined so far and comparison of ion chamber responses for the two ampoule types showed variations of up to 7% for low energy photon emitting radionuclides.
authors.affiliation: National Physical Laboratory, Teddington, Middlesex TW110LW, UK.
authors.forename: M
authors.initials: M
authors.lastname: Baker
authors.affiliation: National Physical Laboratory, Teddington, Middlesex TW110LW, UK.
authors.forename: A
authors.initials: A
authors.lastname: Fenwick
authors.affiliation: National Physical Laboratory, Teddington, Middlesex TW110LW, UK.
authors.forename: K
authors.initials: K
authors.lastname: Ferreira
authors.affiliation: National Physical Laboratory, Teddington, Middlesex TW110LW, UK. Electronic address: john.keightley@npl.co.uk.
authors.forename: J
authors.initials: J
authors.lastname: Keightley
authors.affiliation: National Physical Laboratory, Teddington, Middlesex TW110LW, UK.
authors.forename: L
authors.initials: L
authors.lastname: Johansson
authors.affiliation: National Physical Laboratory, Teddington, Middlesex TW110LW, UK.
authors.forename: S
authors.initials: S
authors.lastname: Collins
keywords: BS ampoules; Calibration factors; ISO ampoules; Ionisation chambers response