Development of a high precision electrostatic force balance for measuring quantity of dispensed fluid as a new calibration standard for the becquerel

Abstract

Abstract The 2019 redefinition of the kilogram not only changes the way mass is defined but also broadens the horizon for a direct realization of other standards. The true becquerel project at the national institute of standards and technology is creating a new paradigm for realization and dissemination of radionuclide activity. Standard reference materials for radioactivity are supplied as aqueous solutions of specific radionuclides which are characterized by massic activity in the units becquerel per gram of solution, Bq/g. The new method requires measuring the mass of a few milligrams of dispensed radionuclide liquid solution. An electrostatic force balance is used, due to its suitability for a milligram mass range. The goal is to measure the mass of dispensed fluid of 1 mg–5 mg with a relative uncertainty of less than 0.05%. A description of the balance operation is presented. Results of preliminary measurements with a reference mass indicate relative standard deviations less than 0.5% for tens of tests and differ 0.54% or less from an independent measurement of the reference mass.