Status report: The first three years of MICADAS operation at AEL-AMS National Facility, Ottawa, Canada

Abstract The André E. Lalonde National Facility for Accelerator Mass Spectrometry (AEL-AMS) at the University of Ottawa has been operational since 2014, utilizing High Voltage Engineering (HVE) 3MV and MIni CArbon DAting System (MICADAS) AMS systems. To date, the laboratory has processed over 30,000 graphite targets for high-quality radiocarbon ( 14 C) analysis for users from Canada and internationally. Sample matrices include diverse organic materials, inorganic solids, dissolved inorganic and organic carbon (DIC/DOC) in surface waters and groundwater, and carbon dioxide (CO 2 ) and methane (CH 4 ) in gas mixtures. In 2021, a dedicated 14 C AMS system (MICADAS #33, Ionplus AG) was added to meet the growing demand for radiocarbon analysis. This report reviews recent updates to sample processing protocols, focusing on Quality Assurance/Quality Control (QA/QC) performance of the first three years of MICADAS operation. Routine procedures such as acid-alkali-acid (AAA) and direct combustion yield low procedural blanks (F 14 C avg = 0.0022, σ = 0.0006). Refinements to bone collagen extraction protocols have improved yield and reduced blanks (F 14 C avg from 0.0040 to 0.0025). While some methods remain inherently prone to higher blanks (i.e., DOC wet oxidation), our blanks remain low (F¹⁴C avg < 0.0042) and consistent (σ < 30%). Graphite targets in the range of 400 to 1300 µg C are routinely measured. Planned developments are reviewed, including pre-screening of samples with a Fourier Transform Infrared Spectrometer (FTIR), automation of sample preparation, database development, and diversification into smaller sample measurements via graphite (<400 µg C) and samples appropriate for gas ion source assays (<200 µg C).