A NEW ACCELERATOR MASS SPECTROMETER FOR TRACE ELEMENT ANALYSIS AT THE NAVAL RESEARCH LABORATORY

Abstract A new accelerator mass spectrometer (AMS) facility is under construction at the Naval Research Laboratory for trace element analysis of electronic, biological, and geological materials. The design provides for parallel mass analysis over a broad mass range for conducting and insulating samples, and offers 10 μm lateral image resolution, depth profiling, and sensitivity down to tens of ppt of trace impurities. The facility will use a modified commercial secondary ion mass spectrometer as the source of secondary ions. A Pretzel magnet will act as a unique recombinator to simultaneously transmit from 1 to 200 amu ions, but attenuate intense matrix-related beams. After acceleration, a single charge state will be selected by a 3° electrostatic bend, then the selected ions will be energy analyzed by a 2.2 m radius, 30° spherical electrostatic analyzer ( E ΔE ≈ 800 ). Finally, a split pole mass spectrograph with a 1.5 m long focal plane will provide parallel analysis over a broad mass range ( M max M min ≈ 8 ) with high mass resolution ( M ΔM ≈ 2500 ).