Performance of the rebuilt SUERC single-stage accelerator mass spectrometer

Richard P Shanks,Philippa L Ascough,Andrew Dougans,Paul Gallacher,Pauline Gulliver,Dylan H Rood,Sheng Xu,Stewart P.H.T Freeman

doi:10.1016/j.nimb.2015.07.122

Abstract

The SUERC bipolar single-stage accelerator mass spectrometer (SSAMS) has been dismantled and rebuilt to accommodate an additional rotatable pre-accelerator electrostatic spherical analyser (ESA) and a second ion source injector. This is for the attachment of an experimental positive-ion electron cyclotron resonance (ECR) ion source in addition to a Cs-sputter source. The ESA significantly suppresses oxygen interference to radiocarbon detection, and remaining measurement interference is now thought to be from 13C injected as 13CH molecule scattering off the plates of a second original pre-detector ESA.

Highlights

The NEC single-stage accelerator mass spectrometer (SSAMS) is a popular model accelerator mass spectrometer for radiocarbon measurement
Straggled reduced-energy 16O from either ion source could be injected along with the 14C, as could 13C as full energy 13CH. Measurements in both polarities suffer from an interference to the 14C particle signal which is centred when the pre-detector electrostatic spherical analyser (ESA) is reduced by $300 V from the 19.8 kV ESA tune for 290.4 keV 14C
The beam from either ion source is injected into the accelerator by a 90° magnet with a fast electrostatic manifold bouncing system (MBS)

Summary

Introduction

The NEC single-stage accelerator mass spectrometer (SSAMS) is a popular model accelerator mass spectrometer for radiocarbon measurement. All such instruments must resolve 14C atoms from abundant interferences. Straggled reduced-energy 16O from either ion source could be injected along with the 14C, as could 13C as full energy 13CH Measurements in both polarities suffer from an interference to the 14C particle signal which is centred when the pre-detector electrostatic spherical analyser (ESA) is reduced by $300 V from the 19.8 kV ESA tune for 290.4 keV 14C. We have added a switchable pre-accelerator ESA to both facilitate rapid ion source change for the positive-ion experimentation, and to filter ion energy to address the interferences

Rebuild

Remaining interference

Background

Discussion

Findings

Conclusion