ASTER report status and upgrades.
M. Karim Keddadouche1, Dr Régis Braucher1, Mr. Georges Aumaître1, Dr. Vincent Godard1
1CEREGE, CNRS, Collège de France, IRD, INRAE, Aix Marseille Univ., Aix-en-Provence, France
ASTER (CEREGE, Aix en Provence, France) is a HVEE 5MV AMS in operation since 2007 within the LN2C (Laboratoire National de Nucléides Cosmogéniques, French national facility for cosmogenic nuclides). ASTER measures in routine around five thousand samples per year dispatched between ¹⁰Be, ³⁶Cl and ²⁶Al. Initially delivered with the HVEE SO-110B, ASTER has been upgraded in 2016 with the SO-110-C head source slightly increasing the output currents for ²⁷Al- and ⁹BeO-. This source is now used for all ¹⁰Be and ²⁶Al measurements while the previous source is dedicated to ³⁶Cl. We will present several tests and performances of the SO-110-C and how it is operated to ensure high quality routine measurements (high level and stable current) with a minimum cleaning procedure.
In December 2019, a new line incorporating a gas-filled magnet was installed. Despite the progress made by the new source, this upgrade will be used to further improve the overall efficiency of ²⁶Al measurements by producing at least an order of magnitude higher negative ion beam in the ion source by injecting AlO- rather than Al-. Since the isobaric interfering MgO- is also produced, separation of these isobars becomes imperative. This new beamline thus endowed a multi-anode gas ionization chamber (GIC) and a 120 degrees (450 mm radius) gas-filled magnet (GFM) to reduce the initial intensity of Mg combined to realize this preliminary test. Due to the pandemic situation this extension is still under development but preliminary tests will be presented.
We would like to dedicate this work to our late colleague and friend Didier Bourlès († 26/04/1955 – 01/03/2021).
GENERAL RESEARCH INTERESTS: Developments and applications of cosmogenic nuclides in geosciences. Quantification of landscape processes.
My research interests focus on applying cosmogenic nuclides to the quantification of the various processes (tectonics, climate, …) affecting and modelling the Earth’s surface over the last few millions years. To do so, I am working on improving our knowledge of the production mechanisms for commonly used cosmogenic nuclides such as 10Be,26Al,36Cl. I have also developed the depth profile approach allowing the direct determination of both exposure age and denudation rate affecting the studied surface.
Since June 2020, co director of LN2C/ASTER facilities.