Performance of the HVE 5MV AMS system at CEREGE using an absorber foil for isobar suppression

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 2008-04, Vol.266 (8), p.1828-1832
• Main Authors: Klein, M.G., Gottdang, A., Mous, D.J.W., Bourlès, D.L., Arnold, M., Hamelin, B., Aumaître, G., Braucher, R., Merchel, S., Chauvet, F.
• Format: Article
• Language: English
• Subjects: 36Cl; AMS; Isobar suppression
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/j.nimb.2007.11.077

At CEREGE (Aix-en-Provence, France) a HVE 5MV AMS facility has been put in operation for measuring the long-lived cosmogenic radioisotopes 10Be, 26Al, 36Cl, 41Ca and 129I. Characteristic to the AMS system is that isobaric background can be suppressed by means of the nuclear-charge dependent energy loss in an absorber foil and subsequent energy selection by an electrostatic deflector. In case of 36Cl analysis, this method suppresses 36S by a factor of at least 200. As a consequence, high source output does not overload the detector by isobaric interference. Together with the high-resolution gas ionisation detector 36Cl measurements at an energy as low as 30MeV are supported. This can be readily achieved by gas stripping at 5MV terminal voltage, thereby avoiding the use of cumbersome foil stripping. The performance of the AMS system is reviewed. 36Cl/Cl ratios down to 4×10−16 have been measured.