A fast bouncing system for the high-energy end of AMS

Drifts in the accelerator stability as well as those in beam transport comp onents are the main limitations in achieving high precision in accelerator mass spectrometry (AMS). In order to achieve the high precision required fo r isotopic geology and geochronology applications, the sequence of isotopes of interest should be counted for as short an interval as possible. While fast isotope switching can be achieved readily at the low-energy end, it ha s hitherto not been possible to do so at the high-energy end. For a narrow range of transmission typical for most analysing magnets, fast switching (< 1 ms) of the field is not possible if steady state is also desired. We have devised a novel electric means to modulate the beam trajectory in a static magnetic field for the AUSTRALIS (AMS for ultra sensitive trace element an d isotopic studies) system, recently developed at the HIAF laboratory. The system is based on a pair of deflector plate sets, deflecting in the orbit plane, at the entrance and exit of the high-energy analysing magnet. Origin ally designed as energy modulator, the principle readily adapts as an isoto pe switcher. With switching time <10 ms/isotope, better than 1 permil has b een achieved in Pb isotope ratio measurements. (C) 2000 Elsevier Science B. V. All rights reserved.