Current status of MALT AMS facility: A report of updated performance and recent achievement

Abstract Current status of MALT (Micro Analysis Laboratory, Tandem accelerator, The University of Tokyo) and recent achievements both in development and application are reported. Multi-nuclide AMS (10Be, 14C, 26Al, 36Cl, 129I) system is available and shows good performance as well as PIXE, NRA, ERDA/RBS systems. 236U-AMS system was developed and the background of 236U/238U = 3 × 10−10 was so far achieved. A test bench beam line for Laser Photo Detachment was also constructed for the development of the future isobar separation technique. Among various application fields using AMS, the study of iodine isotope system, both natural and anthropogenic, has been the most energetically promoting research field at MALT in recent years. We proposed natural equilibrium isotopic ratio 129I/127I as 2.0 × 10−13 in marine environment. We also contributed to reconstruction of initial 131I deposition distribution due to the Fukushima Daiichi Nuclear Power Plant accident.