The journey of Modular Total Absorption Spectrometer from ORNL via ANL to FRIB.

The ORNL’s Modular Total Absorption Spectrometer (MTAS) was born in 2009 following the American Recovery and Reinvestment Act funding, with the goals to improve our knowledge on the decay heat and anti-neutrino emission from nuclear reactors while also informing the nuclear structure of fission products. MTAS is the largest and most efficient total absorption spectrometer in the world with about 1 ton of active NaI(Tl). MTAS has a unique 19-module hexagonal construction, now upgraded to 24 segments. MTAS is shielded with 6 tons of lead against background gamma radiation as a mix of lead plates and SWX foam.

MTAS was operated at ORNL in 2012 -2016. It was moved to the CARIBU facility at ANL in 2018. MTAS experiments at CARIBU profited from beams of 252Cf fission fragments purified with the use of the high-resolution separator and Multi-Reflection Time-of-Flight device.

We moved MTAS from ANL to FRIB in 2021. In June 2022 first MTAS experiment has been performed at FRIB Decay Station initiator with the high energy fragments of 82Se beam implanted into a position sensitive YSO scintillator developed at UTK. The construction and complex operations related to the journeys of MTAS between ORNL, ANL and FRIB will be presented.