The Physics Impacts of Total Absorption Spectroscopy*

Total Absorption Spectroscopy (TAS) is a unique nuclear physics technique. But what is it? The total absorption in TAS refers to near 100% detector efficiency, with an emphasis on near 100% γ-ray detection. This very high γ-ray efficiency also leads to the detection of other particles emitted in β decay, such as βs and neutrons. TAS detector designs over the last 50 years have evolved from 2 face to face 5"x5" NaI detectors to modern TAS detectors that have from several hundred kilograms up to one ton of NaI. There are several groups in the USA and Europe that operate modern TAS detectors.

TAS detector designs trade energy precision for very high efficiency, enabling accurate measurement of the full β-decay intensity patterns. TAS detectors are also capable of measuring ground-state feeding directly at the same time as measuring the β feeding to excited levels.

Experimental TAS measurements impact a wide variety of physics, including nuclear-reactor physics such as decay heat and reactor antineutrino emission.  TAS measurements also impact astrophysical calculations of elemental abundances from the r- and p-processes. TAS measurements of  β-decay intensities together with (p,d) and (p,t) reactions are used as inputs to estimate (n,γ) reaction cross sections. Precise TAS measurements of exotic decay branches and accurate measurements of β-decay feeding patterns provide unique nuclear structure information. The first experiments at the Facility for Rare Isotopes (FRIB) were performed at the FRIB Decay Station Initiator (FDSi) with the TAS component aimed at the possible source of neutron star cooling via the Urca process. 

In this talk I will present a brief history of TAS, review the importance of various TAS design details, and discuss the impact of current and future TAS measurements on multiple areas of applied and fundamental physics research.