Multi-foil activation analysis to measure SPARC fusion energy and neutron energy spectra*

In this poster, we explore the Multi-Foil Activation system for the SPARC tokamak. Activation foils are an in-vessel neutron diagnostic technique capable of withstanding the violent conditions near the plasma. We will assess the performance of various activation foil materials (such as Al, In, Fe, Cu, etc.) for the fusion energy measurement of the upcoming SPARC tokamak [1]. Through OpenMC [2] and FISPACT [3] simulations and irradiation experiments with Deuterium-Tritium & Deuterium-Deuterium neutron generators, we will down-select to a few suitable foils to use for SPARC and develop a rapid and accurate multi-foil measurement protocol. We also need to pair the multi-foil set with an appropriate capsule which will not interfere excessively with the measurement. To achieve this, we will first characterize a High Purity Germanium Spectrometer (HPGe), and thereafter test various foil and capsule combinations. We will pursue spectrum unfolding on the gamma decay energy spectra from the irradiated multi-foil set in order to deduce the fusion energy yield, neutron energy spectra, and DT fuel ion ratio; this ultimately allows us to peer into the reaction, something necessary for SPARC to serve its purpose as a research device.

[1] Creely AJ, Greenwald MJ, Ballinger SB, et al. Overview of the SPARC tokamak. Journal of Plasma Physics.

[2] Paul K. Romano, Ann. Nucl. Energy, 82, 90–97 (2015)

[3] J-Ch. Sublet,  “Nuclear Data Sheets 139 (2017)