UC San Diego

The next-generation neutron spallation target station, the Target-Moderator-Reflector System (TMRS) Mk. IV, is to be installed in 2020. This iteration features an unprecedented, water-cooled, third internal target aptly named the Upper Target and designed completely by analysis. An empirical investigation in the form of this thesis was undertaken to assess target conformance to the computational results which deemed the incorporated cooling adequate. Three facets of the

target housing were designated for verification: displacement under hydraulic loading, critical fluid velocities, and the characteristic heat transfer coefficient.

With the potential for flow maldistribution under excessive displacements, static pressure testing of a procured Upper Target prototype housing was performed. Discrepancies of an order of magnitude became evident between empirical and simulated displacements, leading to uncertainty in both cooling capacity due to altered geometry and structural integrity.

A closed water flow loop reproducing the flow parameters intrinsic to the TMRS Mk. IV was constructed. Utilizing a high-speed camera and a transparent Upper Target mock-up, global fluid dynamics were observed analogous to computer simulation. Furthermore, crucial velocities such as exist at the point of beam impingement were met or exceeded, thus implicitly satisfying cooling requirements.

Finally, in simulating the beam heating profile and peak heat flux via induction heating, the local heat transfer coefficient was confirmed sufficiently for mitigating nucleate/flow boiling. Collectively, this investigation demonstrates the validity of the cooling design even considering the unforeseen deflections, notwithstanding the structural implications.