Undergraduate Research at Jefferson Lab

Thermo-Mechanical Simulations for Positron Target

Student: Sohaib Bhatti

School: The Cooper Union for the Advancement of Science and Art

Mentored By: Andriy Ushakov and Joe Grames

Jefferson Lab plans to upgrade CEBAF to support a positron beam (project: Ce+BAF) for new experiments. Passing the electron beam through a high atomic number metal target generates bremsstrahlung, creating electron-positron pairs. Much of the energy carried in the electron beam is deposited into the target, creating thermal strains and stresses, potentially resulting in failure. To determine the lifetime of the target, a simulation framework to evaluate the structural integrity of the target was developed. FLUKA Monte Carlo simulations determined the energy deposited into the target, the results of which were imported into Ansys transient thermal simulation for temperature profiles. An Ansys Fluent CFD analyzed cooling loop efficiency in a two-way fluid-solid interaction. An Ansys structural simulation determined stress- strain effects and fatigue due to the pulse nature of the electron beam. The target is expected to last ~60 days in continuous operation. Experimental validation will prepare it for installation in CEBAF's positron injector, offering a polarized positron beam for scientists.