In the French Simulation Program, poly(alpha-methylstyrene) (PAMS) microshells serve as mandrels for capsules used within inertial confinement fusion targets on the LMJ (Laser MégaJoule). Controlled double emulsions are employed to produce micrometer- to millimeter-sized water-in-oil-in-water emulsions, which are subsequently dried and emptied to solidify the mandrels while avoiding surface or sphericity defects. This work evaluates two injection systems, mechanical and pressure-driven, for the production of triphasic emulsions. The pressure-driven system demonstrated superior control over flow dispersions across all three injected phases, offering enhanced injection monitoring and early detection of anomalies. Optical measurements of dried PAMS mandrels with a common diameter of 1900 µm, often used in laser experiments, revealed significantly improved characteristics when produced using the pressure-driven system. These improvements included reduced standard deviation and narrower diameter ranges.