Thermal Design and Experimental Validation of a Water-Cooled Bimetallic Minichannel Beam Dump for High-Power Heavy-Ion Accelerators

Abstract

Efficient thermal management of beam-intercepting devices is essential for high-power heavy-ion accelerators,where intense and localized energy deposition can limit primary beam power and operational reliability. This work presents the thermal design and experimental validation of a water-cooled bimetallic minichannel beam dump developed for the Facility for Rare Isotope Beams (FRIB), a leading experimental nuclear physics facility. The design integrates three key thermal features: a tilted absorber geometry to reduce local heat flux, a CuCrZr/Al2219 bimetallic structure to enhance heat spreading while maintaining water-side compatibility, and 2-mm-wide minichannels to achieve high convective heat removal. A conjugate thermal model was developed to predict surface temperature, internal temperature gradients, bimetallic-interface temperature, coolant temperature rise, and thermal margin under representative beam-loading conditions. The prototype was validated in vacuum ($\approx$5$\times 10^{-4}$ torr) using a 17-keV electron beam. Surface temperatures were measured by infrared thermography, and internal temperatures were measured using embedded thermocouples. The calculated surface temperature distributions were generally consistent with the measurements within the experimental uncertainty of 4$\%$ in absolute temperature for central beam irradiation, while internal temperature measurements showed reasonable agreement within 15$\%$, mainly due to uncertainties in thermocouple placement and beam-position calibration. The validated model confirms that the minichannel beam dump can maintain absorber temperatures within the design limit under intermediate-power FRIB operating conditions. These results demonstrate the effectiveness of bimetallic minichannel cooling for compact, high-heat-flux beam dump systems in heavy-ion accelerator facilities.