An innovative lightweight thermal management concept providing high heat flux capability for High Power Microwave (HPM) beam collectors or beam dumps for Directed Energy Weapon Systems is proposed. Major obstacles to the practical application of DE Weapons for aircraft require effective solutions in thermal management and reducing the mass of the components. The beam collector/dump handles the majority of the thermal load and represents a major thermal management challenge. The proposed thermal approach utilizes enhanced cooling mechanisms (subcooled nucleate flow boiling and jet-impingement cooling) coupled with advanced high thermal conductivity materials and optimized cooling channel geometry. The concept provides both improved thermal performance and reduces the beam collector mass by 30-50 per cent over current designs. The enhanced heat transfer and lower temperature gradients through the structure (due to improved thermal conductivity and thinner walls) allows much higher heat flux operation yet maintains the collector's structural temperatures. The overall design concept provides a mass efficient and highly effective thermal control approach that can be fully integrated with the aircraft cooling system.The lightweight and high heat flux structure will have immediate application for HPM and High Energy Laser (HEL) Directed Energy Weapon Systems. High system payoffs include higher heat flux operation, reduced component mass, lower temperatures and improved structural integrity of the components. The technology can be applied to other high heat flux applications including: power devices, advanced avionics, electric vehicles and high performance super computers.