Microchannel cooling for a high-energy particle transmission window, an RF transmission window, and VLSI heat dissipation

The transmission of energetic particles from vacuum to atmospheric pressure through a window results in some energy deposition within the window. This energy heats the window, increases its temperature, reduces its mechanical strength, and so limits the particle flux through the window. An analysis of heat transport indicates that a transmission window that incorporates microchannel cooling within the window can increase its heat dissipation, thereby increasing beam flux by several orders of magnitude. This increase occurs because the convective heat-transfer coefficient can increase to /spl sim/1 MW/m/sup 2//spl times/K for fully developed turbulence in 131 /spl mu/m diameter capillary tubing. Mechanical and thermal constraints are discussed, as well as the hydraulic system necessary to achieve appropriate fluid flow. Experimental heat dissipation using 131 /spl mu/m capillary tubes in a seven-tube manifold implies that a 5 cm diameter foil window could dissipate 2.7 kW/cm/sup 2/ continuously. Design examples include a 30 mA/cm/sup 2/ electron-beam window, a 722 W/cm/sup 2/ RF window, and 950 W/cm/sup 2/ very large scale integration (VLSI) cooling.