Abstract: An evaporator for a capillary pumped loop, has: (a) a tubular wick for containing coolant liquid centrally therein, the body of the wick being saturated with the liquid coolant; (b) a tubular heat exchanger for receiving said wick; and (c) one or more longitudinal vapor channels between said wick and said heat exchanger, for transporting a vapor of the working liquid out of the evaporator; where this tubular wick comprises a porous organic/inorganic composite made by the sol-gel process. By replacing the conventional polyethylene wick with the composite wick, smaller pores, greater porosity, greater thermal stability, and other advantages are secured.