Self-healing photocathode device comprising a photoemissive multi-alkali semiconductor comprising a multi-alkali antimonide having the formula A.sub.xB.sub.y C.sub.zSb, where A, B and C are Group I alkali metals and x+y+z=3; a nanostructured porous membrane, one surface of which is in direct contact with the multi-alkali semiconductor and the opposing surface of which is disposed toward the inside of a sealed reservoir, such that the porous membrane and the sealed reservoir form a volume which is maintained at low pressure; a temperature control means in contact with the porous membrane, wherein the temperature control means regulates the temperature of the porous membrane at 200.degree. C. or less; a source comprising elemental cesium which is releasable into the enclosed volume; and, a current conducting means attached to the source.
STATEMENT OF FEDERAL RIGHTS
 The United States government has rights in this invention pursuant to Contract No. DE-AC52-06NA25396 between the United States Department of Energy and Los Alamos National Security, LLC for the operation of Los Alamos National Laboratory.