SUPERSONIC PROPAGATION OF AN IONIZATION FRONT IN LOW-DENSITY FOAM TARGETS DRIVEN BY THERMAL-RADIATION - AFSHARRAD,T; DESSELBERGER,M; DUNNE,M; EDWARDS,J; FOSTER,JM; HOARTY,D; JONES,MW; ROSE,SJ; ROSEN,PA; TAYLOR,R; WILLI,O (PHYSICAL REVIEW LETTERS, 1994)