The feasibility of generating a single attosecond x-ray pulse is demon
strated. This can be achieved by generating high-order harmonics of a
light pulse with a variable ellipticity and a relative spectral width
Delta omega/omega approximate to 0.04, A way is proposed for generatin
g such a pulse by linear optical methods from a linearly polarised ban
dwidth-limited laser pulse. An attosecond x-ray pulse generated from s
uch a laser pulse may then be separated in the far-field diffraction z
one from the overall field by a system of apertures.