We describe the properties of the exploding foil neon-like germanium s
oft X-ray lasers having wavelengths of 19-28 nm and gain length produc
t of more than 10. The measured X-ray intensity of lasing lines from a
n exploding foil target has been explained with the results of the pla
sma hydrodynamic code from the viewpoint of suitable condition of elec
tron density and temperature for creating population inversion.