Note: Thickness determination of freestanding ultra-thin foils using a table top laboratory extreme ultraviolet source.

We present a versatile and handy method allowing a thickness determination of freestanding thin plastic foils by its transmission characteristics in the extreme ultraviolet (EUV) spectrum. The method is based on a laser induced plasma source, emitting light in the EUV region, a compact double-mirror EUV monochromator operating at a fixed wavelength of 18.9 nm, and a CCD camera. The measurement delivers transmission values with a standard deviation of ΔT = 0.005 enabling foils thickness characterization with nm-accuracy at a given foil density and stoichiometric composition. Well characterized freestanding ultra-thin foils can be directly implemented in, e.g., high intensity laser matter experiments without further manipulation.