High-pass photocathode x-ray ionization chamber for surface EXAFS

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Abstract
An x-ray detector that collects electrons emitted from a cathode plate and amplifies them through field intensified ionization in helium gas is described. The sensitivity of the detector to the photon frequency increases by nearly an order of magnitude as the photon energy exceeds the absorption edge of the photocathode. The detector current as a function of the x-ray frequency is shown to yield the extended x-ray absorption fine structure (EXAFS) of layers of copper as thin as 30 A in a few minutes.