X-ray reflectometer

Apparatus for detecting radiation, comprising:

• a stage, which is adapted to hold a sample;
• a radiation source, which is adapted to irradiate the sample with X-rays;
• an array of detector elements, positioned to receive the X-rays reflected from the sample over a range of angles and to generate charges responsive thereto, the array including a first element and a last element, such that the first element receives the radiation reflected from the sample in a lower portion of the range of angles relative to a plane of the sample, and the last element receives the radiation reflected from the sample in a higher portion of the range of angles relative to the plane of the sample, the array having a length defined by a distance between the first and last elements;
• an evacuable enclosure having a front side and a rear side separated by a distance that is at least equal to the length of the array, wherein the array is positioned at the rear side of the enclosure, and the enclosure comprises a window at a front side thereof, which is adapted to allow the radiation to pass therethrough so as to impinge on the array;
• a readout circuit;
• and
• a shift register, which has an output connected to the readout circuit and is coupled to transfer the charges generated by the detector elements from the detector elements to the output in sequence along the array beginning with the last element.