X-ray diffraction based crystal centering method using an active pixel array sensor in rolling shutter mode

A method of precisely centering a crystal sample in the X-ray beam of an X-ray diffractometer, the method comprising:

• a) mounting the sample in the diffractometer and determining an approximate center of the sample through which three perpendicular sample axes pass;
• b) positioning the sample outside of the X-ray beam such that a first of the sample axes is perpendicular to a center axis of the X-ray beam;
• c) moving the sample toward the X-ray beam along the first axis;
• d) detecting the presence of diffraction spots using an active pixel array sensor operating in rolling shutter mode when the sample enters the X-ray beam, and determining the position of the sample when said diffraction spots first appear;
• e) detecting the absence of diffraction spots using said detector when the sample exits the X-ray beam, and determining the position of the sample when said diffraction spots first disappear;
• and
• f) repeating steps b) through e) for each of the other two sample axes.