Estimates of signals in LCLS diffraction imaging experiments

Chapman, H N

Lawrence Livermore National Laboratory

关键词: Photons;    X-Ray Diffraction;    Diffraction;    59 Basic Biological Sciences;    Sampling;   

DOI  :  10.2172/15015863
RP-ID  :  UCRL-TR-210230
RP-ID  :  W-7405-ENG-48
RP-ID  :  15015863

美国|英语

来源: UNT Digital Library

【 摘 要 】

In the coherent X-ray diffraction imaging experiments, samples will be injected or placed in the beam and a two-dimensional diffraction pattern will be collected for a single pulse. This is repeated for a large number of pulses, with the data being read out of the detector each pulse, and stored if the data meets a requirement of enough total recorded counts. There must be sufficient pixels in the detector to over-sample the diffraction pattern, which depends on the sample size and desired resolution, as described below. The scattering from the sample covers a large dynamic range: it is strong very close to the central core and at high angles there will be much less than one photon per pixel. Since the technique relies upon classifying and averaging a large number of patterns, the read noise must be considerably less than the photon count per pixel averaged over these patterns. Estimates of the noise level and dynamic range are given below, after first listing the requirements of pixel count and sampling.