Comment on 'Molecular arrangement in water: random but not quite'

Accurate high energy x-ray diffraction data are presented on liquid water measured at room temperature. Sources of both systematic and statistical errors within the experiment are considered and data consistency checks are discussed. It is found that the resulting x-ray pair distribution function is smoothly varying in real space and shows no evidence of small peaks in the 3-5???region. Our results are in contrast to the recent findings reported in Petkov et al 2012 J. Phys.: Condens. Matter 24 155102.     

Transmission‐mode diamond white‐beam position monitor at NSLS

Two transmission‐mode diamond X‐ray beam position monitors installed at National Synchrotron Light Source (NSLS) beamline X25 are described. Each diamond beam position monitor is constructed around two horizontally tiled electronic‐grade (p.p.b. nitrogen impurity) single‐crystal (001) CVD synthetic diamonds. The position, angle and flux of the white X‐ray beam can be monitored in real time with a position resolution of 500 nm in the horizontal direction and 100 nm in the vertical direction for a 3 mm × 1 mm beam. The first diamond beam position monitor has been in operation in the white beam for more than one year without any observable degradation in performance. The installation of a second, more compact, diamond beam position monitor followed about six months later, adding the ability to measure the angular trajectory of the photon beam.