纺织服装机械网

The wet film technique of the old HUBER Guinier Camera 621 has been replaced by an up-to-date detection system involving amodern imaging plate. F igital X-ray powder diffraction intensity data have been achieved by the use of a single channel step scan scintillation detector. Now, these data are available within a couple of minutes instead of hours, because of the time multiplex effect of the position sensitive imaging plate method. The camera housing contains the complete read out unit including laser scanner, signal preamplifier, and erasure lamp.This instrument combines the high resolution of the old wet film technique with the extreme fast sensitivity of the imaging plate process giving the digital intensity data of the Guinier powder diffractogram, ready for Rietveld analysis.That imaging plate method supersedes even the position sensitive proportional detector technique. This is because of the relative small focal circle diameter of 180 mm, which cannot be met by a proportional PSD. The 670 package includes the hard- and software required for the control of the data collection. A maximum of 20001 data points per scan can be stored into most of the common data file formats, compatible to any crystallographic evaluation software.The Imaging Plate is a flexible image sensor in which bunches of very small crystals (grain size: about 0.005 mm) of photostimulable phosphor of barium fluorobromide containing a trace amount of bivalent europium as a luminescence center, formulated as BaFBr: Eu2+, are uniformly coated on a polyester support film.

Exposure of X-ray powder diffraction radiation to the imaging plate isperformed in a manner similar to that of the wet negative film.The exposed imaging plate is scanned with a focused red laser beam. Theblue photostimulated lumines-cence (PSL) released by the laser is collected into a photomultiplier tube (PMT). Its analog output signals are converted todigital signals by a 16 bit A/D converter.The imaging plate is reusable after erasing the residual latent diffractogramwith uniformly irradiated visible white light.