Hi Ron and all, I realize that I'm not the only one who'd like to use the Gandolfi technique without the need to make one's own photographic films.
In principle there are various ways to solve the problem. One would be to mount a Gandolfi attachment on a 4-circle goniometer equipped with a CCD area detector. We spent some time into this, and recognized various problems: the angular resolution of such instruments is low for powder diffraction purposes, and both background and intensities show weird variations along 2theta. This is mainly because several frames have to be combined to give the "full" pattern (similar to the 5*5 cm setup you thought about). Another way would be to substitute the film with an imaging plate. Here one gets the full pattern, but resolution is still a concern. Once IPs (and scanners) with a resolution of 20 µm or better will be available, it should be worth wile to follow this approach. The IP might of course be cut to comply with the traditional 35 mm film strip but, at this point, a more interesting solution would be the use of increased axial height in order to minimize the limits of the Gandolfi technique (see J Appl Cryst 1994 27:855). Please tell me if you are interested in such solutions, best Miguel Hi everyone, Not really a Rietveld question but I thought this group would be good to ask... As a mineralogist we have used Gandolfi cameras in the past to identify small amounts of unknown mineral mixtures. The camera mechanism randomizes the orientation of the small single crystal or crystal aggregate to generate a debye-scherrer pattern. (usually in a 57mm camera) this was a low tech inexpensive method that would run off a normal lab Xray source. Film is no longer available. I thought about adapting a flat plate detector and the mechanism I have from a gandolfi camera to be able to do these exposures. With the market now for digital Xray detectors for health and industrial testing I thought maybe the cost of a small 5cm x 5cm detector might make this possible. The problem as I see it is that these detectors take advantage of W xrays and are not sensitive to the softer Cu or Mo Xrays. I see some have Be coverings for when they are doing real time radiographs. Does anyone have any advice or details on sourcing inexpensive detectors such as this. Only rough estimates intensities are required as most of the information that is required is position of the lines. I know there are more expensive microdiffractometer systems that will do this but am looking for low cost solution so that we can study a large number of fragments in a routine fashion. Thanks very much in advance for any suggestions ~Ron ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Please do NOT attach files to the whole list <alan.he...@neutronoptics.com> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -- Miguel Gregorkiewitz Dip Scienze Fisiche, della Terra e dell'Ambiente, Università via Laterina 8, I-53100 Siena, Europe fon +39'0577'233810 fax 233938 email gre...@unisi.it
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Please do NOT attach files to the whole list <alan.he...@neutronoptics.com> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
