Since our last information letter, we have experienced problems with the neutron guides. A guide is made of several elements (1.25m long) jointed together. Each element is a rectangular tube (internal section 25 * 150 mm2) the walls of which are 4 thick glass plates coated on one side with the reflecting layer. As neutrons must propagate in vacuum and, if like ours, the guides are not inside a housing, in steady state conditions the glass plates are permanently under an absolute pressure of
In the past we have already suffered few failures and we always managed to have some spare elements and to be able to repare immediately. This year, within a period of 6 months, we had 5 elements breaking on three different guides. The result is that some guides, and consequently the corresponding spectrometers has been out of work for a certa
Although the origin of these failures are not well understood, we planed to replace, as soon as possible, the elements which have been the most hardly irradiated insofar as they are probably those which have been the most weakened.