Monte Carlo simulations of primary spectrometer of IN13. Effects of the characteristics of the H24 neutron guide. A project for a focalizing guides at the beginning of IN13

Starting from 2001 a progressive upgrade of IN13 is planned in order to improve the incident flux and give to the instrument a certain versatility. At the present, low flux is the big limit in the performance of the instrument, so it is our priority. Simulations of the different part of the instrument as well as of the guide H24 have been very helpful in order to check the different modifications envisaged, verify our ideas and to determine which are the most promising modifications and the possible degradation of certain characteristics of the instrument. This a particularly important point, as one has to preserve the characteristics that make of IN13 a particularly suited spectrometer for the study of the local dynamics of soft matter, such as polymers and biological systems, e.g. a large momentum transfer range (now 0.3<Q(Å-1)<5.5) and an energy resolution of few µeV. This report presents the results of the ray tracing Monte Carlo simulations of the neutron guides and of the primary spectrometer of IN13 and the study of the consequences of the changes of the neutron guides proposed by the ILL staff on the characteristic of the neutron beam at the sample position. Furthermore a project for a focalizing guide before IN13's monochromator will be presented