It is the aim of the present thesis to develop a new monochromator based on silicon crystals for NFS at the resonance of 121 Sb. The monochromator should be used in inline geometry at room temperature and allows one to perform experiments with a variety of sample environments. In addition, its performance should be demonstrated on application to high pressure experiments. The description and design of the new high energy resolution monochromator for the 121 Sb resonance are presented in chapter 3. The detecting system and experimental environment are presented in chapter 4.