The MPRu is an upgrade of the magnetic proton recoil (MPR) neutron spectrometer that has been used for 14 MeV DT neutron measurements at JET during the DTE1 (1997) and TTE (2003) campaigns. In this contribution the principles of the MPR and its upgrade will be presented. The MPRu allows measurements of the full range of fusion relevant neutron energies, 1.5–18 MeV, including the 14 MeV DT neutrons, now with significantly reduced background, and also new high-quality measurements of the 2.5 MeV DD neutron component. This improvement is made possible by the use of a new proton recoil detector in combination with custom-built transient recorder cards. The importance of these nstrumental improvements for extending the use of the MPRu in diagnosis of D and DT plasmas will be discussed. Results from the first 2.5 MeV
measurements performed with the MPRu during JET high level commissioning in April 2006 are presented.