\section{Background}
The instrument design of \acs{AHEPaM} has undergone optimisations driven by \acs{GEANT4} particle simulations as well as the thermal and structural analysis \cite{ahepam-djf}. Based on those results, it has been decided that the implementation of a Cherenkov detector is beneficial and the sizes of the different detectors have been optimized in order to achieve the different measurement requirements \cite{ahepam-sr}. The overall design, however, remains remarkable similar to the one proposed in \cite{Technical_Proposal} except for the fact that we have shown that a surrounding anti-coincidence plastic scintillator can be omitted with a sophisticated design of the SSD geometry. \newline
Despite being significant, the delays in schedule caused by these detailed studies are out-weighted by the benefits of having an instrument of which we are certain that it can full-fill the requirements and the reduced risks of necessary design changes in later phases of the project and for a possible FM. \newline
Based on this design philosophy we have also decided to build a DM very similar to the FM rather than a heavily descoped model. As stated in the \cite{ahepam-ddf}, the DM features the same BGOs and Cherenkov as the FM design. The majority of the electronics (\ac{PMT}, preamps, shaper, etc.) will also be similar to the FM.