The so called High Flux Test Module (HFTM) represents the component of IFMIF (International Fusion Irradiation Facility) in which material specimens are being placed that accumulate high neutron induced damage rates (≥20 dpa/fpy). Damage rates of this magnitude are limited to a volume of ∼500 cm3 (attenuation in beam direction) behind a beam footprint of 20 × 5 cm2, so the high flux region of the module is contained in a flat faced, cuboid volume of 5.6 cm depth. Efforts for a high spatial utilisation and the demand for a high neutron transmission lead to a thin-walled container design. As an efficient, space-saving method to cool the container and the material specimens, an array of mini-channels (1 mm gaps) through which low pressure (0.3 MPa) helium gas is flowing is established. Installed closely to the target and due to space constraints by other irradiation modules, the HFTM is implemented as a slender and tall construction with features that are challenging for pressure equipment. Experimental studies on a 1:1 prototype of the HFTM-DC (double compartment) have been made in the Helium Loop Karlsruhe – Low Pressure (HELOKA-LP) during 2015. The experiments also included intensive testing to demonstrate the mechanical reliability of the HFTM under IFMIF relevant operation conditions. Therefore, the module was instrumented with numerous sensors which measure displacement, deformation and mechanical strain. The reactions on temperature and pressure loads were studied. In this paper the experimental results will be presented and compared to the numerical (FEM) simulation studies.