The qualification of plasma facing materials for the ITER divertor is a key issue in present fusion research. Erosion and redeposition of graphite and tritium accumulation in subsequently formed carbon layers on the target plates and in remote areas is one of the most critical questions associated with the life time of Carbon Fibre Composites (CFCs) on the lower target plates of ITER. To study these effects in a time and space resolved mode a set of six Quartz Microbalance (QMB) systems was installed in the JET divertor in the shutdown 2004 at various poloidal locations. They measure in situ (shot resolved) the mass changes of eroded or deposited layers /1/ on top of a quartz crystal. This contribution reports in particular on the measurements from a QMB which was placed in the Private Flux Region (PFR) below the supporting wedge of the Load Bearing Septum Replacement Plate (LBSRP) of the MKII-HD divertor with a direct view to the vertical tiles of the inner divertor, thus representing somewhat the geometrical situation in the inner divertor of ITER.