Method for stabilizing the updated model in iterative seismic data inversion so that the model-simulated data for the next iteration does not \u201cblow up. The housing provides complete shielding of personnel from X-rays except towards the inlet and is movable relative to the processing unit to a first position for analysis at which the unit outlet is collocated with the inlet and at which the processing unit completes the shielding of personnel from X-rays towards the inlet. The assembly includes at least one formation evaluation instrument for determining a characteristic of formation fluid, and a pump which draws the fluid into the assembly. Smaller secondary tables are also provided that set up separately from the primary table.