An ion beam structure includes a gas container, such as a cylindrical can having first and second apertures through the center of the top and bottom walls respectively of the container such that a narrow ion beam is passed through the apertures and the center axis of the can and onto a target specimen such as a mask or chip or other article of manufacture disposed closely below the bottom of the can. The can may further include deflection means for applying voltages and/or magnetic fields to locations on the can (i.e., top, bottom, sides) to direct secondary charged particles such as electrons emitted from the specimen onto an electron detection means such that the structure functions as an imaging system. The electric and/or magnetic fields may be employed to increase the collection efficiency of the detector and thereby improve the quality of the image by increasing the signal to noise ratio. When the collected image produced by the secondary charged particles indicates that a repair or other modification be performed, a gas is introduced into the can from a gas reservoir via a tube. The gas, which contains first type particles (i.e. gold atom, tungsten atom, etc.) leaves the can via the bottom aperture and is adsorbed onto the nearby target specimen surface. The ion beam, containing second type particles (i.e. gallium ions) passes through the gas with minimum interaction and strikes the target specimen surface to decompose the adsorbed gas and the decomposed first type particles to provide the modification such as repair to the specimen (mask or chip) surface.