Ions that are transported from an ion source to a mass spectrometer for mass analysis are often accompanied by background particles such as photons, neutral species, and cluster or aerosol ions which originate in the ion source. The dust collector is disposed on a rearward side of the vacuum cleaner main body and wherein the exhaust outlet is disposed on a front surface side of the dust collector. Further, maintenance comprises performing a cleaning phase that streams water from a nozzle located remotely from the barrier such that water is sprayed into the bowl with sufficient force to cause water to swirl around the barrier, which cleans the bowl and discharges debris and contaminated water in the bowl when such debris and contaminated water crosses in line with the water stream. The housing is ultra-thin to enable penetration of the electron beam therethrough even though a liquid specimen is injected into the housing. The elongated tube member is then cut to predetermined sizes, the resulting roller tube being joined to the roller handle assembly. The plurality of lockers are combined with the front mask and include guides that are inserted into the second slots and stoppers that extend from the guides.