A flow distributor for mounting in an inlet of a heat exchanger includes a nose cone and one or more diverting rings. The invention provides a signal lamp that includes a housing having an opening and including a substrate located opposite the opening, a lens disposed within the opening, and a plurality of clusters with each of the clusters comprising a plurality of light emitting devices. The mass selective sampling is suggested for improving duty cycle of o-TOF MS, for injecting ions into a multi-reflecting TOF MS in a zoom mode, for parallel MS-MS analysis in a trap-TOF MS, as well as for moderate mass filtering in fragmentation cells and ion reactors.