Vacuum duty cycle

A static fill, an effusive beam or a supersonic nozzle can be used for the introduction of the gas sample,. The supersonic nozzle has the advantage of refrigeration, and one may study rotationally and vibrationally cold molecules, or even stabilize otherwise inaccessible van der waals molecules. Finally, when operated in a pulsed mode, the nozzle cycle can be matched to the duty cycle of the laser to optimize the measuring conditions and improve the background vacuum. 

We will see later that the characteristics of vacuum triodes are replicated in npn junction transistors, albeit by a very different mechanism. One can operate very well with vacuum tubes, but they are more costly and difficult to manufacture and are prone to relatively early failure, mainly due to the tube becoming "gassy" with the evaporation of W from the filament or from vacuum breakdown, due to the prolonged heating of the vacuum tube. The typical vacuum tube duty cycles (a few thousand hours) are much inferior to the duty cycles of transistors. 

A TOF mass analyser requires a pulsed ion introduction. In an electrospray-TOF combination, the duty cycle is an important issue. A significant improvement in the duty cycle can be achieved in an ion-trap-TOF hybrid instmment the ions from a continuous ion source are accumulated in the ion trap between two ion introduction events. An ion-trap-TOF hybrid instrument was first described by the group of Lubman [68-69]. The system consists of an atmospheric-pressure ion source with a vacuum interface, a set of Einzel lenses, an ion-trap device, and a reflectron time-of-flight mass analyser. The system was applied for fast analysis in combination with a variety of separation techniques [70]. 

Operate continuously during their useful life, although the pressme-reduction portion of a vacuum vapor degreasing cycle is periodic. Many vacuum pumps are designed for continuous duty. 

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