Inficon Transpector MPH Operating Manual page 144

Total Pressure Plate
Transition Flow
Transmission Factor
Viscous Flow
Zero Blast
9 - 7
The total pressure plate, or collector, is an electrode in the ion source on
which at least a part of the ion beam impinges. The current striking this
plate is a function of the total pressure in the ion source.
Transition flow is that motion of gas molecules wherein the collisional
mean free path is approximately the same as the critical dimension of a
flow constraining element such as an orifice of tube diameter.
The transmission factor is the ratio of ion current detected at the exit end
of the mass filter (set to transmit a given mass) to the current of ions of the
same mass entering the filter from the ion source. Typically, the
transmission factor for nitrogen ions at 28 AMU is set equal to 1. The
transmission factor at other masses is given relative to that for nitrogen.
Viscous flow is that motion of gas molecules wherein the collisional mean
free path is less than the critical dimension of a flow constraining element
such as an orifice of tube diameter. The gas flow characteristics are
dominated by collisions between gas molecules.
Zero blast is the ion current which is not mass filtered and is detected
when the mass spectrometer is scanning near mass zero.
Transpector MPH Operating Manual