VICI’s newest member of the Pulsed Discharge Detector (PDD) family, the miniPDD helium ionization detector, is also the smallest and thriftiest.
The miniPDD uses around one fifth (20 percent) of the amount of helium as the VICI Valco D-3 and D-4 versions, giving up only a bit of sensitivity and dynamic range in return.
The device is approximately one half the size of the D-4, but has nearly the same sensitivity — around 100 ppb for fixed gases. With its reduced size, weight, and helium consumption, it is particularly well suited to portable applications, or to any situation in which the high cost of helium becomes a consideration. One might therefore suggest that the miniPDD is an appropriate product release for the currently tight times of helium supply and availability.
It can be paired with other Valco components (controller, pulse module, helium purifiers) or can be purchased alone for use with existing components.
VICI PDDs (pulsed discharge detectors) utilize a stable, low powered, pulsed DC discharge in helium as an ionization source. Eluants from the column, flowing counter to the flow of helium from the discharge zone, are ionized by photons from the helium discharge. The bias electrode(s) focus the resulting electrons toward the collector electrode, where they cause changes in the standing current, which are quantified as the detector output. Performance is equal to or better than detectors with conventional radioactive sources.
In the helium photoionization mode, the PDD is a universal, non-destructive, high sensitivity detector. The response to both inorganic and organic compounds is linear over a wide range.