This BA tube is constructed without an envelope; it is designed for mounting in a vacuum system port with a flange which mates with the ConFlat® flange or with an NW 40 KF flange on which the tube structure is built. The tube is available with two types of grid structure, a simple double spiral as shown in the attached figure (standard structure) or a completely enclosed cage constructed of fine, welded tungsten wire (ultra high vacuum structure). The standard grid structure can be outgassed by resistance heating; the ultra high vacuum (UHV) structure must be outgassed by electron beam. When constructed on a ConFlat flange the tube is bakeable. The UHV tube includes a shield around the collector feedthrough and a very fine collector wire; both these features permit measurement of lower pressure than the standard structure permits.
The standard configuration tube is available with either a single, replaceable thoria-coated iridium filament or a single, replaceable tungsten filament. The UHV tube is available with either double, replaceable thoria-coated iridium filaments or double, replaceable tungsten filaments. The tube’s gauge factor depends on its mounting configuration; when mounted in a 1.5” diameter pipe the nominal gauge factor for the standard configuration is 6/Torr; the gauge factor for the UHV tube is 20/Torr.
The structure is fragile; the tube must be handled with care, particularly in the UHV configuration When mounted in a close fitting pipe, the filament will heat the pipe producing localized outgassing and thus high pressure readings until the area around the filament cleans up. The nude tube is often used to prevent inadvertent air release of a vacuum system through breakage of an externally mounted glass tube. Replacement filament and grid assemblies are available.
In the drawing (standard configuration) the ion collector wire is connected to the pin labeled C, the ends of the grid are connected to the pins labeled F, and the filaments are connected to the pins labeled F.
BA-4/C Nude Ion Tube, UHV configuration, uncalibrated, constructed on a 2-3/4 Conflat® flange, specify tungsten or thoria coated iridium dual filaments by adding /2W or /2Ir: $390.00.
BA-4/KF40 Nude Ion Tube, UHV configuration, uncalibrated, constructed on an NW 40 flange, specify tungsten or thoria coated iridium dual filaments by adding /2W or /2Ir: $390.00.
BA-4/C Nude Ion Tube, standard configuration, uncalibrated, constructed on a 2-3/4 Conflat® flange, specify tungsten or thoria coated iridium filament by adding /W or /Ir: $350.00.
BA-4/KF40 Nude Ion Tube, standard configuration, uncalibrated, constructed on an NW 40 flange, specify tungsten or thoria coated iridium filaments by adding /W or /Ir: $350.00.
RFA-1 Replacement filament assembly for UHV configuration: $59.00. Specify tungsten or thoria coated iridium.
RGA-1 Replacement grid assembly for UHV configuration: $110.00.
For calibration to NIST traceable gauge factor add /CERT: add $150 for each filament calibrated.
To order call 617-524-0465.