This MKS Granville Phillips Iridium glass ion gauge tube is a test gauge vacuum simulator, pumped down and pinched off at 1 X 10^-5 or lower. The MKS Granville Phillips thoria coated iridium (IR) filament configuration can be used in any clean application, but is particularly practical in potentially oxygen rich environments. All IR filaments have a thoria coating, which increases electron emission to approximately the same level as tungsten filaments. Iridium filaments, however, can be strongly degraded by metallic or organic contaminants, resulting in poor accuracy (filaments are easily poisoned by oil back-streaming from diffusion or mechanical vacuum pumps). Thoria coated IR is very resistant to oxidation, and can even tolerate brief exposure to atmosphere during operation and will not damage or shorten the filament life.

Iridium ion gauge tubes can be typically identified by the single white "hair-pin" shaped filaments and have four external leads at the plug end. This MKS Granville Phillips gauge tube works with most hot cathode ion gauge controllers made by MKS Granville Phillips, MKS Instruments, Perkin Elmer, Varian, & Veeco.