Ion Gauges (IG) are hot cathode gauges. They comprise a filament that acts as an electron source, a grid that accelerates the electrons and a collector to detect ionized gases formed by collisions between the electrons and atoms inside the grid. Tungsten (W) can be operated up to 100 Watts being a good ion gauge filament. However, In and Ga modify the work function of the W filaments, and so either Yttrium (Y) or Thorium (Th) coated Iridium (Ir) filaments are more better choices for III-V systems. This is especially true for ion beam flux monitors (BFMs, aka monitoring ion gauges (MIGs)). The Ir-filament can be operated with a controller, which improves stability. The QNC-MBE tool is equipped with IGs in all its chambers and a BFM for flux monitoring.