A third type of detector is the gas ionization detector. The gas ionization detectors have some advantages over silicon detectors, for example, they are completely impervious to beam damage, since the gas can be replenished continuously. Nuclear experiments with large area ionization chambers increase the particle and position resolution have been used for many years and can easily be assimilated to any specific geometry. The limiting factor on energy resolution using this type of detector is the entrance window, which needs to be strong enough to withstand the atmospheric pressure of the gas, 20-90 mbar. Ultra-thin silicon nitride windows have been introduced, together with dramatic simplifications in the design, which have been demonstrated to be nearly as good as more complex designs for low energy ERD. These detectors have also been implemented in heavy ion Rutherford Backscattering Spectrometry. Figure 7 shows the Gas Ionization chamber with Isobutane as the detector gas.