LI-ERDA uses low voltage single-ended accelerators, whereas the HI-ERDA uses large tandem accelerators. These techniques were mainly developed after heavy ion accelerators were introduced in the materials research. LI-ERDA is also often performed using a relatively low energy (2 MeV) 4He beam specifically to depth profile hydrogen. In this technique, multiple detectors are used: at backscattering angles to detect heavier elements by RBS and forward (recoil) detector to simultaneously detect the recoiled hydrogen. The recoil detector for LI-ERDA typically has a “range foil” which is typically a Mylar foil placed in front of the detector for blocking scattered incident ions but allow lighter recoiling target atoms to pass through to the detector. Usually a 10 µm thick Mylar foil is able to completely stop 2.6 MeV He+ ions but allows the recoiled protons to go through with a low energy loss.