Drift in lower extremity joint angles measured with inertial measurement units during treadmill walking

KDP (Potassium dihydrogen phosphate) crystal is one of the artificially grown crystals that has attracted the most attention. Now the fast growth method, which may easily introduce the metal impurities, is widely investigated. These metal impurity ions seriously affect growth rate and optical properties of the crystal. In this paper, the metal impurities Fe3+, Ba2+ and Cu2+ were doped into the growth solution of KDP crystals. The content and distribution of these metal impurities in KDP crystals were analyzed by a 3 MeV proton beam. The results indicate the chemical composition of elements O, K and P did not change by the impact from the ion beam. The limit of detection of Fe3+ was calculated. The results show that the trivalent metal ions in KDP crystals are easier to enter the crystals versus divalent ions and most of them distributed uniformly in the crystal.