Complex sentence: The coated pellet was surrounded by a beryllium shell with 2 cm outer diameter and 0.6 cm thick walls, with 15 concentric, wedge-shaped, 2.09 mm deep latitudal grooves in its inner surface that was also coated with gold and nickel.
Split into simpler sentences: The coated pellet was surrounded by a beryllium shell of 2 cm outer diameter with walls 0.6 cm thick. The inner surface bore 15 concentric, wedge-shaped latitudal grooves and was, like the inner sphere, coated with gold and nickel.