NEC utilizes two distinct support structure designs — U-series and S-series — depending on the application, the configuration, and the type of ion source used. Both the U-series and the S-series can be built in tandem or single ended configurations.
The column structure for a U-series system is divided into 1 MV sections. These sections are supported by insulating ceramic support columns and have unparalleled strength and durability. The columns are then connected to bulkheads that support the acceleration tube. This design is used for large, horizontal, single ended systems because they support the weight of a larger terminal with a more advanced ion source. The U-series design is also used for large, vertical systems over 6 MV.
The S-series systems differ from the U-series in that the column is composed of parallel Lucite plates surrounded by equipotential rings. The acceleration tube is supported inside the Lucite plates. The plates are supported on both sides of the tandem by large bulkheads and by the terminal in the middle. The S-series is mostly used in horizontal, tandem accelerators 6 MV and below, and single ended accelerators with a lightweight ion source.