Prototype sector magnets for the GeV Electron Microtron (GEM)

Three prototypes of the sector magnets for GeV Electon Microtron accelerators were designed. One was built and two are under construction. The first is a full scale, 168 ton prototype for one half of a 2 GeV Double Sided Microtron (DSM) sector magnet. It is demonstrated that the required close tolerances for flatness and parallelism can be met. The second magnet is an approximate two thirds scale model of one step at the low energy end of the hexatron sector magnet designed for the 4 GeV Electron Microtron (GEM). The measured fields demonstrate that the field falls off faster than an Enge short tail and error fields are at low levels and are controllable. A third prototype magnet exactly duplicates the full scale geometry of the first three full orbits of the GEM sector magnet from entrance to exit points. It will permit high precision measurements and corrections of field errors and verify the 3-D computer program, TOSCA.