Compact retarding field energy analyzer for the tokamak ISTTOK boundary plasma

The retarding field energy analyzer (RFEA) remains the more reliable diagnostic to measure the ion temperature in the boundary plasmas of magnetic fusion devices. A compact, simple design and inexpensive RFEA has been developed for investigations on the tokamak ISTTOK. It consists of a stainless steel pinhole (with a diameter of 0.6mm), three fine nickel grids with a separation of 1mm, and a collector, all insulated by mica. All the components are placed inside a boron nitride housing with dimensions of 14×14×23mm3. The RFEA has been tested in both ion and electron modes. The conditions of the RFEA operation are discussed, and preliminary measurements of the ion and electron temperature profiles presented.