500 kV accelerator
The 500 kV accelerator is an open, single ended machine, which means it has no tank around the high voltage terminal and its ion sources are on the high voltage terminal. Thus his operation is much simpler compared to a tandem. Another advantage is …
… that the ion sources operate with positive ions and no charge exchange is necessary. As a consequence, the beam intensities are usually much higher and can reach up to several 100 µA.
The 500 kV accelerator can be operated with three ion sources namely a Duoplasmatron source, a Penning source and a hollow cathode ion source. This allows to accelerate a large variety of ions. In particular, the acceleration of noble gas ions is possible also. The ions are extracted from the ion source by a potential of up to 30 keV and analyzed by a 90° magnet located still on the high voltage platform. Therefore, only the desired ion species is accelerated by the high voltage potential.
The high voltage is generated by a cascade consisting of two Cockroft-Walton type columns, which are designed to achieve a high stability (better that 3 V) and small ripple of the high voltage. The ripple can be trimmed to less than 10 V.
After the acceleration the ion beam can be focused by an electrostatic quadrupole triplet and guided by a switching magnet to different set-ups for ion implantation or nuclear reaction analysis. The entire facility is aligned to a beam line of the tandem-accelerator so that a connection can be established and a beam from the tandem can be guided to the measuring and implantation stations also.
The accelerator is used recently mainly for he implantation of noble gas ions and for material analysis using low energy, proton-induces resonances (NRRA).