The 4 MV tandem accelerator system provides a high energetic ion beams of many different species in a wide range of intensities and energies. These ion beams are used for material modification, material analysis and further applications. Examples are the implantation of semiconductors, productions of vacancies or defect, thin film compositional analysis or the depth profiling of hydrogen bearing materials.
Mode of operation:
The facility consists of three different ion sources, the tandem accelerator itself and a variety of magnets for filtering and guiding the ion beam to the desired position. In a first stage negative ions are generated in one of the ion sources. Using a pre-acceleration voltage, the ions, charged atoms or molecules, are transported to the accelerator through a bending magnet. In the first half of the accelerator the ions are attracted to the central part by a positive potential of up to 4 MV of the terminal. In this terminal, the ions pass a gas filled channel. The stripping of electrons due to interactions with the gas leads to the formation of positive ions. In case of accelerated molecules, the loss of electrons additionally provides the breaks-up into positively charged atoms. From this moment, the positively charged ions are repelled by the positive terminal and are accelerated further in the second half of the accelerator. Thus, the acceleration potential is used twice, which is the reason for name "Tandem" accelerator. To provide a pure, monoenergetic beam, after the accelerator the ions are filtered by an analyzing magnet. Finally, a further magnet bends the beam into the particular line of a specific setup. Focussing and beam diagnostic elements are used to control the beam transport through the whole system.