Development of a high current movin Arc gas discharge switch for the FAIR magnetic horn

The planed Facility for Antiproton and Ion Research (FAIR) is a new international accelerator laboratory at the GSI in Darmstadt, Germany. One research topic at this facility is aimed to protons and anti protons colliding experiments. After generation of these antiprotons strong magnetic fields are necessary to focus the antiprotons. To achieve this high magnetic fields a magnetic horn will be used. To generate for this application the necessary high magnetic field the designed stripline of the pulse forming network (PFN) has to handle a peak current of 400kA with a pulse length of 20μs. Currently the only possibility to handle this high current is the use of mercury filled Ignitrons. The plasma physics working group at the University of Frankfurt develops a mercury free switch, which is able to replace the Ignitrons in the PFN of the magnetic horn. This contribution shall give an overview about the development of a gas discharge switch with minimized local electrode erosion. The experimental setup of the switch consists of coaxial electrodes, similar to the geometry used for plasma focus devices. The main discharge between the coaxial electrode system will be initiated by a trigger predischarge. After the ignition of the main discharge between the coaxial electrode system and due to the interaction of the induced radial magnetic field with the plasma, the gas discharge will be accelerated to the open end of the coaxial electrode system¹. This acceleration of the plasma sheet is due to the Lorentz force, which interacts with the discharge. Therefore the switch will be called a Lorentz Drift Switch (LDS). For the special application of the magnetic horn to provide enough charged particles several of these coaxial devices will be stacked together in a parallel.