The spherical theta pinch and its applications

The Spherical Theta Pinch, formerly also referred to as low-frequency inductively coupled plasma (LF ICP) was developed at the Institute for Applied Physics in Frankfurt around 2008. It consists of a massive spherical coil of up to 10 windings which is arranged around a glas sphere of several 1000ml of volume. A capacitor bank is discharged through the coil, igniting a plasma inside the gas in the discharge vessel. The peak currents reach several tens of kiloamperes, the capacitor voltages more than 10kV. Gas pressures lie in the region of 1-200Pa. Average electron densities of more than 5×10²² m^-3 have been measured. This paper is meant to act as a reference and to give an overview about the former, ongoing and upcoming spherical theta pinch experiments in Frankfurt. The different investigated applications as an ion source, a VUV-flash lamp and as a plasma stripper are examined regarding their special requirements followed by the approaches which were taken to live up to those needs. A short introduction into the switch development at the institute is given, to show the subsequent replacement of lifetime limited and, in the case of ignitrons, potentially hazardous gas discharge switches by long living thyristor stacks which also contributed to the advance of the spherical theta pinch devices built. Finally an outlook on parallel and future developments is presented.