Transverse injection of plasma into a linear, stellarator-like magnetic field

The plasma injector described is capable of injecting approximately 8*1016 ion-electron pairs into the separatrix of a linear, stellarator-like magnetic field (i.e. an axial magnetic field, plus the magnetic field f rom an l=3 helical winding). A further approximately 4*1017 ion-electron pairs go to the vacuum walls and are lost, during the injection. The total energy of the injected plasma trapped in the separatrix is approximately 5J, and the transverse ion temperature is in the range 100-300 eV, depending upon the magnitude of Bz. The plasma enters the magnetic field by polarization and E*B drift, in agreement with the results of workers studying other types of transverse injector. The speed at which the plasma enters the magnetic field is low ( approximately 3*104 m/sec). A theory is described, which attempts to explain some of the plasma loss taking place during the injection. A double Langmuir probe study of the injected plasma shows that the electron temperature has an upper limit of approximately 20 eV. Measurements with an ion energy analyser show that the ions are moving with mean energy approximately 50 eV along the magnetic field. Finally, a prediction is made of the suitability of this sort of injector for filling a large toroidal stellarator.