Study of the Effects of Guide Field on Reconnection in MRX

In magnetic reconnection, the presence of the third magnetic field component, or guide field, reduces reconnection rate and tends to form O-shaped diffusion regions~\footnote{M. Yamada et al., Phys. Rev. Lett. 78, 3117 (1997).}. In the Magnetic Reconnection Experiment (MRX), cohelicity merging of two plasma toroids created by a pair of flux cores can produce guide field, however, the magnitude is not easily independently controlled and the field is globally nonuniform. A new toroidal field coil set powered by a 50 kJ capacitor bank capable of producing a uniform guide field with strengths up to 1000 G has been installed on MRX. Other guide field hardware is also described. Initial results of reconnection rate, resistivity, and current sheet tilting and as a function of guide field strength are presented as available. Ion flows are measured with a new Mach probe array, which allows simultaneous measurement of two components of the ion velocity at several points in and near the diffusion region.