LCIF Measurements of a Magnetically Confined Microwave Plasma Source

Split-ring resonators (SRR) are a type of microstrip resonator. When designed correctly, SRRs can be used as a low power plasma source. Previous work tried to use a SRR device as a plasma source at low pressures; however, the resulting electron densities were relatively low for the desired application. This was due mainly to the electrons diffusing too quickly. This work seeks to enhance the plasma produced by a SRR through the addition of magnetic cusp fields produced by permanent magnets. These cusp fields should confine the electrons and reduce electron diffusion. To determine the effect of the magnetic field, a parametric study is done. This is done by varying the magnetic field, forward, power, and pressure in a SRR helium plasma3. In this work, four magnetic field cases, including a no magnetic field case, are used. Forward power is supplied at 10, 11, and 12 W and operating pressure is set to 250 mTorr, 500 mTorr, and 1 Torr. To compare the plasma properties of each case, electron temperature and electron density measurements are acquired using laser collisional induced fluorescence. Results seem to indicate that the electrons were confined by the magnetic field lines; however, contrary to expectations the electron density decreased with the addition of the magnetic field lines.