Reduction of plasma density in the Helicity Injected Torus with Steady Inductance experiment by using a helicon pre-ionization source

Aaron C Hossack; Taylor Firman; Thomas R Jarboe; James R Prager; Brian S Victor; Jonathan S Wrobel; Timothy Ziemba

doi:10.1063/1.4824707

Reduction of plasma density in the Helicity Injected Torus with Steady Inductance experiment by using a helicon pre-ionization source

Rev Sci Instrum. 2013 Oct;84(10):103506. doi: 10.1063/1.4824707.

Authors

Aaron C Hossack¹, Taylor Firman, Thomas R Jarboe, James R Prager, Brian S Victor, Jonathan S Wrobel, Timothy Ziemba

Affiliation

¹ Department of Aeronautics and Astronautics, University of Washington, Seattle, Washington 98195, USA.

PMID: 24182109
DOI: 10.1063/1.4824707

Abstract

A helicon based pre-ionization source has been developed and installed on the Helicity Injected Torus with Steady Inductance (HIT-SI) spheromak. The source initiates plasma breakdown by injecting impurity-free, unmagnetized plasma into the HIT-SI confinement volume. Typical helium spheromaks have electron density reduced from (2-3) × 10(19) m(-3) to 1 × 10(19) m(-3). Deuterium spheromak formation is possible with density as low as 2 × 10(18) m(-3). The source also enables HIT-SI to be operated with only one helicity injector at injector frequencies above 14.5 kHz. A theory explaining the physical mechanism driving the reduction of breakdown density is presented.