Dynamic Behavior of Plasma in a Cascade Plasma Torch with External Magnetic Field

Hiroki Saito, Hikaru Matsumoto, Takayasu Fujino

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


The effect of operating conditions on the arc voltage fluctuations and dynamic behavior of plasma were investigated for a cascade plasma torch with an external magnetic field. The key factors that affect the fluctuations of the arc voltage were studied, which is useful for generating stable plasma jets. A ring-shaped permanent magnet was used to produce an external magnetic field having a flux density of approximately 0.27 T at the center of the magnet. The operating current, gas flow rate, and anode–cathode distance were varied in the range of 40-160 A, 10-40 L/min, and 0-10 mm, respectively. The width of the ring-shaped anode was set to 1 mm or 3 mm. The end-on images of the plasma were captured by high-speed photography, and the associated arc voltage was measured simultaneously. When an anode of 1 mm width was used, a periodic sine-like voltage waveform with low amplitude was observed at a low gas flow rate. In that condition, an arc root rotated along the anode wall continuously with no observable breakdown process. The rotational frequencies of the arc exceeded 1 kHz and were strongly dependent on the square root of the operating current.

Original languageEnglish
Pages (from-to)333-343
Number of pages11
JournalJournal of Thermal Spray Technology
Issue number3
Publication statusPublished - 2020 Feb 1
Externally publishedYes


  • arc fluctuations
  • cascade plasma torch
  • external magnetic field
  • high-speed photography
  • voltage measurement

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Materials Chemistry


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