An Arrowhead-Type Microwave Low-Temperature Plasma Jet at Atmospheric Pressure

Plasma consists of a collection of ions, electrons, and bound neutral particles, and the whole is a neutral state of matter. Plasma can be divided into two types: high-temperature plasma and low-temperature plasma. Low-temperature plasma is plasma that occurs at room temperature, although the temperature of the electrons is very high. Low-temperature plasma can be used for welding, sterilization, melting, and other applications. In this article, an arrow-shaped microwave low-temperature plasma jet based on a coaxial structure is proposed. The device has the advantages of small volume, low power consumption, high stability, and self-excitation. The plasma length can be varied by changing the velocity of the plasma jet or the microwave power. The argon discharge can be excited at atmospheric pressure with a microwave power of 3.2 W, and its minimum maintenance power is 1.57 W. The optical emission spectra of the plasma show that it contains highly active OH radicals and a large number of energetic particles. Under proper operating conditions, the flame tail treatment of human fingers only heats up to $36.7~^{\circ }$ C for 30 s. This portable device can be efficiently used in medical cosmetology and material surface treatment.