The effect of tube geometry on the chiral plasma

Abstract

A chiral plasma plume has recently been reported inside a circular quartz tube without the use of an external magnetic field. It is believed that the quartz tube plays an important role in the formation of the chiral plasma plume. In this paper, to better understand how this interesting structure is generated, the effect of the tube geometry on the chiral plasma is investigated. First, the effect of the thickness of the tube wall on the chiral plasma is investigated. It is interesting to find that a too thin or too thick tube wall is not favorable for generating the chiral plasma. The chiral plasma plume can be obtained only at the tube wall thickness of 2 mm. Second, the effect of the diameter of the tube on the chiral plasma is investigated. It is found that, when a tube with an inner diameter of 2 mm is connected with a tube with an inner diameter of 4 mm and the high voltage electrode is placed in the tube with an inner diameter of 2 mm, a diffuse plasma is generated in the tube with an inner diameter of 2 mm, it propagates into the tube with an inner diameter of 4 mm, and a chiral plasma can be obtained at a distance of about 2 cm away from the joint of the two tubes. Third, to further understand how the tube diameter affects the appearance of the chiral plasma, horn shaped tubes with different opening angles are tested. It is found that, when the opening angle is 5°, the chiral plasma formation in the straight part of the tube can maintain the chiral shape and keep propagating in the horn shaped tube but with a much longer pitch. Fourth, to disrupt the axial symmetry, square quartz tubes are used. No chiral plasma can be obtained in the square quartz tubes under all experimental conditions. In addition, when a circular quartz tube is connected with a square tube, the chiral plasma formation in the circular quartz tube changes to a straight plasma plume in the square tube. Finally, the high voltage electrode is placed away from the center of the circular tube to disrupt its symmetry, and it is found that the chiral plasma plume can always be seen even if the high voltage is placed next to the inner wall of the tube.