Electric charging of powder bed by ion and/or electron irradiation using an atmospheric pressure plasma jet

大気圧プラズマジェットから生成される正イオンや電子を用いて，粉体層内の粒子を荷電する実験を行った．ここでは，1 SLM（標準状態1 L/min）のヘリウムガスの供給によって有効荷電範囲を0.01 m[2]に設定した．誘電性粉体層（PTFE）の上層の粒子は数sで平衡帯電に達したが，下層の粒子は徐々に帯電し，1 minで定常値に近づいた．電荷は粉体層内を2 mm程度の深さまで移動し，上層より下層の粒子の方が平衡帯電量は大きくなることがわかった．また，電気抵抗があまり高くない粒子（マンガンフェライト）を帯電させることは難しいが，粉体層の下に誘電板を置くと，粉体層の最下層の粒子を荷電できることもわかった．Experiments were carried out on the electric charging of particles in a powder bed with positive ions and/or electrons, which were generated by an atmospheric pressure plasma jet. Here, the effective electric charging area was set to be approximately 0.01 m[2] by supplying 1 SLM (standard liter per minute) of helium gas. The upper layer particles of a dielectric powder bed (PTFE) reached equilibrium charging after a few seconds, while the lower layer particles were gradually charged, and the particle charge approached the equilibrium value in 1 min. It was found that the charges migrated up to a depth of 2 mm in the powder bed, and the lower layer particles had larger equilibrium charges than the upper layer ones. In addition, it was found that charging is difficult for particles that do not have very high electrical resistivity (manganese ferrite). However, the lowest layer particles could be charged by placing a dielectric plate under the powder bed