Study On The Charge Of Positive Dielectric Particles In Dusty Plasma

Dusty plasma is a complex system composed of electrons,ions,neutral particles and dust particles.In the plasma environment,dust particles are charged by collision with plasma electrons and ions,so the measurement of the charge of dust particle is an important research content in dusty plasma.Most of the previous dusty plasma experiments have studied the electrification of small dust particles suspended near the plasma sheath.These small dust particles are usually negatively charged,with a charge range of about 10~1～10~6e.When the dust particles are large,the electric field force of the sheath cannot overcome the gravity,so the particles cannot be suspended and will fall on the electrode plate.Because the electron density at the inner plate of the sheath is much lower than the ion density,the particles may be positively charged,and research on this is very limited.Recently,we have found some new physical phenomena such as abnormal diffusion of large medium particles on plates.In order to reveal the physical mechanism behind these phenomena,it is necessary to explore the charged state of particles first.In order to solve the above problems,the charge of charged particles moving on the lower plate in dusty plasma is studied by experiment and simulation.The uniform plasma is produced by DC discharge experiment.Under appropriate control conditions,the dielectric particles show a variety of motion states on the lower plate.When studying the charged amount of particles,this paper adopts a new method,that is,using the central elastic collision motion of charged particles in plasma,by analyzing the collision trajectory of charged dielectric particles when they collide,the relative velocity and other parameters of particle motion can be obtained,and finally the charged amount Q of particles can be obtained.The trajectory of particles with central elastic collision is closely related to the potential distribution around each particle.In this paper,we mainly consider two potential distributions of shielded Coulomb potential(Yukawa potential)and Coulomb potential,and analyze and discuss the charged amount of particles under these two potential distributions.We also studied the particle charge under different particle sizes and discharge conditions.In order to further reveal the motion mechanism of the positive dielectric ball,we also carried out numerical simulation,obtained the plasma parameters by fluid simulation,and simulated the surface potential distribution of the dielectric ball.The charged amount of the positive dielectric ball on the electrode plate is calculated according to OML theory,which is basically consistent with the experimental results.The results provide a basis for further study of various complex motions of charged particles in dusty plasma.