The Mechanism Research Of Corona Gun Discharge Character

Corona discharge is one of the seldom methods to produce low temperature plasma by directly discharging, under atmosphere pressure. Because of its characters as simple structure, high efficiency and low power cost. it is widely used in the industry fields. This thesis will discuss an discharge set named corona gun. which is used in the non-contact semiconductor C-V testing device.Actually, corona gun is a charge emission set, by which charged particles are ionized and focused to be send out from a pin hole. In order to get the most stable and efficient discharge status, a series of researches were done, including basic mechanism, experimental phenomena and numerical modeling result.Firstly, the different breakdown process between positive corona and negative corona is described. Positive corona is begin with discontinuous stream mechanism. But negative corona mainly depend on the electron avalanche. The self-sustained discharge mechanism is also different between positive and negative corona. The former gain the seed electron by photoionization, but the latter is by the second electron emission. As a result, different experiment phenomena can be seen.Secondly, gases such as Argon, Nitrogen, Oxygen and compressed dry air(CDA) are used to discharge in the experiment, and some interesting current curve is obtained. When Argon is used, its current curve is very unstable, and strong stream effect can be found in the positive corona discharge. Although, Nitrogen brings the stable positive current curve, it has a great electron avalanche effect in the negative corona discharge. Oxygen is the most stable discharge gas both at positive and negative current, but its awful oxidation species like ozone created during the discharge will make unexpected compound deposition in the reactor, which cause a big problem for the corona gun to be used for a long time. Luckily. CDA is found to be the ideal discharge gas. because the mixture of Nitrogen and Oxygen makes them improved their weakness. The corona gun discharges at a stable condition under the CDA. and the little exhaust gas can be easily flow out by a controlled flux rate. So CDA is considered as the best work gas. and the experiment data of the other gas also provide a good reference to deal with the more mechanism.Lastly. a numerical modeling way is built up to simulate the electrical field and the charge drifting behavior. By the numerical solution of possion equation, the field can be calculated, and then the movement of charged particle will be simulated by the dynamics rules. On the result image, you can find the high electrical field near the tip needle and the drifting track of the charge from ionization, and the effective factors will be know. This work not only supply the wonderful information for the theory development. but also set up a helpful design method for the corona gun improvement.In a word. the work of corona gun discharge character mechanism research get the ne(?)ul experiment analyse and simulation results. It is possible to use this theory mechanism and design program to find the best discharge status and particle emission behavior for the likely system.