Emission Spectra Of Corona Discharge With Submillimeter Gap

With the continuous development of micro devices,the gas discharge problem in micro gaps has gradually become a bottleneck problem that restricts the performance improvement of these devices.Micro discharge is a gas discharge form in which the discharge is limited to a limited spatial range,with electrode gaps or electrode sizes in the order of sub-millimeters or less.When the electrode spacing is sub-millimeter,the discharge is generally in a transitional state from long gap to micro gap,and the mechanism of discharge is not fully clear.At this distance,the optical signal generated by discharge can be collected and analyzed.Therefore,in order to better explore the physical process of corona discharge under sub-millimeter gap,this article studies corona discharge under submillimeter gap through a combination of experimental and simulation methods.First of all,the self-built pin-plate discharge system with sub-millimeter gap（200-500μm）is used for corona discharge in atmospheric environment.The images of discharge under different air pressures are collected through optical lens,and the corona discharge pulse waveform is collected through oscilloscope.It is found that the negative corona discharge is divided into the initial stage of the Trichel pulse,the middle stage of the Trichel pulse,and the sawtooth waveform period with the increase of the applied voltage.The halo radius varies from 9.12μm increases to19.56μm.Pulse amplitude from 172μA to 250μA with the air pressure decreases.This article debugs the spectrometer and collects corona discharge emission spectrum information through the spectrometer.The influence of different air pressures on the amplitude of negative corona Trichel pulses was analyzed,and it was found that a larger average free path of electrons at low pressure would enhance the corona discharge related signals.The effects of voltage values,needle-plate distances,needle electrode curvature,and voltage polarities on the relative light intensity of the emission spectrum were analyzed.The experimental results show that the emission spectra of submillimeter gap corona discharge at atmospheric pressure mainly focus on the range of 290nm-410nm,which belongs to the second positive generation of N₂（C³Π_u→B³Π_g）.Secondly,The species of active particle is explored by emitting spectral peak and diagnose the electron excitation temperature through light intensity ratio method.The vibration temperature of N₂（C³Π_u→B³Π_g）second positive generation system is calculated by Boltzmann slope method.The variation of electron excitation temperature and vibration temperature at different voltages,different distances,different tip radii and different polarities is also discussed.The discharge power of the pin-plate electrode was calculated by P=UI.Explored the effects of different discharge powers on spectral relative light intensity,electron excitation temperature,and vibration temperature,as well as the effects of different discharge electrode properties on discharge power.Finally,the finite element simulation software COMSOL was used to simulate the DC negative corona discharge with 200μm spacing.The simulation Trichel pulse waveform was compared with the waveform collected in the experiment to verify the validity of the simulation.In order to better explore the micro physical process of negative corona discharge under submillimeter gap,change the secondary electron emission region in the simulation,and explain the influence of the secondary electron emission region on the Trichel pulse waveform,particle density,and electric field intensity from a micro perspective.