Characteristics Of Arc-cylinder Focusing Self-magnetically Insulated Ion Diode High-intensity Pulsed Gas Ion Beams

Magnetically insulated ion diodes are the core components of high-intensity pulsed ion beam（HIPIB）equipment.In order to expand the application of high-intensity pulsed ion beam technology in the field of surface engineering,it is urgent to develop high-current pulsed ions with long life,stable parameters and low maintenance costs.In this paper,based on the TEMP-6 HIPIB equipment,combined with the transformation and upgrade of the bipolar pulse power supply system,an arc cylinder focused self-magnetic insulating gas ion diode was designed,and the bipolar pulse discharge characteristics of the high-intensity pulse gas ion source were studied.Diagnosis of total energy and focal energy density of HIPIB based on infrared thermography,measurement of ion beam current density using Faraday cup,analysis of ion composition based on ion beam time-of-flight method,and research on ion beam energy density,ion beam current density and ion composition.Discusses the main influencing factors of ion beam output stability,and proposes a method to improve the stability of ion beam.The effect of the negative pulse amplitude and delay time of the ion diode bipolar pulse voltage on the HIPIB parameters at a vacuum background pressure of 5 mPa was experimentally studied.On this basis,the effect of different gases（N₂,CH₄,CO₂,H₂）on the diode anode on the output parameters of HIPIB was studied.The results show that under the background pressure,the negative pulse amplitude increases from 230 kV to 320 kV,single N⁺,mixed N⁺and N²⁺,and single N²⁺ion beams are obtained,respectively.When the delay time increased from 400 ns to 600 ns,the total energy of HIPIB and the focal energy density first increase and then decrease.Considering the amplitude and stability of the ion beam energy density,the pulse time 450 ns and ion diode cathode and anode are determined.The appropriate conditions with a gap of 9¹1 mm are used to carry out subsequent experimental research on the introduction of gas.Fixing the same amplitude negative pulse 320 kV and delay time 450 ns,the different energy introduced into the anode led to different total energy and focal energy density of HIPIB output.When CH₄ is introduced into the anode,the total energy and focal energy density of HIPIB are the largest.The main components of the ion beam are C²⁺and H⁺.When CO₂ is introduced into the anode,the main components of the ion beam are C²⁺and C³⁺.When H₂ is introduced into the anode,the main component of the ion beam is N+,and a small amount of H⁺.The experiment studies the stability of multiple pulse discharges.And using the energy fluctuation rate as the stability evaluation index parameter,the energy density change rate Kq with the number of times is obtained by linear fitting for quantitative evaluation of HIPIB stability.The influence of vacuum background pressure,different anode surface materials,and improved cathode structure on the output stability of HIPIB was analyzed.The results show that at a background pressure of about 5 mPa,the stability of HIPIB is significantly reduced as the continuous output is increased to 25 pulses,the average total energy is 34 J,and the fluctuation rate is 18%;the average focus energy density is 2.9 J/cm²,the fluctuation rate is25%,and Kq is-75.1%.Nitrogen is introduced into the anode to significantly improve the stability of the HIPIB multi-pulse output.When the working pressure of nitrogen reaches 10mPa,the average value of the total energy of 25 shots pulses HIPIB is 37 J,with a fluctuation rate of 11%;the average value of the focal energy density was 3.4 J/cm²,with a fluctuation of26%,Kq is+17.3%,which significantly improves the stability of HIPIB multi-pulse output.As the background pressure increases from 5 mPa to 100 mPa,the HIPIB focal energy density,ion beam current density,and total energy all show a decreasing trend,and the fluctuation of the focal position gradually increases.At the same time,different anode surface materials also have a significant effect on the total energy and focal energy density of HIPIB.When the back pressure is 5 mPa,using copper anode and titanium anode,the Kq of 25 consecutive pulses of HIPIB is-26.7%and-82.9%respectively.The nitrogen pulse can still significantly improve the HIPIB multi-pulse stability of different anode materials.The Kq values of HIPIB for 25shots pulses were+5.9%and+2.1%,respectively.