A simulation of ion beam extraction and beam formation process for 150 keV/2mA ion implantor using SIMION 8.1. has been done. This simulation is aimed to provide an overview of the influence of the geometry and the effect of the variation of the voltage of both extractor and the acceleration tube of the ion source of ion implantor on the trajectory, beam diameter and beam emittance. The simulation was carried by varying the amount of particles that went through the acclerating tube, varying the accelerating voltage, and the extraction voltage, from 50 to 3000 particles, from 30 kV to 150 kV, and from 1 kV to 10 kV respectively. The simulation results show that the ion extraction process and the ion beam formation at the ion source of ion implantor is very dependent on the geometry and the voltage of both electrode and the extractor on the device. The incorrect electrode geometry and voltage would cause the particle trajectory to be non-linear, while the angle of the beam would diverge too much. We’ve also found that the amount of simulated particle would affect the homogeneity of the cross section of the beam. The bigger the amount of the simulated particle, the more homogeneous and stable the beam becomes. Unfortunately, for 3000 particles the running process was very long and prone to errors. Therefore in this simulation, the amount of particles is set to 2000, which gave us a rather uniform beam cross section. The variation of extraction voltage 1 kV to 10 kV while keeping the accelerating voltage constant at 150 kV produced an increment of the diameter of the ion beam from 3.84 cm to 4.12 cm. The variation of accelerating voltage from 30 kV to 150 kV while keeping the extraction voltage constant at 10 kV caused the spot diameter of the ion beam to increase. The value of the spot diameter of the ion beam when the accelerating voltage is kept at 150 kV are 4.12 ± 0.05 cm and 4.05 ± 0.05 cm for y-axis and x-axis respectively.
A NOVEL DESIGN OF 17.5 KV HV FEEDTHROUGH FOR ARJUNA 2.0. A novel design of the 17.5 kV feedthrough for Arjuna 2.0 Cockcroft Walton generator has been proposed. It is used for connecting the output of RF transformer oscillator (in the outside of horizontal vessel) with the input of voltage multiplier (inside of horizontal vessel) of the Cockcroft Walton generator. It was equipped by covers on left and right side. The designed feedthrough was simple, compact, easy to manufacture, high performance to prevent flashover and also it was applied to Arjuna 2.0 Cockcroft Walton. It was made from teflon (PTFE) and solid copper, which have high dielectric strength, capable of withstanding press loads, and easy to manufacture. The shortest distance between grounding with conductor radially was 43.25 mm, and 253.5 mm for feedthrough surface. The design was verified by Finite Element Method software and continued with performance testing. According to simulation, the stress of voltage is high about 16 kV to 17.5 kV on feedthrough conductor and 0 to 3 kV on feedthrough flange. The electric field of the covered feedthrough is lower than the coverless feedthrough. The highest and lowest electric fields are 1.26 x 106 V/m and 1 x 105 to 2 x 105 V/m respectively. Furthermore, feedthrough has been tested up to 120 kV and no discharge occurred. It means this design can be operated for 17.5 kV and it was successful installed on Arjuna 2.0 Cockcroft Walton generator.
A modification of Boris Algorithm in cylindrical coordinate used to solve Lorentz equation for axisymmetrical plasma simulation is proposed. The velocity updates are calculated directly using matrix operation. The inertial forces are evaluated at n-0.5 time steps. The algorithm is tested for several scenarios: electric field only, electric field dominated, |E| = |B|, ExB drift, gyration test, and a test devised by Delzanno. The result is compared to the standard Boris solver in cylindrical coordinate. The results show that even though generally the solver is not that accurate compared to the standard Boris solver, especially for a larger time step width, it is comparatively faster. Thus, the solver might be useful for plasma simulations that do not require detailed trajectory for each simulated particle.
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