Linac4 H$^-$ ion source is required to deliver 50 mA of H$^-$ ions within a transverse rms emittance of 0.25π mm∙mrad[1, 2]. In order to meet these requirements, it is indispensable to clarify the H$^-$ ion extraction and beam formation process in the vicinity of the beam extraction hole i.e. extraction region in the H$^-$ ion source. In the previous works, the extraction region in the Linac4 H$^-$ ion source has been modeled by the 2D Particle in Cell (PIC)  method and 3D PIC method . In the Ref. , the extracted H$^-$ ion beam current and co-extracted electron current by the 3D PIC simulation has been compared with the experiments. However, the beam emittance calculated by the simulation model has not been directly compared with the experiments.
In order to compare the beam emittance with the experiments, we are now developing the integrated model of the source plasma, extraction region and acceleration region. As for the source plasma, the NINJA , which is 2D Electro-Magnetic-PIC (EM-PIC) code for the RF inductively coupled plasma has been applied. In the extraction region, 3D KEIO-Beam Formation and eXtraction (BFX) code has been applied to calculate the plasma meniscus and H$^-$ ion beam formation process. Finally, the IBSIMU and the TRAVEL-3D have been applied in the beam transport in the acceleration region to obtain the beam emittance.
We have performed the case of the positive ion extraction for the validation of the integrated model. It has been shown that the extracted positive ion current by the integrated model reasonably agrees with the experiment. In the presentation, we will show the case of the negative ion extraction, and the H$^-$ beam emittance and extracted beam current will be compared with the experiments.
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