SuperKEKB is an electron-positron collider at the High Energy Accelerator Research Organization (KEK), which aims for a peak luminosity of 8.0×10³⁵ cm^－2 s^－1. In order to realize this high luminosity, the beam size at the interaction point is squeezed to ~50 nm in the vertical direction by the final focusing superconducting magnet system (QCS).When designing the QCS system, 3D simulation and optimization of the support system were carried out given the presence of external magnetic field and vibration. The simulation results were compared with measurements. In this paper, some examples of simulation results, such as structural analysis and vibration analysis are shown.

In this paper, some numerical results for advection phenomenon are shown based on the FEM (Finite Element Method) using bubble function element. As the governing equation, the advection equation is employed, and the finite element method using the bubble function element is applied to discretize the governing equation. In addition, the stabilization control term is introduced in the finite element equation, and effect of the stabilization control term is shown in this paper.

The development of linear IFMIF prototype accelerator is underway with international collaboration between EU and Japan. The RFQ was installed in 2016 and first hydrogen beam was accelerated in July 2018. The beam current was increased up to the nominal value (~60 mA), and the first D-beam acceleration was done in March 2019. At present, the D beam experiment is continued aiming 125 mA at 5 MeV using a beam dump for short pulse mode (1 ms pulse, 0.1% duty cycle). In parallel, the assembling of the SRF linac which will be installed at the downstream of the RFQ linac is underway. The CW beam dump was already installed. The activities for CW operation will be started in 2020.

The rapid cycling synchrotron (RCS) of the J-PARC is a high-power pulsed proton driver aiming for a 1-MW beam power. The most important issues in realizing such a high-power beam operation are controlling and minimizing beam loss to maintain machine activations within permissible levels. In the RCS, numerical simulations played a vital role in isolating beam loss mechanisms and finding their solutions in combination with actual beam experiments; various ideas for beam loss mitigation were proposed with helps of the numerical simulations, and verified by experiments. As a result of such continuous efforts including several hardware improvements, we have recently accomplished a 1-MW beam acceleration with considerably low fractional beam loss of several 10⁻³. This report presents our beam dynamics approaches to beam loss issues that we faced in a series of high-intensity beam tests of up to 1 MW.

I stayed at Synchrotron SOLEIL in France for 10 months, using the support program for long-term research abroad of KEK. I joined in the Accelerator Physics group. I investigated for the collective beam effects concerning harmonic RF cavities.