The J-PARC Main Ring (MR) delivers high-intensity proton beams for the neutrino experiment. The beam intensity delivered to the neutrino experiment reached 520kW with a cycle time of 2.48 seconds in 2021. We chose to shorten the MR cycle time to 1.36 seconds to achieve higher beam intensity. An anode power supply feeds a high-voltage DC current to the tetrode vacuum tubes, which drive the RF cavity. Beam acceleration in a shorter MR cycle requires a higher RF voltage to keep the RF bucket large enough and a larger anode power supply current for the beam loading compensation. We plan to add RF systems to achieve higher RF voltage and to manage the output current of each anode power supply under limitations. To estimate the anode power supply current with a shorter MR cycle, we derived the beam loading compensation contribution in the power supply current using the data recorded during the operation with a cycle time of 2.48 seconds. We present the estimated anode power supply current for various combinations of RF voltage and the number of RF cavities.

> Tetrode vacuum tubes are used under the positive grid region > to accelerate a high intensity beam in the RCS. A tube amplifier is operated in push-pull mode and two tubes are installed in the amplifier. Although each control grid should be driven in counterphase for the push-pull operation, the waveform becomes asymmetric by the positive grid biasing. The vacuum tube operation analysis should include such an effect caused by the positive grid biasing. The analysis becomes complicated because the anode current and the control grid voltage waveforms interact each other under the heavy beam loading. The effects caused by the positive grid voltage are analyzed with the self-consistency. We will describe the analysis result under the positive grid biasing.

The longitudinal phase space tomography, which reconstructs the phase space distribution from the one-dimensional bunch profiles, is used in various accelerators to measure longitudinal beam parameters. At the J-PARC, an implementation of the phase space tomography based on the convolution back projection method has been used to measure the momentum spread of the injected beam. The method assumes that the beam distribution rotates without significant deformation during the synchrotron oscillation. Because of the nonlinearity of synchrotron motion with sinusoidal RF voltage, the method can be used only in limited situations such as small amplitude synchrotron oscillation. Algebraic Reconstruction Techniques (ART) in conjunction with particle tracking, which is implemented in CERN's tomography code, allows accurate reconstructions even for nonlinear large amplitude synchrotron oscillations. We present the overview of the application of CERN's tomography code to the J-PARC synchrotrons. The results of benchmarking are also reported.