arXiv subjects

Tetsuya Kobayashi

Publications and source records attributed to Tetsuya Kobayashi.

3 recordsLinked to original sources

arXiv2025

Study of laser-beam arrival time synchronization towards sub-picosecond stability level

A precise synchronization between laser pulse and electron beam arrival time is essential for achieving sub-picosecond stability in modern accelerator facilities. In this work, a Low-Level RF system architecture combined with White Rabbit based timing system has been tested through a collaboration between KEK (Japan) and CNRS/IN2P3, IJClab (France). The setup combines a frequency standard generator, an IDROGEN carrier board with an embedded White Rabbit node, and SkyWorks synthesizers of different form factors to distribute phase-locked clock signals over telecommunication fiber. Phase noise power spectral density measurements were performed at several RF sub-harmonics to confirm synchronization performance. These results demonstrate the feasibility of implementing the White Rabbit-IDROGEN synchronization scheme for large-scale accelerators, including applications to laser-based diagnostics.

physics.acc-ph↗

arXiv2025

Omics-scale polymer computational database transferable to real-world artificial intelligence applications

Developing large-scale foundational datasets is a critical milestone in advancing artificial intelligence (AI)-driven scientific innovation. However, unlike AI-mature fields such as natural language processing, materials science, particularly polymer research, has significantly lagged in developing extensive open datasets. This lag is primarily due to the high costs of polymer synthesis and property measurements, along with the vastness and complexity of the chemical space. This study presents PolyOmics, an omics-scale computational database generated through fully automated molecular dynamics simulation pipelines that provide diverse physical properties for over $10^5$ polymeric materials. The PolyOmics database is collaboratively developed by approximately 260 researchers from 48 institutions to bridge the gap between academia and industry. Machine learning models pretrained on PolyOmics can be efficiently fine-tuned for a wide range of real-world downstream tasks, even when only limited experimental data are available. Notably, the generalisation capability of these simulation-to-real transfer models improve significantly as the size of the PolyOmics database increases, exhibiting power-law scaling. The emergence of scaling laws supports the "more is better" principle, highlighting the significance of ultralarge-scale computational materials data for improving real-world prediction performance. This unprecedented omics-scale database reveals vast unexplored regions of polymer materials, providing a foundation for AI-driven polymer science.

physics.chem-ph↗

arXiv2018

A New Damper for Coupled-Bunch Instabilities caused by the accelerating mode at SuperKEKB

SuperKEKB is an asymmetric electron-positron circular collider based on nano-beam scheme at interaction region and large beam current. Large beam current makes growth rates of longitudinal coupled-bunch instabilities (LCBI) large. Especially some lowest modes near accelerating frequency are serious. On the design parameter for SuperKEKB, $μ$ = -1, -2, -3 mode of LCBI can be destabilized. We developed new LCBI damper to suppress newly arisen LCBI modes ($μ$ = -1, -2, -3) in SuperKEKB. The new damper will be installed in Low Level RF control system. The new LCBI damper is independent of main LLRF control components. In the test bench measurement, our new LCBI damper has good performance and satisfied required specifications. For preparation of using LCBI damper, we produced the simulation of beam oscillation damped by RF feedback. The results of this simulation shows that we need more dampers than them we prepared. We report profile of new damper and results of test bench measurement and feedback simulation in this paper.

physics.acc-ph↗