SuperKEKB is a positron-electron collider with a nano-beam scheme and continues to achieve the world’s highest luminosity for the production of B meson pairs. The luminosity performance has been improved by the adoption of the crab-waist scheme. The nano-beam scheme allows the vertical beta function at the interaction point (IP) to be much smaller than the bunch length. The vertical beta function and the beam size at the collision point are the smallest in the world among colliders. As the result, the peak luminosity which is larger than twice the predecessor KEKB record has been achieved in 2022. Recent progress will be presented, and then the problems and issues to be overcome will be discussed for further improvement of the luminosity performance. We had a long shutdown (LS1) since 2022 summer to upgrade both the Belle II detector and the machine. We will report the strategy of luminosity improvement after LS1.

The environmental credential of future colliders are increasingly in the spotlight, because of their size and complexity, and will be under scrutiny for their impact on the climate. Therefore, sustainability has become a prioritized goal in the design, planning and implementation of future accelerators; approaches to improved sustainability range from overall system design, optimization of subsystems and key components, to operational concepts. A direct quantification of the ecological footprint, be it greenhouse gas emissions during construction and operation, or consumption of problematic materials, is currently performed only sporadically, mostly through translation of electricity consumption into equivalent CO2 emissions. Two large electron-positron linear colliders are currently being studied as potential future Higgs-factories, CLIC at CERN and ILC in Japan. These projects are the central elements of the recently approved EU / EAJADE (Europe-America-Japan Accelerator Development and Exchange) program. A direct societal impact is expected through EAJADE WP4 (Sustainable Technologies for Scientific Facilities), where methods to reduce the power consumption of accelerator technologies and systems will be studied, and smart integration of future accelerator infrastructure with the surrounding site and society (e.g. Green ILC concept). This contribution will highlight past achievements and address the EAJADE WP4 future program.

​A novel technique, called a spin transparency mode, for preservation and control of electron and ion spin polarization in colliders and storage rings has been proposed. The beam polarization can then be fully controlled by small adjustments of the snake axis orientations and snake strengths. An experiment has been carried out recently to test the concept. One of the RHIC rings is set to be “transparent” to the spin by making the axes of its two Siberian snakes nearly parallel. The polarization was rotated from vertical to radial and from up to down by varying the snake currents. This paper summarizes the recent experiment results and discusses the comparison with simulations.