This paper introduces a new approach to measure the muon magnetic moment anomaly a µ = (g − 2)/2, and the muon electric dipole moment (EDM) d µ at the J-PARC muon facility. The goal of our experiment is to measure a µ and d µ using an independent method with a factor of 10 lower muon momentum, and a factor of 20 smaller diameter storage-ring solenoid compared with previous and ongoing muon g − 2 experiments with unprecedented quality of the storage magnetic field. Additional significant differences from the present experimental method include a factor of 1,000 smaller transverse emittance of the muon beam (reaccelerated thermal muon beam), its efficient vertical injection into the solenoid, and tracking each decay positron from muon decay to obtain its momentum vector. The precision goal for a µ is statistical uncertainty of 450 part per billion (ppb), similar to the present experimental uncertainty, and a systematic uncertainty less than 70 ppb. The goal for EDM is a sensitivity of 1.5 × 10 −21 e • cm.

During the past five years, there has been an concerted program at SLAC and KEK to develop accelerator structures that meet the high gradient (65 MV/m) performance requirements for the Next Linear Collider (NLC) and Global Linear Collider (GLC) initiatives. The design that resulted is a 60-cm-long, traveling-wave structure with low group velocity and 150 degree per cell phase advance. It has an average iris size that produces an acceptable short-range wakefield, and dipole mode damping and detuning that adequately suppresses the long-range wakefield. More than eight such structures have operated at a 60 Hz repetition rate over 1000 hours at 65 MV/m with 400 ns long pulses, and have reached breakdown rate levels below the limit for the linear collider. Moreover, the structures are robust in that the rates continue to decrease over time, and if the structures are briefly exposed to air, the rates recover to their low levels within a few days. This paper presents a summary of the results from this program, which effectively ended last August with the selection of 'cold' technology for an International Linear Collider (ILC).

In X-ray focusing, grazing incidence mirrors offer advantages of no chromatic aberration and high focusing efficiency. Although nanofocusing mirrors have been developed for the hard X-ray region, there is no mirror with nanofocusing performance in the soft X-ray region. Designing a system with the ability to focus to a beam size smaller than 100 nm at an X-ray energy of less than 1 keV requires a numerical aperture larger than 0.01. This leads to difficulties in the fabrication of a soft X-ray focusing mirror with high accuracy. Ellipsoidal mirrors enable soft X-ray focusing with a high numerical aperture. In this study, we report a production process for ellipsoidal mirrors involving mandrel fabrication and replication processes. The fabricated ellipsoidal mirror was assessed under partial illumination conditions at the soft X-ray beamline (BL25SU) of SPring-8. A focal spot size of less than 250 nm was confirmed at 300 eV. The focusing tests indicated that the proposed fabrication process is promising for X-ray mirrors that have the form of a solid of revolution, including Wolter mirrors.

We demonstrate broadband focusing of multiple high-order harmonics of intense femtosecond laser pulses using an ellipsoidal mirror. The ellipsoidal mirror, with a high numerical aperture and a highly accurate surface, was fabricated using a replication process. The multiple high-order harmonics in the wavelength range between 10 and 20 nm were focused to the nearly diffraction-limited size of 350 × 380 nm2. According to Rayleigh's quarter wavelength criteria, the wavefront aberration of the focused beam was estimated to be less than 5 nm, which corresponds to a temporal dispersion of 16 as. The developed focusing system is suited for producing an intense attosecond laser field with negligible wavefront aberration, with which nonlinear light-matter interactions in the attosecond time domain can be explored.

Ellipsoidal mirrors are promising optical devices for soft x-ray focusing. A fabrication process consisting of master fabrication and replication has been developed to produce ellipsoidal mirrors with wide apertures of approximately 10 mm. In the present study, the focusing performance of an ellipsoidal mirror was evaluated using soft x-rays in the soft x-ray beamline BL25SU-a of SPring-8. The focus sizes were measured at photon energies of 300, 400, and 500 eV. A quantitative figure error of the ellipsoidal mirror was also evaluated by analyzing the wavefield of the focused beam retrieved using ptychography. The figure error distributions measured at different photon energies agreed with each other at a root mean square level of 1 nm. The developed focusing system can be used for various types of microscopy, allowing the use of a wide range of x-ray energies.