The quarter wave resonator (QWR, a.k.a. λ/4 resonator) for the new ISIS MEBT is a bunching cavity that longitudinally compresses the H- beam into smaller bunches. It has two gaps with a distance of βλ/2 between mid-gaps, and works in π mode at the resonant frequency of 202.5 MHz, with a phase angle of -90 degrees, and a maximum voltage per gap (E0L) of 55 kV. The detailed RF and thermal design were developed, followed by the manufacturing and testing of a prototype, all presented elsewhere. Parts for 5 new cavities were later manufactured, whose details were also presented elsewhere. This paper discusses how these new cavities were assembled, tuned and tested. The assembly was done in the metrology lab to ensure the correct alignment of the nose cones to the stem ring, with the subsequent doweling. Unexpected problems were also found, including the installation of the automatic tuner finger strips, how to achieve the expected quality factor and the conditioning of the cavities to cope with multipacting.

There is increasing global interest in developing high-power neutron spallation sources. ISIS, as one of the leading facilities in this field, aims to upgrade its existing 800 MeV, 200 kW accelerator to a next-generation machine delivering 1–2 GeV beam energy and 1–2 MW power. Several upgrade scenarios are under consideration, including RCS, ACS, and FFA-based concepts. In all cases, a 500 MeV injector linac is required as the first stage of the accelerator complex to meet broad operational objectives. A central design goal is to maximize system sustainability, reliability, and maintainability under high-power operation. Comparative studies indicate that, with suitable cavity design innovations, a normal-conducting (NC) linac can provide greater long-term sustainability and operational robustness than superconducting RF (SRF) technology within this energy range. However, for configurations such as an accumulator ring scenario reaching 1.8 GeV, the injector linac can be extended with additional medium- and high-beta SRF cavities to achieve the target energy while maintaining high efficiency. This paper presents the overall linac design concept, discusses the main design parameters, and summarizes the results of beam dynamics simulations supporting the proposed upgrade path for the ISIS high-power spallation facility.

The Fixed Field Alternating Gradient (FFA) accelerator is a natural candidate for a high-power pulsed proton driver, although no high-power FFA has yet been constructed. As a critical component of the accelerator, the main magnets have been the subject of particular study. Operational flexibility, in terms of machine optics, over a large range is an essential feature of such a machine. In order to explore this in more detail a dedicated FFA prototype magnet has been designed and manufactured. This magnet was manufactured and delivered to the Rutherford Appleton Laboratory (RAL) in the UK in April 2025, and field measurements are subsequently planned to establish its characteristics. This paper will discuss the design, manufacture, and measurement plans of the prototype magnet.