James K. Jones

The UK Extreme Photonics Applications Centre (EPAC) intends to flexibly provide laser-accelerated GeV-scale electrons to a wide array of experiments and like other such facilities must efficiently capture them from a laser-wakefield acceleration (LWFA) source. Here we describe a unique, modular beam capture optics system based on a FODO array of Halbach permanent-magnet quadrupoles and show how that modular arrangement can be used in different configurations to provide energy-selected and focused bunches for different purposes. We present an engineering concept for the beamline that incorporates diagnostics and drive laser extraction and describe the effect of field errors and misalignments and their mitigation.

Plasma-wakefield acceleration (PWFA) has attracted great attention due to its high accelerating gradients, which will drastically reduce the price, footprint, and carbon load of accelerators to be used for medical applications, free electron lasers (FEL), and future high-energy physics experiments. The Compact Linear Accelerator for Research and Applications (CLARA) at the Daresbury Laboratory is a state-of-the-art electron accelerator for a future FEL test facility, capable of producing 250 MeV electron bunches. Recently, a new beamline attached to CLARA, the so-called Full Energy Beam Exploitation (FEBE) facility, has been commissioned to provide ultra-short and low-emittance electron bunches. Here, we use the Fourier-Bessel Particle-In-Cell (FBPIC) code to investigate plasma wakefield acceleration (PWFA) with a two-bunch configuration at FEBE, aiming to double the energy of the witness bunch while preserving its incoming beam quality. Simulation results indicate that the driver's trailing portion is tightly focused by the transverse wakefield, leading to a surging beam density and a transition from the linear to the non-linear regime. An appropriate flattened wakefield due to beam loading is achieved assisted with the tailoring of the plasma density. Moreover, the impact of ramping plasma density on beam quality is also discussed.

Plasma wakefield acceleration revolutionized the field of particle accelerators by generating gigavolt-per-centimeter fields. To compete with conventional radio-frequency (RF) accelerators, plasma technology must demonstrate operation at high repetition rates, with a recent research showing feasibility at megahertz levels using an Argon source that recovered after about 60 ns. Here we report about a proof-of-principle experiment that demonstrates the recovery of a Hydrogen plasma at the sub-nanosecond timescale. The result is obtained with a pump-and-probe setup and has been characterized for a wide range of plasma densities. We observed that large plasma densities reestablish their initial state soon after the injection of the pump beam ( < 0.7 ns). Conversely, at lower densities we observe the formation of a local dense plasma channel affecting the probe beam dynamics even at long delay times ( > 13 ns). The results are supported with numerical simulations and represent a step forward for the next-generation of compact high-repetition rate accelerators.

The compact linear accelerator for research and applications (CLARA) is a 250 MeV ultrabright electron beam test facility at STFC Daresbury Laboratory. A user beamline has been designed to maximize the exploitation of CLARA in a variety of fields, including novel acceleration and new modalities of radiotherapy. In this paper, we present the specification and design of this beamline for full energy beam exploitation. We outline the key elements that will provide users access to ultrashort, low emittance electron bunches in two large experiment chambers. The results of start-to-end simulations are reported that verify the expected beam parameters delivered to these chambers. Key technical systems are detailed, including those which facilitate a combination of electron bunches with high-power laser pulses. Published by the American Physical Society 2024

The compact linear accelerator for research and applications (CLARA) is an ultrabright electron beam test facility being developed at STFC Daresbury Laboratory. The ultimate aim of CLARA is to test advanced free electron laser (FEL) schemes that can later be implemented on existing and future short-wavelength FELs. In addition, CLARA is a unique facility to provide a high-quality electron beam to test novel concepts and ideas in a wide range of disciplines and to function as a technology demonstrator for a future United Kingdom x-ray FEL facility. CLARA is being built in three phases; the first phase, or front end (FE), comprises an S-band rf photoinjector, a linac, and an S-bend merging with the existing versatile electron linear accelerator beam line; the second phase will complete the acceleration to full beam energy of 250 MeV and also incorporate a separate beam line for use of electrons at 250 MeV; and the third phase will include the FEL section. The CLARA FE was commissioned during 2018, and the facility was later made available for user experiments. Significant advancements have been made in developing high-level software and a simulation framework for start-to-end simulations. The high-level software has been successfully used for unmanned rf conditioning and for characterization of the electron beam. This paper describes the design of the CLARA FE, performance of technical systems, high-level software developments, preliminary results of measured beam parameters, and plans for improvements and upgrades.