EPAC

The first experimental area (EA1) will be configured as a fixed geometry, long focus beamline, primarily for generating electron beams in gas targets through laser-wakefield acceleration (LWFA).
The higher repetition rate compared to the CLF’s Gemini laser facility will enable large-scale parameter scans and the use of automated optimisation routines to study LWFA physics, producing high quality electron beams in the multi-GeV energy range. LWFA-based radiation sources with unique properties will provide a resource for a wider community of users to perform advanced techniques, for example X-ray absorption spectroscopy with femtosecond time resolution. The enhancement in accelerator performance that will be realised with EPAC will enable the application of these secondary sources for industrial inspection, biological imaging and security scanning.

EA1 divides into two sections: the Source Area (EA1-S, 21m x 10m) and the Applications Area (EA1-A, 20m x 9 m). EA1-S can hold a focusing optic up to 14.3m focal length (f/65), that will generate an intensity above 5 x 1018 Wcm-2 with the 1PW laser pulse. At the end of the project, the layout in EA1-A will have essential diagnostics to characterise preliminary LWFA-generated electron beams. During facility commissioning and early operational periods, non-invasive electron diagnostics will be introduced to allow monitoring of beams while they are being used for applications.
The facility will provide a range of gas targets, designed and maintained by STFC, and will also be able to field specialist targets when requested by facility users. Diagnostics for the accelerator will be built as a permanent infrastructure, providing reliable short pulse optical probing of the plasma. The primary electron beam magnets are being designed by the STFC Accelerator Science and Technology Centre (ASTeC) to control divergence and accurately measure the energy spectrum.
While we intend to maintain the focusing beamline in a fixed configuration, the layout inside the target chamber and in EA1-A will be flexible and arranged according to user requirements. Components will be modular and portable so that different arrangements, including specialist rigs brought from users’ institutes, can be deployed easily and quickly. This will enable a diverse range of objectives, covering all types of access from fundamental plasma physics experiments to industrial CT scanning.

EA2 has been designed as a flexible experimental area capable of undertaking laser-matter interactions with both short (f/3) and long focus (f/35) geometries. The primary aim of EA2 will be to deliver high intensity solid target interactions; however, it will be possible to also deliver liquid and gas targetry, depending on the science or application driver. By the end of the project, the large-scale infrastructure for the area will be delivered, namely the interaction chamber, adaptive optic (AO) chamber and some supporting beam transport. The design of EA2 permits a range of experimental configurations with the single 10Hz, 1PW beam, but also has the capability to include a second, high power beamline and multiple optical probes, should these become available as part of a future facility upgrade.

The design of the interaction chamber and complementary diagnostics will allow users to study high energy density states of matter, as well as produce a range of high-energy particle and photon beams for scientific or industrial applications. A number of targetry systems will be used in the EA2 interaction chamber, including gas cells, tape drive, liquid jets, cryogenic targets and multi-component complex targetry arrays. While some plasma and post-interaction diagnostics will be located in the interaction chamber, it is planned that most secondary-source diagnostics be housed in additional chambers that can be attached to the main interaction chamber as required.
A primary science driver for EA2 will be ion acceleration, where the high intensities coupled with high repetition rate will create a cutting-edgecapability for studying the fundamentals of the various ion acceleration mechanisms, as well as optimising these sources for a range of scientific and industrial applications. These sources will be spectrally and spatially characterised by active ion diagnostics, the development of which is currently underway. Once the production of such sources has been established, schemes could be developed to transport laser-generated ion beams within the target area, to provide enhanced energy selection or collimation for a range of applications, including radiobiology or radiation hardness testing. High flux beams of neutrons will also be produced in EA2, most likely via a pitcher-catcher set-up.
With the addition of a second beamline as part of a facility upgrade, multi-beam interactions will be possible (for example, a second petawatt-class beam or lower energy auxiliary beam). These could be performed in dual short-focus mode, or short-long focus mode. The target chamber has been sized sufficiently to accommodate the required beamline optics, as well as the typical (most commonly used at present) post-interaction diagnostics.