Multi-staging scenarios of plasma modules at CLARA FEBE

Charged particle beams and high-power laser pulses can drive electric fields orders of magnitude larger than those generated in cupper-based cavity resonators. Although this is paradigm shifting, staging of multiple plasma modules remains a key component to be developed and optimised for the scalability of plasma-based technologies. There are many technological challenges to be addressed such as whether emittance and energy spread, and hence six-dimensional phase space be preserved simultaneously through stages. Once achieved, this will unleash applications including compact X-ray FELs with stringent beam quality requirements.

Dr Apsimon previously developed a method for staging of orthogonally located THz driven dielectric lines waveguide structures. The method included pseudo-inverse matching between stages with second order corrections using non-periodic transfer matrix. This is followed by determining parameters for the best and shortest lattice among various lattices using multi-objective optimisation. This method will be consolidated and implemented for capillary staging at FEBE.

FEBE at CLARA has been designed to facilitate a variety of novel accelerator experiments. It is capable of delivering kA beams with bunch length at the order of 100 fs and a radius of 100 μs at 250 MeV. It is equipped with a mask array located at high dispersion region of the arc connecting FEBE to main CLARA beamline for variable longitudinal bunch shaping. This allows manipulation of a single bunch to create driving and trailing beams. Housing a 250 MeV high quality electron beam and a 100 TW laser at two experimental chambers, FEBE provides the perfect experimental environment to develop plasma-based accelerator technologies.

In this project, the student will numerically study the integration of a discharge-based capillary plasma source within the FEBE hutch including configurations of beam optics before and after plasma to achieve matching into the plasma and preserving beam quality after plasma. These will constitute the basic building blocks to explore a variety of multi-staging scenarios at FEBE.

Proposed Scheme of Work

Year 1 The student will follow the CI Lecture series to learn especially beam dynamics and plasma acceleration whilst establishing a good knowledge of the relevant literature. In this year, they will familiarise themselves with an arsenal of accelerator (GPT, MADX, OPAL) and plasma codes (EPOCH, WarpX, HiPACE++) coherently with other members of Manchester accelerator group. They will develop a framework interfacing an accelerator and a plasma code to achieve start to end simulations of FEBE hutch with an integrated plasma module allowing systematic studies.

Year 2 The mask for longitudinal shaping will create a different beam distribution for drive and witness beam depending on where it is sampling on the main CLARA bunch. Student will investigate different drive and trailing beam distributions available by the mask and their propagation through a 10 cm long capillary plasma module. They will also investigate the performance of the module through systematic studies as a function of plasma density, radius and gas mixture. In this year, the student will study the pre- and post-plasma optics by configuring existing components and identifying any additional optics required. They will characterise the beam at the FEBE post hutch section and identify the spectrometer resolutions required for different beam distributions studied. By the end of this year, they will deliver a strategy for integration of a 10 cm plasma in the FEBE hutch including plasma and beam characteristic, pre- and post-plasma optics.

Year 3 In this year, student will conceptually explore a combination of layouts for staging plasma modules. The main problem is the beam quality degradation after the first stage preventing the driver to induce plasma wakefields in the second stage. Hybrid options to mitigate this can be one or both driver electron bunches generated by LWFA and externally injected into capillary targets. For example, these additional drivers can be generated by splitting FEBE laser and directing it on gas-jet targets. Staging optics will be explored using multi-objective optimisation of lattices. The student will investigate conventional quadrupoles and plasma lenses for these matching sections.

Year 4 The highlights of the above studies will be written up as a PhD thesis. A number of manuscripts for journal articles will be completed across Y3 and Y4.