Description du sujet de thèse

BEAM MANIPULATION FOR NEXT-GENERATION COMPACT MULTI-STAGE AND MULTI-PHYS ACCELERATORS
Particle accelerator physics, photonic /laser
Laser-based accelerators, such as dielectric laser accelerators and laser-plasma accelerators, offer unmatched per innovative applications. However, the interaction between particles and the wave traveling through the medium is li centimeters, unlike conventional radiofrequency (RF) accelerators. Using multiple acceleration stages is one way to limitation, but it requires expertise in optical wave propagation and the transport of ultra-short particle beams. The this thesis will help define the conditions needed to design a hybrid accelerator that combines laser and RF acceler electron transport. It will rely on advanced simulation tools and experimental validation on prototypes like TWAC at way for a realistic future multi-stage setup accelerators are used in various fields, from fundamental physics to industry and medical applications. In conventional accelerators, charged particles are accelerated by a radiofrequency (RF) electromagnetic field traveling through waveguides at nearly the speed of light. As long as the particles stay in sync with the wave, they gain energy, similar to how a surfer rides a wave. While RF technology has become highly reliable, it's limited by electrical breakdown effects, restricting the acceleration gradient to about 100 MeV/m in the X-band (10–30 GHz). To overcome these limits, innovative acceleration techniques are being explored. Laser-plasma acceleration (LPA) and dielectric laser acceleration (DLA) are promising alternatives for future accelerators. They allow for miniaturizing structures down to centimeter scales while increasing energy gain. This compactness makes them suitable for applications in science, medicine (like radiotherapy), and industry, while also reducing infrastructure costs. Laser-plasma acceleration achieves gradients of several tens of GeV/m, far exceeding the 100 MeV/m of RF accelerators. A significant advancement demonstrated electron acceleration up to 10 GeV over 20 cm, confirming its effectiveness for high-gradient acceleration . These beams reduce the footprint of machines and produce ultra-short pulses, but at the cost of lower stability and beam quality, with higher energy spread and greater divergence.
Dielectric acceleration, as proposed in the exploratory TWAC EIC Pathfinder project, aims to overcome the challenges of stability and beam quality seen in other advanced acceleration methods. Unlike RF acceleration, which has been studied for nearly a century, and laser-plasma acceleration (LPA), which has been explored for over 40 years, accelerating electron bunches using THz-range fields in dielectric structures is a relatively new research topic. This interest is driven by recent progress in generating intense THz pulses for accelerator-based applications. The first experimental demonstration of electron acceleration in a dielectric using THz fields was published in 2015. Since then, other experiments have been carried out using different electron sources — such as at CLARA in the UK, and in China and the United States. The goal of this project is to propose a new multi-stage acceleration approach, aiming to design a hybrid accelerator. This would combine innovative techniques like dielectric waveguide acceleration and/or laser-plasma acceleration with conventional RF acceleration. The project's ambition is to guide the electron beam through a series of accelerating fields with different frequencies — from RF to the optical domain — to meet demands for energy spread, pulse duration, and compactness in acceleration length. To fully benefit from the strengths of each acceleration method, dedicated efforts are needed to manipulate and characterize the particle beam. Ultimately, the project aims to define the optimal arrangement of the various acceleration technologies (RF, laser-plasma, dielectric waveguide), balancing their respective advantages and limitations.

Contexte de travail

The PhD will be co-supervised between two laboratories: IJCLab (Orsay) and PhLAM (Lille). IJCLab will serve as the primary host institution, with regular research visits planned at PhLAM. The doctoral candidate will also participate in international conferences and collaboration meetings. Weekly meetings with the PhD student will ensure unified supervision, providing opportunities to discuss results and update research progress. The student will present their work within the European TWAC collaboration, and regular interim reports will contribute to the preparation of scientific publications and the final thesis manuscript. An annual monitoring committee will offer guidance on research direction and overall progress. IJCLAB bases its recruitment policy on the promotion of equality, diversity and inclusion. Essential values, they allow the professional development of agents, who are real actors in a collective success, but also the development of the laboratory itself.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.

Contraintes et risques

The experiments will take place in an environment involving lasers and ionising radiation, for which appropriate safety training will be required.

Informations complémentaires

The position is open to candidates with a strong interest in accelerator and laser physics, encompassing numerical simulations, experimentation, and data analysis. Applicants must hold a Master's degree in physics, engineering, or a related discipline. A solid knowledge of a programming language such as Python is essential. While not mandatory, familiarity with accelerator physics, optics, and/or photonics is a valuable asset. The ideal candidate should demonstrate a strong team spirit and a highly positive attitude towards collaborative work. Proficiency in spoken and written English is required. Applications must include: A detailed CV with no date gaps, clearly listing academic degrees, At least two references (people who may be contacted), A motivation letter, Master's (M2) or engineering school transcripts
The PhD will be part of the PHENIICS doctoral school at Université Paris-Saclay.