PhD in development and optimization of the resonance and RF field controller for high duty-cycle operations of EuXFEL

Limited: 3 years | Starting date: earliest possible | ID: MDO009/2026 | Deadline: 27.08.2026 | Full-time/Part-time

DESY, with more than 2900 employees at its two locations in Hamburg and Zeuthen, is one of the world's leading research centres. Its research focuses on decoding the structure and function of matter, from the smallest particles of the universe to the building blocks of life. In this way, DESY contributes to solving the major questions and urgent challenges facing science, society and industry. With its ultramodern research infrastructure, its interdisciplinary research platforms and its international networks, DESY offers a highly attractive working environment in the fields of science, technology and administration as well as for the education of highly qualified young scientists.

The European X-ray Free Electron Laser (EuXFEL) is an X-ray laser facility driven by a superconducting linear accelerator. It is currently the brightest X-ray source of its kind, enabling unprecedented discoveries in the physical and life sciences. The EuXFEL High Duty-Cycle (HDC) upgrade will enable operation with long RF pulses (duty cycle above 10%) up to continuous wave (100% duty cycle), effectively increasing the number of produced X-ray pulses per second by an order of magnitude. This upgrade introduces first-of-its-kind challenges in controlling superconducting radio-frequency (SRF) cavities, specifically their RF field and frequency stability.

Building on previous achievements, the goal of this PhD project is to explore advanced control strategies to achieve the specified SRF cavity field stability (0.01% in amplitude and 0.01° in phase), despite their extremely narrow bandwidth (in the order of 10 Hz). In particular, the resonance controller for multiple cavities driven by a single source (MCAV) can be improved by introducing narrow-bandwidth active noise compensation. RF field feedback can be further enhanced by investigating variable-gain controllers that adapt to cavity detuning, or exploring other feedback algorithms. In addition, the MCAV approach can be optimized by leveraging information from all individual cavities, rather than relying solely on their vector sum, thereby enabling the development of a MIMO (multiple-input, multiple-output) controller. Furthermore, the limitations and potential benefits of increasing the RF pulse repetition rate beyond the currently proposed 1 Hz will be studied.

Beyond advancing state-of-the-art control techniques for particle accelerators, this PhD project has a clear practical objective: to define the optimal SRF cavity control approach for the HDC upgrade of EuXFEL, currently planned for the next decade

About your role:

• understanding and identifying the electromechanical accelerating cavity system
• designing, simulating, implementing, and testing novel system identification methods and control schemes at accelerator facilities and tests stands, on-site or at Helmholtz partner labs
• developing, simulating and testing of an improved RF field and resonance controller for SCAV (single-) and MCAV (multiple-cavity regulation scheme)
• exploring the possibility of making a combined resonance-field controller
• exploring options of increasing the pulse repetition rate beyond 1 Hz
• presentation of results at international conferences and publication in peer-reviewed journals are also expected

Good reasons to join:

Look forward to a unique working environment on our international research campus. Respectful cooperation and the well-being of our DESY employees are particularly important to us. Gender equality is an important aspect for us. To support work life balance we offer flexible working hours, variable part-time, job-sharing models and participation in mobile work (up to 50%). You will benefit from our family-friendly and collegial atmosphere, our established health management and occupational pension provision. As a public funded employer, we offer you a secure workplace and facilitate your individual career with our comprehensive training and development opportunities. Remuneration is according to the regulations of the TV-AVH. DESY offers its employees a financial supplement for a German job ticket (Deutschland-Ticket) at both locations.

Limited: 3 years

About you:

• Advanced knowledge in control systems and feedback theory
• Programming skills in high-level languages (Python, Matlab)
• Affinity with hands-on experiments is desired
• General knowledge in physics, particle accelerators and radio frequency systems is a plus
• Fluent in English
• Open to team work and external collaborations

For further information please contact Dr. Julien Branlard, julien.branland@desy.de at +49 40 8998-1599.

DESY in Hamburg does not grant doctoral degrees directly but collaborates with the TU Hamburg. Candidates for thesis research will have to satisfy the terms of admission for doctoral theses of the University of Hamburg. PhD students receive a monthly salary of 67% of the payment of the remuneration group 13 TVöD (Federal Government).

Please submit your complete application documents (letter of motivation, CV, relevant certificates and two letters of references) via our application portal.

We look forward to receiving your application via our application portal:

DESY promotes equal opportunities and diversity. The professional development of women is very important to us and therefore we strongly encourage women to apply for the vacant position. Applications from severely disabled persons will be given preference if they are equally qualified (sbv.desy.de).

You can find further information here:

https://www.desy.de/career/

Deutsches Elektronen-Synchrotron DESY

Personalabteilung

Notkestraße 85

22607 Hamburg

Phone: +49 40 8998-3392

Deadline for applications: 28.08.2026