The Research Trimester (RT) of the Particles, Nuclei and the Universe (PNU) domain
An internship dedicated to the study of high energies
High-energy physics, a branch of physics that studies elementary particles, which are the smallest components of matter, as well as the fundamental forces that govern them, is making major advances and generating countless applications. The standard model of particle physics describes fundamental particles and their interactions, while the concordance model of cosmology explains the evolution of the universe by integrating dark matter, dark energy and cosmic expansion. Together, these models form a solid theoretical framework that allows for the accurate prediction of many phenomena, from elementary particles to the large structures of the universe. These issues, at the crossroads of conceptual and technological challenges, make high-energy physics a crucial field with cultural, societal and economic implications.
In this context, the UNP TR at Mines Paris – PSL allows second-year engineering students to explore these issues through immersion in cutting-edge research laboratories. The aim is to provide them with the essential theoretical foundations, to enable them to apply the knowledge they acquired in the first year, and to introduce them to the specialized teaching of the third year. This term also aims to illustrate the impact of fundamental physics on society and its concrete applications.
Spotlight on a 2025 student project
Trapped ion spectroscopy: improving the stability of an optical signal
As part of the PNU Research Quarter, Yannis Baron and Matti Comba, engineering students at Mines Paris – PSL, joined the Kastler Brossel Laboratory (LKB) to work on an ultra-precise measurement technique using trapped ion spectroscopy. Their objective was to ensure the transmission of a very precise frequency optical signal through a 200-meter optical fiber without loss of coherence. This signal functions as an ultra-stable clock for scientific experiments, but it can be slightly distorted by tiny disturbances called phase noise, a bit like interference that scrambles a radio message. By controlling this interference, their work contributes to refining essential measurements in physics, particularly to better understand the fundamental properties of matter.
The students developed an experimental device for evaluating and correcting the phase noise introduced by the fiber, by identifying the sources of disturbance, particularly the temperature variations in the laboratory. Using both theoretical concepts and experimental tools (such as lasers, light sensors and devices that modulate light waves), they improved a system capable of correcting signal disturbances. This device will soon be installed to guarantee even more reliable transmission of the ultra-precise signal delivered by the REFIMEVE network, a research infrastructure that transports extremely stable time and frequency references via optical fibers, serving scientific research in France and Europe.
Laurent Hilico, professor at the University of Évry Val d’Essonne (Paris-Saclay) and researcher at the Kastler Brossel Laboratory, praises the quality of the work carried out:
An excellent internship in every respect (human, understanding of physics, achievements, etc.) which has led to a final assembly that will soon be installed at the output of the extraction station of the ultra-stable signal delivered by the REFIMEVE network.
The project led by Yannis Baron and Matti Comba illustrates the value of the Research Quarter: it is an immersive learning experience for the students, coupled with a concrete and lasting scientific contribution. By improving the transmission of optical reference signals, their work paves the way for experimental advances in spectroscopy and metrology.
Three questions for Yannis Baron and Matti Comba:
Why was this project important and what were the scientific issues at stake?
In the experiment led by Mr. Hilico, lasers are used to take measurements on an ion trap. The aim of the experiment is to refine the measurement of the ratio between the mass of the proton and that of the electron in order to take measurements on an ion trap and achieve a new record precision of 10−12.
This measurement is part of the international CODATA project, which aims to improve our knowledge of the fundamental constants of physics. In fact, this improvement in the precision of our measurements would eventually allow us to test models beyond the standard model of physics. Our system was therefore used to better control the precision of the experiment’s lasers in order to achieve a new record of precision in the long term!
How did you set up and test your device?
Using scientific documentation provided by Mr. Hilico, we were able to set up a test device that we assembled element by element. For each element assembled, we made sure that the signal obtained met our expectations and took all the necessary power measurements to leave nothing to chance. After trying out an initial experimental set-up, we set up a second, more efficient one to take phase noise measurements via the generated correction. To take our measurements, we launched an acquisition program that could run for up to two whole weeks.
Once the experimental device had been tested on several lengths of fiber, we designed a more condensed model that we were able to assemble at the end of our internship.
What are the prospects for the application of your work?
Our work has enabled the installation of a new element in the cabinet of the REFIMEVE extraction station. The system we have built will eventually be reproduced in triplicate to serve the needs of several experiments at the LKB and at LERMA, a neighboring laboratory. Thanks to this device, we have succeeded in significantly reducing the phase noise induced by the optical fibers and thus enable the continuation of Mr. Hilico’s experiment, which aims to achieve a new record of precision in the measurement of the mp/me ratio of the order of 10−12. It also allowed us to observe that the phase noise in the fibers is more than significant and that it is therefore necessary to consider compensating it over as many fiber sections as possible.
Past projects: a research internship serving the long term
The Trimestre Recherche (TR) internships are not only a scientific immersion for the students of Mines Paris – PSL: they are part of a long-term research dynamic for the laboratories that host them. By integrating ambitious projects, the engineering students make a concrete contribution that extends well beyond the few months of the internship. It is in this context that Camille Desvigne, a student at Mines Paris – PSL, completed an internship at the Institute of Astrophysics of Paris (IAP), under the direction of Professor Brigitte Rocca Volmerange, in 2022-2023. His subject? The study of the photometric evolution of galaxies up to the dark ages of the universe, which consists of analyzing how the light emitted by galaxies has changed over time, going back to a very ancient era when the universe was still young and devoid of major light sources. This research was conducted in direct connection with the Euclid space mission.
Understanding the evolution of galaxies through photometry
One of the great challenges of astrophysics is to trace the appearance of the first galaxies in the universe. These immense collections of stars, gas and dust formed gradually, marking the end of the dark ages, a period following the Big Bang when the universe, still filled with neutral gas, was almost devoid of visible light. To study this transition, scientists use photometry, a technique that measures the intensity and color of light emitted by celestial objects and received through the filters of telescope cameras. By analyzing these light variations, they seek to understand how and when galaxies emerged and began to illuminate the universe.
To answer these questions, researchers rely on theoretical models and observations made by space telescopes such as the James Web Space Telescope (JWST) and Euclid. The objective of Camille’s internship was to model the evolution of galaxies using a specific computer code: Pegase (Programme d’Étude des Galaxies par Synthèse Évolutive). Developed by the astrophysicists in charge of the internship and published in 2019 in the journal Astronomy & Astrophysics (A&A) to model the evolution of galaxies over time, it simulates the way in which stars, gas and dust evolve and interact on the scale of a galaxy and how these interactions influence the light emitted, taking into account parameters such as the formation of stars, their evolution and their extinction.
