Tribute to Frédéric Perrier (1961-2024)

A native of the Cévennes, Frédéric Perrier was born in Alès on 22 August 1961 and spent his childhood in Anduze (Gard).

  From 1981 to 1992: High energy physicist. After graduating from the Ecole Normale Supérieure (Ens Ulm, 1981S) and obtaining a Master's degree in Physics from the Pierre et Marie Curie University in 1982, he turned to nuclear and high energy physics. After obtaining his DEA in nuclear physics at the University of Orsay, he wrote his thesis1 at the Elementary Particle Physics Department of the Saclay Nuclear Research Centre (CEA) under the supervision of René Turlay, and defended it on 5 November 1986. The experiment was carried out at CERN under the aegis of the CDHSW collaboration, founded by Jack Steinberger (1921-2020) and directed from 1984 by Friedrich Dydak. The main figure of his thesis and the paper based on his work2 were presented by Jack Steinberger during his Nobel Lecture in 1988. The main result was that the mass of the top quark should be less than 240 GeV. This prediction was confirmed when the top quark was discovered in 1995 at Fermilab, Illinois, with a mass of 175 GeV. From 1986 to 1988, he was a postdoctoral fellow at the Stanford Linear Accelerator Laboratory (SLAC) at Stanford University, California, directed by Richard Taylor (1929-2018, Nobel Prize 1990). He developed a power laser for the polarised electron source to be installed in this accelerator3. After joining the CEA in 1989, he joined the ALEPH collaboration at the LEP electron-positron collider at CERN and participated in the search for the Higgs boson and the study of isolated photons in hadronic final states (thesis of Djamal Si Mohand, defended in 1994). At the end of 1990, he worked on a project for a large toroidal superconducting magnet detector for the future LHC collider4. This project was integrated as a central element of the ATLAS detector, one of the famous experiments where the Higgs boson was discovered in 2012.
 

    From 1993 to 2003: Geophysicist at the DASE (CEA). Wishing to devote himself to geophysics, he joined the Geophysics Laboratory (LDG) 5 at the CEA Bruyères-le-Châtel centre in 1993, at the invitation of Yves Caristan. From 1994, together with Jean-Philippe Avouac, he set up laboratory experiments in natural sites in France and in the Himalayas of Nepal. In rock mechanics, he carried out measurements of the electrofiltration coefficient in a triaxial loading cell, during deformation and up to fracture (thesis of Benoit Lorne, defended in 1997). He then worked on 3D electrical and electromagnetic modelling in complex heterogeneous media, to be applied to the natural sites studied (thesis of Sophie Hautot, defended in 1999). In natural sites, he set up a network of electrical measurements in the Sur-Frêtes pass near the Roselend dam (Savoie) and multidisciplinary instrumentation in a nearby tunnel. This experiment led to several spectacular observations (thesis of Michaël Trique, defended in 1998), such as the observation of large-scale electrical signals from electrofiltration due to changes in lake level and, with Jean-Christophe Sabroux and Patrick Richon, the observation of transient radon emissions associated with deformation transients6. In Nepal, he participated in the first ever magnetotelluric survey (thesis of Carole Lemonnier, defended in 2000), with partners from the University of Strasbourg7. In 2001, he joined Éric Pili's team at the Radioanalysis, Chemistry and Environment Laboratory of the DASE. A collaboration with the IPGP was then established through an experiment in the underground quarry of Vincennes (thesis of Catherine Crouzeix, defended in 2005). In 2003, he became Associate Professor (PAST) at the IPGP. In 2005, he was awarded the Habilitation à Diriger des Recherches and in 2006, he became Professor at Paris Diderot University and joined the IPGP.
 

    From 2004 to 2023: Professor at Paris Diderot University and researcher at IPGP. During his first years at the IPGP, he worked closely with Jean-Louis Le Mouël and Claude Allègre. In 2006, he resumed at the IPGP the collaboration with Nepalese institutions that he had started at the DASE. In 2007, together with Paul Tapponnier (1947-2023), he launched the thesis of Som Nath Sapkota (defended in 2011). He developed his own research on the relationship between CO2 emissions marked with radon at geothermal sites near the Main Central Thrust in Nepal, based on leads provided by Christian France-Lanord (CRPG). In 2007, significant metamorphic CO2 emissions were discovered, which he termed "tectonic fumaroles". These initial results8 led to the launch of major research projects, including the thesis of Frédéric Girault (defended in 2011). When he moved to the IPGP's new premises in rue Cuvier, he was able to develop, with the support of his CEA colleagues, along with Frédéric Girault and more recently Rémi Losno, all aspects of radon-222 and radium-226 measurements in the natural environment, including rocks, soil, water, biological samples and extraterrestrial samples. Since 2008, he has published numerous papers on the subject, the latest of which, on radon emissions from Martian and lunar meteorites, is dedicated to him9. In 2014, he founded the Physics of Natural Sites (PSN) team at the IPGP. Since 2015, his work on natural sites has focused on the consequences of the 2015 Gorkha earthquake (Mw7.9) in Nepal. This earthquake was one of the deadliest of the decade (>9000 casualties) and the largest in the Himalayas since the 1934 earthquake. To study this seismic crisis, he launched the thesis of Lok Bijaya Adhikari (thesis defended in 2020) with Laurent Bollinger and Jérôme Vergne. The discovery of eruptions of CO2 of crustal origin during, after and perhaps even before this earthquake was the culmination of more than twenty years of work in Nepal, years devoted to tracking gaseous phenomena associated with the seismic cycle10. He also launched two other theses by Nepalese students focusing on the Himalayas of Nepal, subsequently supervised by Frédéric Girault: on along-strike variations in metamorphic CO2 production, with Chiara Groppo and Franco Rolfo (UniTO), by Shashi Tamang (thesis defended in 2022), and on the geological sources of electromagnetic anomalies and sulphur emissions by Sandeep Thapa (thesis defended in 2023). At the same time, he resumed his research on underground sites in France. He was asked by François Bourges (GEConseil) to work on natural caves and the conservation of decorated caves, which recently led to the creation of GIS-GEMS. In particular, they reviewed 25 years of CO2 monitoring and the microclimatology of Chauvet Cave, showing for the first time that CO2 comes from surface sources and is sensitive to water infiltration11. More recently, he has developed his interest in the study of catchment areas and contaminated sites through various projects, and has also been interested in electrical networks and general theorems. His studies of elementary physical processes in natural sites have gradually led to the development of the discipline he has called "Physics of Natural Sites". He retired in August 2023. Frédéric Perrier has published more than 170 articles, and has been cited more than 6,000 times.

   A teacher with a big heart. During his career as a university lecturer, he has designed and taught more than 16 different courses at all levels (Bachelor, Master and Doctorate). All his students remember his clear, comprehensive and dynamic courses, and his desire to help them progress by getting the best out of each individual. As soon as he arrived at the IPGP, he took on trainees from the fourth year of secondary school, in groups of 5 pupils selected by the Paris Priority Education Department (Collège Clemenceau). These internships are based on an educational theme, with laboratory and field experiments. He was also involved in welcoming and supporting foreign students. In collaboration with Klaus Spitzer, he set up the French-German double master's degree in geophysics with the Bergakademie Technische Universität in Freiberg (TUBAF). Despite the difficulties caused by the pandemic, the first student graduated in 2023. He was particularly interested in the history of science, which he taught at doctoral level. In particular, he was a member of the Taton-Monge committee and organised a symposium in honour of René Taton (Paris, 2006), he founded the Monge committee for the publication of the complete works of Gaspard Monge and also published on Evariste Galois. More recently, he organised the "Women in Science" conference at the IPGP in 2018, on the occasion of the International Women in Science Day, with the support of Elisabeth Badinter and Roselyne Bachelot, and two colleagues, Laure Meynadier and Bénédicte Ménez. Numerous personalities from France and abroad came to present the women in science whom the symposium wished to honour.

   Sensitive and committed to traumatised children in disadvantaged countries. He worked with traumatised children12, particularly orphans from the 1994 Rwandan genocide. He gradually became interested in autistic children and began working with mentally handicapped children in Rwanda in 1998. From 2000 to 2001, while on sabbatical, he worked on a therapeutic mediation project for orphans of the Rwandan genocide in Ruhengeri, in the middle of a conflict zone near the border with Congo. His second home, Nepal, held a special place in his heart. Since 1993, he has been a regular teacher at the NAG school in Nepal, from nursery school to university entrance exam preparation. He founded the association Les Enfants du Népal in France in 1992. Since its official creation in 1998, he has been Vice-President of the Swiss Foundation Stiftung NAG Strassenkinder, based in Zurich, which since 1997 has financed the largest ongoing school and medical aid project in Nepal outside the framework of the United Nations.

 

 

   Frédéric Perrier's life and work are so rich that they are difficult to summarise, as his contributions cover so many fields and so many people. He had an unquenchable thirst for learning, spoke more than 8 languages, had recently obtained his black belt in Aikido, and had a vast knowledge of many scientific and cultural fields. He was an exceptional person, with a huge heart and a sincere and generous interest in all those who wanted to learn. He was against all forms of injustice and sometimes raised his voice to be heard, and rightly so. His sudden death on 21 November 2024 in Anduze leaves us speechless. He will remain an inspiration to us all. We will honour his memory by continuing his work, upholding his humanitarian commitments and sharing knowledge with passion.

 

1 Entitled "Precise measurement of the electroweak mixing parameter in neutrino scattering on iron nuclei", his thesis provides the most accurate measurement at the time of the sin2θw mixing parameter, a key parameter in the unified model of electromagnetic and weak interactions.

2 Abramowicz et al., Phys. Rev. Lett., 1986

3 MARKII collaboration, with the SLC electron-positron collider

4 Perrier, A LHC detector with open superconducting toroids, presentation at the LHC detector workshop, Bern, 11 June 1991

5 later integrated into the new Environmental Monitoring Analysis Department (DASE) created by Yves Caristan

6 Trique et al., Nature, 1999

7 Lemonnier et al., GRL, 1999

8 Perrier et al., EPSL, 2009
9 Girault et al., Sci. Rep., 2025
10 Girault et al., Nat. Comm., 2018
11 Bourges et al., STOTEN, 2020
12 Perrier & Nsengiyumva, Int. J. Sci. Ed., 2003; Perrier, in Cliniques du Jeu, La Pensée Sauvage, 2008