Ilario Boscolo, who was one of the proponents of the AEgIS experiment at CERN, passed away on 16 April 2024 at the age of 84.

Ilario Boscolo was born in Codevigo, Italy in 1940 and graduated from the nearby University of Padua. In 1968 he joined the University of Lecce, where he initiated research in accelerator physics, high-intensity electron beams and free electron lasers (FELs), and far-infrared and CO₂ lasers. Among his important scientific contributions at that time were the development of a prototype electrostatic accelerator, investigations on far-infrared lasers optically pumped in a cavity, and a much-cited theoretical proposal for a two-stage FEL for coherent harmonic amplification (an optical klystron). Ilario spent long periods of study in international research institutes, including the ENEA fusion energy centre in Frascati and the University of California Santa Barbara, where he collaborated with world-leading FEL researchers Luis Elias and William Colson.

In 1987 Ilario was called to the University of Milan, where he became full professor, to participate in the INFN project ELFA (electron laser facility for acceleration) and was responsible for the photocathode emission. His interest then turned to other topics, including efficient electron sources based on field emission from carbon nanotubes or ferroelectric ceramics and, within CERN, pulsed laser phase coding systems for new acceleration facilities. Within the INFN SPARC–SPARX initiative, started in 2003 and based in Frascati, he focused on laser applications for the development of pulsed, high-brightness UV and X-ray FEL sources. In particular, he showed that the high beam quality of the electron sources depends on suitable shaping of comb laser pulses, the study of which was realised in a dedicated laser laboratory at Milan founded by Ilario.

In 2007 Ilario was one of the proponents of the AEgIS experiment at the CERN Anti­proton Decelerator, which aimed to investigate the properties of antimatter, in particular its gravitational interactions. This required the production of a low-energy beam of antihydrogen atoms, obtained by a charge-exchange process with positronium atoms laser-excited at Rydberg levels. Led by Ilario, the Milan laser laboratory was responsible for the laser system that was required to make this pairing possible. AEgIS demonstrated the first pulsed-production of antihydrogen atoms in 2018, enabling a series of antimatter studies that are ongoing.

In all his activities, Ilario showed great passion and enthusiasm for both science and its applications. This positive attitude was also widely displayed through his didactical activity in various courses at the University of Milan. He was responsible for a new physics laboratory for the biology programme and for the laser laboratory for the physics programme. In addition, his greatest success was the complete reconstruction of the general physics laboratory for first-year students. By encouraging students to practice and elaborate on their own, with only little guidance from the teacher, this laboratory left an indelible mark on their training as physicists.

Another strong passion of Ilario was civil commitment, reflected in his constant engagement with university governance and studies of politics and economics, to which he dedicated himself with his usual inexhaustible enthusiasm, particularly after his retirement.

Ilario is remembered by his collaborators and students as a person of great culture, of brilliant insights, of a willingness to discuss physics and politics with anyone, and as an exquisite friend. He was a true scientist, leaving a deep mark on physics and a bright memory for everyone who had the honour of knowing him.

Renowned experimental physicist and co-initiator of relativistic heavy-ion physics, Rudolf Bock, passed away on 9 April 2024 aged 96.

Rudolf Bock was born in Mannheim, Germany in May 1927 and obtained his diploma in physics from the University of Heidelberg in 1954. He conducted his doctoral thesis on deuteron-induced nuclear reactions at the cyclotron of the Max Planck Institute for Medical Research in Heidelberg and received his doctorate from Heidelberg University in 1958. He then investigated nuclear reactions at the newly founded MPI for Nuclear Physics (MPIK) at the tandem accelerators there, initially with light ions and from 1963 with heavier ions.

In 1967 he was appointed full professor at the University of Marburg and was involved in the development of a joint accelerator project for heavy-ion research, ultimately leading to the UNILAC accelerator project. On 17 December 1969, the research centre GSI (Gesellschaft für Schwerionenforschung) was founded in Darmstadt–Wixhausen. As one of its founding fathers and subsequently as a long-standing member of the GSI board of directors, Rudolf Bock played a decisive role in the development of nuclear physics with heavy ions. At the same time, he maintained his contacts with Heidelberg as an honorary professor and as an external scientific member of the MPIK. In 2000 he was awarded an honorary doctorate from Goethe University Frankfurt.

Research with relativistic heavy-ion beams soon led to great successes. From 1974 Rudolf Bock established a working group at GSI under the leadership of Hans Gutbrod and Reinhard Stock, who set up and successfully carried out two major experiments at the Berkeley Bevalac accelerator. These resulted in the discovery of compressed, hot nuclear matter with hydrodynamic flow behaviour and thus formed the basis for his later experiments on quark–gluon plasma at CERN.

From the mid-1980s, the heavy-ion synchrotron SIS18 was set up at GSI under the leadership of director Paul Kienle. Thanks to Rudolf Bock’s guidance and in cooperation with surrounding universities, three new experiments (FOPI, KAOS and TAPS) were created, which focused on the formation of compressed nuclear matter as well as on hadron production and in particular the formation of light atomic nuclei. Around the same time, he was working on plans for experiments at much higher energies, which could ultimately only be realised at the CERN
SPS accelerator, with decisive contributions from GSI and LBL Berkeley. This led to the development of today’s global programme in ultra-relativistic nuclear–nuclear collisions, which has been pursued since the 1990s at the AGS and SPS, from 2000 with four experiments at RHIC and, since 2010, has been led by ALICE at the LHC at the highest energies.

The cooperation between GSI and LBL Berkeley was not only the beginning of relativistic heavy-ion physics. Supported by Hermann Grunder, then head of the LBL accelerator department, Rudolf Bock started the inertial confinement fusion programme in Germany. He also laid an important foundation for ion-beam therapy by supporting the secondment of Gerhard Kraft from GSI to the cancer-therapy programme at LBL. After his retirement in December 1995, Rudolf Bock maintained his scientific activities at GSI, his primary interest being the development of experiments on plasma physics and inertial-confinement fusion with high-intensity ion and laser beams.

Throughout the course of his scientific career, Rudolf Bock established numerous new research collaborations with institutes in Germany and abroad. As he himself had taken part in the Second World War and had spent several years as a prisoner of war in Russia, the idea of international understanding and peacekeeping was an important concern for him. As early as 1969 he invited many Russian scientists to the nuclear-physics conference at MPIK, and from the 1970s he promoted many collaborations between GSI and Russian institutes. He also pushed for Russia to become the largest member state in the GSI/FAIR project. The Russian invasion of Ukraine in February 2022 was therefore a great disappointment for him and for all of us.

Rudolf Bock was regularly present at GSI until his last days and continued to take an interest in current research and developments on campus. His advice and foresight will be sorely missed.

Theoretical physicist Werner Rühl died on 31 December 2023 in Füssen, Germany at the age of 86.

He was born in 1937, at a time when theoretical physics in Germany was being destroyed by the Nazis. After the Second World War, the ongoing study of cosmic rays and the availability of higher energies from accelerators made particle physics the most interesting field for budding researchers like him. Part of the way ahead was obvious: learn from the US and profit from the new spirit of European unity embodied by the creation of CERN.

Rühl followed this path in the straightest possible way. He obtained his PhD in 1962 in Cologne and became a research associate at CERN in 1964. Two years later he took up a postdoc at Rockefeller University, New York, before returning to CERN as a staff member in 1967, and obtained a chair in 1970 at the newly founded University of Kaiserslautern.

A more difficult decision concerned mathematics, for which many experimentalists had little regard. Initially, Einstein had shared this attitude, but then he worked hard on Riemannian geometry to understand gravity. Heisenberg’s successes were based on deep mathematics, too, but he tried his best to limit its scope. SU(2) and the analogy between spin and isospin were fundamental, and the representation theory of SU(2) had been fully explored in the context of atomic physics. Dirac’s understanding of spinors and his introduction of the delta distribution opened the way for a thorough investigation of non-compact groups like SL(2,C). This allowed us to break the wall between maths and physics, which happened initially in the Soviet Union. Rühl was very aware of this fact and was deeply impressed by the work of Israel Moiseevich Gelfand. In winter 1967/1968 he gave a series of lectures on this topic for the academic training programme at CERN, which in 1970 became the core of his book The Lorentz group and harmonic analysis. A mathematical fruit was his elementary proof of the Plancherel theorem for classical groups, published in 1969.

Rühl’s appointment to a chair at Kaiserslautern was a happy choice for both sides. Internationally recognised professors like Rühl had adequate resources for students, visitors and conferences, and four theory colleagues were hired between 1970 and 1973. In 1983–1985 Rühl was chairman of the physics department and member of the university senate. He published good papers with his PhD students and supported the global development of science, in particular through his work with postdocs from Oran University. For many years he also worked as a mentor for gifted students from all faculties for the prestigious Studienstiftung des deutschen Volkes scholarship foundation.

Despite his dominating affinity for mathematics, Rühl maintained an interest in experimental physics and occasionally published related work. His understanding of Russia facilitated successful collaborations with outstanding colleagues who had moved to the West, with some of his most important contributions stemming from his collaborations with colleagues from Yerevan. After his retirement in 2004 he continued to publish as before. Eleven years later he moved to Füssen near the Alps. For five years he could enjoy his passion for skiing, before an accident impaired his health.

Werner Rühl always had an open mind for new developments. He had studied the large-N behaviour of theories with symmetries like O(N) and did respected work on lattice theories. From the 1980s, his citation rate increased more and more – a tendency that lasted way beyond his retirement. The original take on AdS/CFT duality in the context of O(N) sigma models and high-spin theories stands out the most. At the end of his life it must have been a great satisfaction for Werner Rühl to watch the ripening of these late fruits.

Atsuhiko Ochi, a brilliant, passionate detector and experimental physicist, passed away on 29 April 2024 at the untimely age of 54. A source of innovative ideas at the forefront of radiation detectors, he made outstanding contributions to the development of micropattern gaseous detectors (MPGDs) that are recognised worldwide. He was also a distinguished lecturer whose inexhaustible passion, dedication and remarkable character captivated the many students he mentored.

Atsuhiko began his research at the Tokyo Institute of Technology, initially focusing on large-area avalanche photodiodes as fast photon and soft X-ray detectors. In 1998 he defended his PhD thesis “Study of Micro Strip Gas Chamber as a Time-Resolved X-ray Area Detector”, earning the second High Energy Physics Young Researcher’s Award from the Japan Association of High Energy Physicists. In 2000, alongside Toru Tanimori, he introduced the micro pixel chamber (micro-PIC), a new gaseous detector for X-ray, gamma-ray and charged-particle imaging. It was fully developed using printed circuit board technology and free of floating structures like wires, mesh or foils, featuring a pin-shaped anode surrounded by a ring-shaped cathode.

In 2001 Atsuhiko moved to Kobe University, where he joined the ATLAS experiment and devoted his efforts to commissioning the ATLAS thin gap chambers (TGCs). He was also in charge of integrating the front-end electronics on the KEK TGC detectors and of detector quality assurance and control. Later, at CERN, he led the acceptance quality control of the ATLAS TGCs.

Atsuhiko could always merge his love for experiments with a passion for new ideas. “We need new ‘eyes’ to catch a glimpse of science’s frontier”, he once said. Along with his group in Kobe, while making significant contributions in ATLAS to the design and construction of the new large resistive micromegas for the Muon New Small Wheel, he conducted R&D on the use of sputtered layers of diamond-like carbon (DLC) as resistive elements to quench discharges and played a crucial role in connecting with Japanese industry. He was among the first to test the technology with micromegas, apply it to the micro-PIC detector, and pioneer its use as electrodes for the novel resistive plate chambers he proposed for the MEG II experiment. He supported the use of DLC in the final TPC micromegas of the near detectors of the T2K experiment while serving as a liaison person with BE-Sput in Kyoto. DLC is now the predominant approach in most new resistive MPGD detectors.

In his research, Atsuhiko always placed great emphasis on mentoring students and giving them access to a worldwide community of experts, facilities and experiments. He meticulously shared all relevant research conducted by Japanese colleagues, ensuring proper visibility and recognition for his community. This has been crucial in the international RD51 collaboration on MPGD technologies, within which he played a significant role in its formation and management. During the transition from the MPGD-based RD51 collaboration to the upcoming DRD1, which encompasses a broader scope of technologies and applications, Atsuhiko made a crucial contribution by maintaining strong ties with the Asian community.

Atsuhiko’s vibrant enthusiasm and infectious smile leave an irreplaceable void. His departure is a profound loss, leaving behind a loving wife and two children.