Valerio Gracco 1940–2015

Valerio Gracco, a passionate enthusiast of physics, passed away on 24 October 2015, in Geneva.

Born in Torino (Italy) on 23 December 1940, Valerio obtained his degree in physics in December 1963. His thesis was on the interaction of 14 MeV neutrons with nuclei.

Valerio spent his first years after university at LAL-Orsay (France), where he continued to study nuclear-physics interactions and photodisintegrations of deuterons from 140 to 400 MeV. He also went on to explore strong interactions and vector meson dominance (VMD) with electron–positron annihilations at the Anneau de Collisions d’Orsay (ACO).

At the end of the 1960s, Valerio became a fellow of CERN. At the CERN PS, he participated in the S91 experiment under the guidance of Arne Lundby. The experiment studied the elastic scattering of protons, pions and kaons on 5 GeV and 10 GeV/c protons, and was then extended under the name S120 to also encompass studies on a few inelastic channels (two-body production of a hypercharge state).

In 1976, while he was a research associate in the INFN group of Sergio Ferroni in Genova (Italy), Valerio and Lundby proposed the WA7 experiment, which used large proportional chambers (3 × 3 m2) built at the Ponte Carrega Laboratory (Genova). WA7 ran in CERN’s West Area and used a beam of 20 and 30 GeV to study pion and proton large-angle elastic scattering on protons.

In 1978, he was appointed a full professor and, in the same year, he also became director of the INFN Section in Genova. In 1980, Valerio started a two-year mandate as a member of the INFN Executive Board ("Giunta") and vice-president of the INFN Council. These years were marked by the hard R&D work and important progress made on the development of instrumentation for experiments at CERN. This success was made possible by Valerio’s collaboration with excellent technicians, but it was also due to his dedication in teaching experimental laboratory classes and detector techniques with a modern outlook and spirit.

In 1980, Valerio joined the group at CERN who proposed to study charmonium spectroscopy by using antiproton annihilations on protons from a hydrogen-gas jet target. That target demanded an important technological development that was mainly provided by the Genova INFN and GNSM teams that worked closely with the ISR staff.

By 1983, the jet target was installed in one of the ISR rings and the experiment R704 could take data until the closure of the ISR machine in June 1984.

After 1982, Valerio started to moderate his heavy involvement with the INFN organisation and management, and went on to think of the best way to involve the Genova team with the LEP experiments. He initially joined the OPAL collaboration, but then decided to move to COLLEPS (later called DELPHI) led by Ugo Amaldi. He suggested that Ansaldo (an industry based in Genova) build the superconducting solenoid for the experiment, and even obtained the necessary funds. However, the collaboration decided to build it with other partners. Valerio stayed in the collaboration and participated in work for the technical proposal published in 1983. DELPHI was built between 1983 and 1988, and operated up to the end of 2000. The Genova team built nearly half of the DELPHI electromagnetic calorimeter (HPC), and a large number of physicists collaborated in the hardware and software development, and data analysis. Within the collaboration, Valerio had several prestigious roles, including physics co-ordinator and project leader of the RICH group and of the HPC.

In the second half of the 1990s, while continuing to be involved in high-energy particle-physics projects, his interests also turned to cosmic-radiation physics, with the aim of consolidating participation of the Genova team in this field of physics. He led the participation of the group in the AirWatch/EUSO enterprise to build an Earth-orbiting observatory watching from space the extensive air showers produced by cosmic radiation in the atmosphere. He contributed personally to the important role of the group in the project design.

In parallel, approaching the LHC era, he also led the participation of the Genova team in LHCb, where the group contributed substantially to the mechanics, electronics and controls of the RICH detectors.

Valerio also devoted a lot of his time to teaching, ranging from experimental laboratory physics to general physics and astroparticle physics. He was an excellent and demanding teacher, while also keeping himself up-to-date.

His knowledge of and enthusiasm for physics was huge. He was a hard worker, always available whenever needed, either to be on call or participating in a test beam. He was demanding to his collaborators, but no more than he was with himself.

We remember the past, the work he accomplished, and the many physics achievements of Valerio Gracco. All of this remains, and gives strength to our community and, we hope, to his wife, Maja. To her, we express our warmest sympathy.

• His friends and colleagues.

Berend Kuiper 1930–2016

Berend Kuiper arrived at CERN at the beginning of 1956, having graduated as an engineer from the prestigious Technical University of Delft in the Netherlands.

At the time, the team led by John Adams and tasked with the construction of the PS was still housed in the barracks next to the Physics Institute of the University of Geneva, only later moving to Meyrin.

Berend was assigned to the Magnet Group, directed by Colin Ramm, and here he joined colleagues Bas de Raad, Renzo Resegotti, Simon van der Meer and, a few months later, Günther Plass.

The project was destined to build the first synchrotron using the alternating-gradient principle. One of its challenges was to produce a magnetic field that was extremely uniform over the entire 628 m circumference of the PS.

It was therefore the principal task of the group to produce a series of 100 magnets with extreme precision. Berend and his colleagues proceeded to make magnetic measurements.

Today, almost 60 years later, the same magnets are still being used to produce the protons that feed the LHC.

A few years later, with his colleague Günther Plass, Berend constructed the first fast-extraction system for the PS beam.

That was the prelude for construction of the fast-ejection system for the Soviet synchrotron at Serpukhov near Moscow, which at the time was the most powerful machine in the world.

Berend, heading a team of some 40 engineers and technicians from CERN, some accompanied by family members, left for nearly six months in Russia to install this extraction system designed and built at CERN. Taking into account the context of the period, it was a rather exceptional enterprise, because all of the components and tools had to be shipped – from the tiniest screw to the smallest screwdriver.

The complex, including a beam-transport system and a radiofrequency separator, was CERN’s contribution that allowed European physicists to use a machine that did not have an equivalent in the scientific world.

Back at CERN, Berend was one of a handful of staff who contributed to the start of a new European scientific organisation – ESO.

He participated in the project for the first big telescope to be installed in Chile.

At the start of the 1970s, he was put in charge of renovating the PS control system, which had evolved into a heterogeneous assembly of disparate elements (linear accelerators, injectors, main ring, etc) but needed to become the injector for the SPS to-be.

Berend was a polyvalent engineer, and although a priori he was not a specialist in these techniques, he built a coherent system with great adaptive potential. The system was capable of integrating the needs of the SPS, followed by the production and accumulation of antiprotons, then LEP and finally the LHC.

In 1985, he launched the International Conference on Accelerator and Large Experimental Physics Control Systems (ICALEPCS), to bring together all high-energy physics labs for discussions on controls.

These conferences have become the touchstone in the area of controls, and Berend was the guest of honour at the 10th conference, held in Geneva in 2005 (the 15th took place in Melbourne in 2015).

With his big lanky silhouette and unshakable optimism, Berend leaves us with the memory of a great engineer, rigorous but always inspiring his collaborators in the face of external constraints, and able to reach set goals under difficult circumstances.

It is with people like him that CERN achieved the scientific successes that put Europe at the forefront of world science.

• His friends and colleagues.

David C Rahm 1927–2016

Dave Rahm was an experimental physicist who spent almost his entire career at Brookhaven National Laboratory (BNL), and a significant part of his research was carried out at CERN. He passed away on 20 March.

Dave was fortunate to work with many great scientists. In 1956, he worked on the first bubble chambers for his PhD with Donald Glaser at the University of Michigan. Glaser won the 1960 Nobel Prize in Physics for their work. Dave started working at BNL in 1954. He took leave from BNL in 1960–1961 to work at Saclay in France on bubble chambers with Bernard Gregory, who later became Director-General at CERN. Dave continued contributing to bubble chambers at BNL, for example on the experiment that used the 80" chamber to discovery the Ω. He was a visiting scientist at CERN in 1968 and 1969, and worked with Nobel laureate Georges Charpak and Herb Steiner during the development of multiwire proportional chambers (MPCs).

In the mid-1970s, Dave started working as a member of the Omega Group with Bill Willis and Veljko Radeka on a liquid-argon (LAr) electromagnetic (EM) calorimeter and a lithium-foil radiator (TRD) Xe-proportional wire-chamber transition radiation detector for ISR experiments 806, 807 and 808. Dave also worked with Bob Palmer on superconducting magnets for Isabelle.

In the 1990s, he worked on the RD3 accordion EM LAr calorimeter with Daniel Fournier of Orsay. Dave also worked on the calorimeters of the NA34 and NA44 experiments. In the same years, he also took part in the GEM experiment at the SSC, and carried out a beam test of a liquid-krypton EM calorimeter at CERN. From 1994 until his retirement in 2001, he worked on the ATLAS LAr calorimeters and cathode strip muon chambers.

Dave was an expert in many aspects of detectors, and was very gregarious. We all very much miss the opportunity to consult with him on many subjects.

• His colleagues at BNL.

Bruno Zotter 1932–2015

Bruno Zotter passed away on 22 December 2015. He was one of the leading theoretical accelerator physicists who made essential contributions in the recent period of development of particle accelerators after single-particle stability became well understood, and after which the interaction of beams of increasing intensity with themselves and their environment moved into focus.

Bruno was the right man at the right time for this. His thesis at the Technische Hochschule in Vienna dealt with the calculation of electromagnetic fields in high-frequency cavities, one of the topics that accompanied him for the rest of his professional career, which after a short stint at the International Patent Office in The Hague, started with work on low-noise travelling-wave tubes in a US government laboratory in New Jersey.

The predictable decline of this line of research due to the emergence of semiconductor applications led him to move into the related particle-accelerator field at CERN’s ISR, where the importance of high-intensity beam phenomena had already been realised during the construction phase.

Bruno refined existing models and developed new ones, favouring an analytical approach in his many contributions that laid the foundations for the steady increase in circulating proton-beam current up to 40 A, typically.

He had a propensity for theory and mathematics. A sign of this is his work on the summation of infinite algebraic and Fourier series, but he also participated in experimental work in parallel to advancing theoretical understanding. This included topics as diverse as space-charge phenomena, beam–beam effects, and definition and determination of the accelerator coupling impedance characterising the potential of the adverse interaction of a vacuum chamber with the beam, depending on the frequency spectrum of the latter. He also applied his insight when the Super Proton Synchrotron became affected by high-intensity effects after the running-in phase, and he actively participated in CERN’s studies of the options for a post-ISR accelerator at the high-energy frontier, the most prominent examples being LEP, the LHC and CLIC.

LEP offered an ideal playground for Bruno, in particular, the interaction of the very short, intense electron bunches with the vacuum enclosure and the long array of RF cavities. An impressive set of publications illustrates his tenacious investment, where he put the enormous increase in computer power to good use to refine the comprehensive simulations of collective effects. Although an appreciated lecturer at accelerator schools and workshops, he also found time to summarise the main part of his work in the book Impedances and Wakes in High-Energy Accelerators, written with his friend Sam Kheifets from SLAC.

His competence, steady focus on high-level electrodynamics-related accelerator physics, and an extraordinary gift for tutoring, attracted an amazing number of students and visitors to work with him. Many visitors from abroad remember with gratitude his generous help in overcoming bureaucratic hurdles and getting around in the Geneva area. His colleagues remember him as an open but independently minded, often sarcastic, discussion partner. He was known for perseveringly pondering over problems seemingly too difficult or tedious for the rest of us, but tricky and, therefore, interesting enough to be worth his investment. After some gestation, he would discreetly put his solution on the table. He stayed active in the field, even after his retirement in 1997, remaining a valued tutor, discussion partner and co-author, with a vivid interest in the latest developments and measurement results obtained in the CERN accelerators continuously being pushed for higher performance.

Having enjoyed over the years his competence and his benevolent, unassuming attitude, we are proud to have had the chance to work with him, be it as colleague, visitor or student.

• His friends and colleagues.