It was with great sadness that we learned that Ferdi Hahn had passed away on 4 March 2018: an enthusiastic and highly skilled colleague, and an openhearted friend.

Ferdi first came to CERN in 1987 as a technical student from the University of Wuppertal, when he joined the EF division and the DELPHI Barrel RICH project. As part of his diploma thesis, he participated in the photon detector project, SYBIL, a TPC-like drift chamber with single photoelectron detection: a prototype of the DELPHI Barrel RICH system. SYBIL consisted of a test setup, in which single electrons were produced by a laser inside a gas volume of a drift tube and detected by a multiwire proportional chamber with anode and cathode readout. Here, Ferdi became very much acquainted with all hard- and software aspects of such a test programme, both in the innumerable technical matters and in the analysis of the data taken. From 1990, as a CERN fellow he was heavily involved in the commissioning of the drift tubes of the RICH detector, a particularity of the DELPHI experiment, followed by the development of the temperature control of the Barrel RICH. Later, Ferdi completed his PhD with the measurement of the differential cross-sections of charged kaons and protons at LEP with the DELPHI detector, taking advantage of the unique RICH system.

In 1995, Ferdi joined the Particle Physics Experiments Division as a member of the Gas group in DELPHI. As section leader in TA1 and deputy group leader of the DELPHI detector unit, he perfected the operation of the many and complex DELPHI gas systems, while at the same time he structured the LHC gas working-group, an essential step towards a very professional and efficient development of common gas systems for all the LHC experiments.  

After having led the Detector Technology group of the Physics department between 2007 and 2008, Ferdi then took over the technical coordination of the NA62 experiment. Without his considerable commitment and his great competence with the many experimental aspects, this experiment would probably never have reached its current excellent state. Through the preparation of the Technical Design Report and the coordination of the entire installation of the experiment, his exquisite capability of bringing collaborators from all kinds of cultures together was clearly an asset for the success of the project.

Knowing that the NA62 experiment was operating smoothly, Ferdi happily accepted to support the Physics Department Head as deputy in 2015. As part of the management, he was in charge of the coordination of the technical groups in the department, including the planning of personnel. With his pleasant patience and his exemplary communication skills, he solved numerous tricky problems.

Ferdi was treasured as a close colleague by many; it was a pleasure to work with him. His open character and ready smile made it easy to discuss things together, even when the discussion involved complicated issues. He was enthusiastic and full of energy, always ready to help. His friendly way of dealing with people was backed up by a deep competence in technical issues. He was one of a kind, and will be sadly missed.

Our deepest sympathy goes to his wife, son and family.

His colleagues and friends