It was with great sadness that we learned that Ferdi Hahn passed away on 4 March. He was an enthusiastic and highly skilled colleague, and an openhearted friend.
Ferdi first came to CERN in 1987 as technical student of the University of Wuppertal, when he joined the barrel-RICH project for the DELPHI experiment at LEP. As part of his diploma thesis, he participated in the photon detector project, SYBIL, a TPC-like drift chamber with single photoelectron detection, which was a prototype of the DELPHI barrel-RICH system.
Here, Ferdi became very much acquainted with all hardware and software aspects of such a test program, 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. A specific part of the detector was not delivered in time, so Ferdi immediately drove 800 km to the company and back again to allow the start of data taking on time in 1989. Later, Ferdi completed his PhD with a measurement of the differential cross-sections of charged kaons and protons using the DELPHI detector, taking advantage of the unique RICH system.
In 1995 Ferdi joined the CERN physics department as a member of the DELPHI gas group. As section leader in the support groups to CERN experiments and deputy group leader of the DELPHI detector unit, he perfected the operation of the many and complex DELPHI gas systems. He also structured the LHC experiments gas working-group, which led to a professional and efficient system for all LHC detectors.
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 with considerable commitment and great competence in many experimental aspects. Through the preparation of the Technical Design Report and the coordination of the entire installation of the experiment, his exquisite ability to bring 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 agreed to support the physics department as deputy head 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 manner, patience and 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 smile made it easy to discuss subjects, even when they 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.
