CERN Accelerating science

The PH Detector Technology (PH DT) group


PHDT is one of the three technical support groups in the physics department. Our main mandate is to develop, construct, operate and maintain detectors components for physics experiments at CERN. Our competencies span over a very wide spectrum from classical mechanics and composite materials over thin films and gas systems to solid state, gas and photodetectors. During the past decade we were involved in numerous LHC projects and worked together with the 5 collaborations (ALICE, ATLAS, CMS, LHCb and TOTEM) on the design and construction of 12 detectors. In recent years, new nonLHC activities like NA62, AEgIS, CAST, CLOUD were added and the first steps towards the LHC upgrade were taken. We also run a number of services, available to all CERN users, in order to centralize support and, where appropriate, to standardize equipment and approach. R&D in a few strategic fields with clear relevance for future applications at LHC or other CERN experiments round up our spectrum.

Technical support groups have a long tradition at CERN. Our strength lies in developing infrastructure and equipment and accumulating expertise and know‐how in certain domains, which we can then apply to several projects. We work in close collaboration with the experiment teams and discuss with them about new projects, resource schedules and deliverables.

DT was formed in May 2008 in a fusion of the DT1 and DT2 groups, which had been formed in 2005 by merging the three technical assistance groups (TA1–3). The latter ones had existed since the early 1990s.

Today, the DT group comprises about 80 staff, of which approximately one half are (electro‐) mechanical technicians and designers and the other half physicists and engineers. The majority of the 20 fellows and students in DT work on the various R&D activities described below. For historical reasons the personnel, workshops and labs are spread over many buildings – a situation which we hope to improve in the future. The 5 sections of the group represent the administrative structure, however we use a matrix organization to form teams for the various projects.


For us, 2009 and 2010 are transition years. The major LHC detector projects are completed and we participate in their operation and maintenance, however major activities, which are being discussed in view of a LHC luminosity upgrade, have obviously not yet started. Two LHC detector construction activities are still in full swing: ATLAS ALFA, a scintillating fibre based tracking detector system for absolute luminosity measurement, which is foreseen to be installed later this year in so‐called Roman Pots at z = ±240 m from the IP1, and TOTEM RP, a silicon based tracking detector for total cross‐section measurement at IP5, also mounted in Roman Pots. Half of the TOTEM detector hardware (12 detectors) is installed and commissioned; the other 12 will follow later this year. The definition of LH consolidation and upgrade projects is ongoing (e.g. ATLAS IBL, ATLAS tracker upgrade, ALICE VHMPID and DCal) and technical work has actually started.

This temporary drop in LHC activities gave us the opportunity to support several new non‐LHC activities, namely NA62, CLOUD and AEgIS. For all three, DT members ensure the coordination of the technical activities. In NA62, the rare kaon decay experiment in the North Area, we committed to the development of a high resolution and low mass straw tracker to be operated in the decay volume (vacuum) and to the huge radiator vessel of the RICH detector. For CLOUD (see January issue of the PH Newsletter) we built the complex gas, thermal and HV systems and support all technical activities. For AEgIS, the new anti‐hydrogen gravitation experiment in the AD complex, one of our contributions is the construction of a coil winding machine, which we will use to construct relatively small but precise superconducting solenoid coils.

Hans Danielsson (on the right) with his team behind the recently completed NA62 64 straws prototype detector.

AEgIS project: Francois Garnier (on the left) and Pierre-Ange Guidici test winding machine by winding a test coil with a superconducting wire.



Workshop and services 

Our mechanical workshops and services are the technical backbone of the group. We run three major mechanical workshops with different focus (essentially the former TA1‐3 workshops) and a number of specialized workshops (e.g. scintillators, gluing techniques, glass and ceramics). In all workshops, we often host visiting technicians from the collaborations, one workshop (B108) also serves as support for the ATLAS activities at point 1. In the past few years we have been able to modernize the machine park by the acquisition of a computer numerical controlled (CNC) 3‐axes milling machine and a CNC 4‐axes lathe which allows us to cope with requests for complex and high precision components, used e.g. for tracking detectors. For component verification and in‐situ alignment, fast metrological feedback is indispensable. 


This is why we invested in various tools like portable, tactile and optical coordinate measurement machines.

A substantial fraction of our activities are concentrated in the various technical services that we try to tailor to the changing needs of the users. We consider this an efficient way of providing support to a large community. It automatically leads to sharing of resources and enforces a certain degree of standardization. Our services comprise

•Gas Systems Service (built and operates all LHC gas systems, incl. 24h piquet),
•Proton/neutron irradiation facility (PS T7, ~1500 irradiated samples per year) and GIF (B180),
•Controls (LHC experiment magnet, vacuum, rack and motor control, incl. 24h piquet),
•Thin film and glass service (functional coatings, photocathodes, glass and ceramic machining)
•Departmental silicon facility (DSF) and bond lab
•Magnetic field measurements.

Radiation qualification was a key issue for the LHC detectors and will be even more important for upgrade projects where fluences of up to 1016 cm-2, (1 MeV n equivalent) are expected. Increasing the performance of both the p/n and gamma facilities is therefore high up on our priority list.

Antoine Giupet, technician in the bond lab,works on a CMS tracker hybrid

Philippe Lancon and André Braem verify a wire positioning tool with the tactile Coordinate Measurement Machine CMM).


Jerome Bendotti programs the 4axes CNC lathe with driven tools. The high precision machine allows for combined urning and milling operations. 


R&D 11

Traditionally, there are three areas where DT and its predecessor groups were performing detector R&D: Micro Pattern Gas Detectors (mainly GEM based), radiation hard silicon detectors and hybrid photodetectors. Given their high relevance for LHC and possible upgrades, the first two activities were significantly increased in the past few years, funded mainly through the so‐called White Paper funds (WP4 and WP5) and supported by fellows from the FP7 Marie Curie training network MC‐PAD. While WP4 focuses on radiation hard materials and structures for the inner most silicon tracking detectors, WP5 aims to develop the technology for large area gas based detectors which could e.g. provide superior performance for muon detection at LHC. We initiated the formation of the international R&D collaborations RD50 and later also RD51 in order to bundle and focus the numerous but uncoordinated activities in the world wide community. The increasingly interweaved activities between these RD collaborations and the experiment teams seem to indicate that the approach was successful.

Several other domains were identified as crucial for the consolidation and upgrade of the LHC detectors. One is detector cooling, particularly critical for the inner tracking detectors, where the available space, accessibility, radiation levels and the material budget pose complex constraints to the evacuation of the ever increasing dissipated power. Others are quality assurance and reliability testing, but also material and gas aging studies, and last but not least, advanced 3D models of as‐built structures, pipes and cables, e.g. for the preparation of repair and replacement interventions, particularly in activated environments. Our efforts in these domains aim to tackle the most urgent problems and provide the basis for an adequate service in the years to come.


Point cloud image for CAD reconstruction of the Atlas Inner Detector services (on the cryostat flange). The image was obtained using a Faro 3D laser scanner at 125000 points/s from 12 positions in the cavern.