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Detector Assembly Facility goes into operation

The future of the Large Hadron Collider LHC at CERN is currently being prepared at DESY. A former photon science research building has been converted into a cleanroom with a lab, and from May 2018 DESY scientists will start preparing and producing key, highly specialised components for the two huge particle detectors ATLAS and CMS at the LHC. In a few years’ time, these detectors will be joining the scientific race in search of new particles, dark matter and other unexplored phenomena. At DESY, the two research groups which will one day be rivals are working side by side in the cleanroom and the lab.

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In diesem neuen Reinraum bei DESY werden bald Detektoren für den LHC am CERN gebaut. Bild: DESY
Just a few years ago, Building 25c was still being used to conduct synchrotron radiation experiments. It has now been given a new lease of life as DESY’s Detector Assembly Facility (DAF), which will develop and build high-precision silicon detectors over the coming years. Comprehensive remodelling began in June 2016 and after a little less than two years this new facility is now being put into operation.

The next, so-called high-luminosity phase of the LHC (HL-LHC), in which the amount of data is to increase several times over, begins in 2026 and requires new, more efficient detectors for the ATLAS and CMS experiments. For each of these, DESY is building an endcap for the new silicon tracking detectors in collaboration with national and international partners. These tracking detectors are placed very close to the collision point and have to withstand and record a large number of particles. With their help, scientists can determine very precisely when and where which particles passed through the detector and so find out exactly what happened during the collision of the proton beams.  

DESY is producing and testing several thousand silicon detector modules for the high-luminosity phase and will afterwards install them in the mechanical structure of the endcaps before delivering these to CERN, where they will be connected up with the remaining detectors and put into operation.

The preliminary work and the manufacturing of the modules, with their highly sensitive silicon strip detectors, calls for extremely clean surroundings without the slightest trace of dust, because the structures on the sensor are so minute – measuring less than 100 μm, or a tenth of a millimetre – that even the tiniest grain of dust could jeopardise the quality of the product. This is why the heart of the new DAF is an ISO class 6 cleanroom, i.e. one with fewer than 35000 tiny particles per cubic metre.

In addition to the cleanroom with a floor area of 250 square metres, Building 25c contains further laboratory rooms for the preparatory work and for storing the finished modules.

After 22 months of remodelling, the cleanroom is now finished and the first pieces of equipment have been installed. These include the thin wire bonder for the CMS and the probe station for ATLAS. Further equipment is due to arrive over the coming weeks, so that in the end the ATLAS and CMS groups will be able to simultaneously begin the preliminary work for manufacturing the silicon modules in the cleanroom.

During the peak production phase a total of 3000 modules will be made for the two detectors over a period of 16 months. Up to 20 people will then be involved in different stages of the production process, from the inspection of incoming sensors at the trial stations, via the adhesive bonding of the modules’ components, and the connection of the electrical contacts with 20 μm thick wires using the thin wire bonder, through to the final inspection and calibration of the finished modules. 

However, there is not enough room in the building to carry out the final assembly of the end caps for the two experiments, each of which will be more than two metres across and boast 30 square metres of silicon detectors. For this reason, a further ISO class 7 cleanroom is currently being set up in the historic “Hall 1”, which is to be available from autumn of this year for the assembly of the end caps. In its previous life, “Hall 1” served as a research hall for DESY’s eponymous accelerator, the Deutsches Elektronen-Synchrotron.