High resolution tracking with scintillating fibres - The LHCb SciFi Tracker
by Dr. Lukas Gruber (CERN)
at SMI - Boltzmanngasse 3, 1090 Wien ( 3-2-08 - Seminarraum )
Dr. Lukas Gruber
The use of plastic scintillating fibres (SciFi) as active elements in particle detectors has a long tradition. In recent years, the development of high performance SiPM detector arrays revived the interest in the SciFi technology. Combining the two technologies allows to build intrinsically fast, low mass high resolution tracking detectors with great geometrical flexibility. As a recent example, the LHCb SciFi tracker is going to replace the current outer and inner trackers, consisting of straw tubes and silicon micro strip detectors, respectively, by using a single detector technology – 11,000 km of scintillating fibres with 250 µm diameter, enabling a spatial resolution of better than 100 µm for charged particles.
The LHCb tracker requirements and environment push both the SciFi and SiPM technology to the limits. During operation the SiPMs will be exposed to a total neutron fluence of up to 6 × 1011 neq/cm2 and have to be cooled to -40 ºC to reduce the dark count rate and retain single photon counting capability. The fibres are required to have long attenuation length, high light yield and should be radiation tolerant, since close to the beam pipe an ionizing dose of 35 kGy is expected. The trigger-less readout of 524k SiPM channels at a rate of 40 MHz and the complex detector integration pose other major challenges.
The seminar talk will give an introduction about scintillating fibres and their usage for particle tracking, including a brief history of SciFi trackers. As a recent example, the LHCb SciFi tracker will be discussed in detail to give an insight into the detector design, the challenges and requirements and the status of the production process and performance of the various detector components. Furthermore, a short outlook to future upgrades will be given. In this context, I will also report on the most recent achievements of an R&D initiative aiming at the development of very fast and efficient scintillating fibres, which are based on a novel type of luminophores (NOL).