Inner tracker future planning
Barbara Warmbein, 24/07/2017

When the luminosity in the LHC goes up, the detectors need to be prepared. Detector developers are flocking to test facilities to check the quality of their new sensors, the interplay between data taking, data acquisition software and analysis tools. A particularly international team recently tested a prototype detector for the planned ATLAS inner tracker upgrade in an AIDA beamline at the German lab DESY.

“We are taking our prototype to the test beam several times to test it under as many configurations as possible,” explains coordinator Andrew Blue from the University of Glasgow in the UK.

“Every time we have a new prototype, every time a prototype has been irradiated to imitate years of data taking, we need to check its functionality, ideally with beam.”

Their particular prototype, a silicon strip detector, is on a European tour of AIDA facilities, having passed through Freiburg, to DESY and later to CERN. Thanks to transnational access funds the shift crew consisted of some 20 shifters from 13 institutes including scientists from Canada, China and South Africa. The inner tracker project consists of over 300 people from 21 countries.

The strip detector is one of two newly developed systems for a new inner tracker for the ATLAS experiment that will replace the current one in preparation for the high-luminosity LHC scheduled to go live in around 2025. The increased luminosity will put detectors under even greater stress: higher particle densities lead to higher occupancy, and increased radiation levels mean detectors must be more resilient to radiation exposure than before.  The innermost part of the new inner tracker (or ITk) based completely on silicon detector technology will consist of a pixel detector, the outer layers will be formed by the strip detector.

The brand new strip prototype is being tested with the help of the AIDA test beam telescope.  The 10x9-centimetre endcap module was assembled at Freiburg University in Germany and is the same design (without the final read out AISCs) as the estimated 7000 modules needed for the endcap system in the final inner tracker.

“The questions we ask are: is its resolution okay? What’s the signal-to-noise ratio? Does the cooling work, how is the readout system performing? ” says Blue.

“The tricky thing is: the strip detectors on the endcaps are arranged in a radial way, and nobody has tested radial strips before with the testbeam analysis software.”

The results are making sense so far, he adds. After this initial test beam on the new prototype it will undergo irradiation at CERN and will be tested again for further analysis.

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