Abstract
During the high-luminosity phase of the LHC (HL-LHC), planned to start in 2027, the accelerator is expected to deliver an instantaneous peak luminosity of up to 7.5×1034 cm−2 s−1. A total integrated luminosity of 0300 or even 0400 fb−1 is foreseen to be delivered to the general purpose detectors ATLAS and CMS over a decade, thereby increasing the discovery potential of the LHC experiments significantly. The CMS detector will undergo a major upgrade for the HL-LHC, with entirely new tracking detectors consisting of an Outer Tracker and Inner Tracker. However, the new tracking system will be exposed to a significantly higher radiation than the current tracker, requiring new radiation-hard sensors. CMS initiated an extensive irradiation and measurement campaign starting in 2009 to systematically compare the properties of different silicon materials and design choices for the Outer Tracker sensors. Several test structures and sensors were designed and implemented on 18 different combinations of wafer materials, thicknesses, and production technologies. The devices were electrically characterized before and after irradiation with neutrons, and with protons of different energies, with fluences corresponding to those expected at different radii of the CMS Outer Tracker after 0300 fb−1. The tests performed include studies with β sources, lasers, and beam scans. This paper compares the performance of different options for the HL-LHC silicon sensors with a focus on silicon bulk material and thickness.
Highlights
In this paper we have presented results of measurements of pad diodes and strip sensors
They require operation voltages of up to 800 V at the end of the HL-LHC running period
Summary
The design concept for the new CMS tracker [6] is based on requirements to maintain efficient tracking capabilities under high-luminosity conditions. CMS tracking system is extended significantly up to a pseudorapidity of |η| = 4.0, mainly by adding forward pixel stations. Hits on the two sensors, which are separated by 1.6 to 4 mm depending on the position of the module, are correlated in the front-end chip This allows the discrimination of high- from low-pT tracks based on their curvature in the 3.8 T magnetic field of the CMS solenoid. The new tracker will use two-phase CO2 cooling to remove the heat generated by the sensors and the electronics This choice makes it possible to operate and maintain the sensors at −20 ◦C or less, reducing the power consumption due to the leakage current of the sensors and effectively preventing an increase in the full depletion voltage, Vfd, due to reverse annealing. Power losses on the low voltage cables will be reduced by using on-module DC-DC converters
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