Hardware prototyping and thermal simulations of strip sensor, and simulation of transmission lines for the LHCb VELO upgrade

Longstaff, Iain (2022) Hardware prototyping and thermal simulations of strip sensor, and simulation of transmission lines for the LHCb VELO upgrade. MSc(R) thesis, University of Glasgow.

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Abstract

The LHCb experiment based at CERN’s Large Hadron Collider (LHC) particle accelerator is undergoing upgrades to replace end of life detectors and take advantage of the luminosity upgrades that the LHC machine is gaining.
The VErtex LOcator (VELO) is a particle tracking sub detector of LHCb and its upgrade is designed to record up to an order of magnitude more data from proton-proton collision events. During the development of the upgrade, silicon strip sensors and pixel detectors were investigated as options.
A prototype of the strip sensor was assembled with readout hardware to characterise its performance. Cooling methods were considered and thermal simulations were performed to verify that cooling an irradiated silicon strip sensors after 50 fb−1 of integrated luminosity is viable. Using the technologically least aggressive and hence easier to implement cooling solution required liquid CO2 to be below -18◦C to avoid thermal runaway, the upgraded CO2 cooling infrastructure is capable of -30◦C hence thermal control is viable.
The silicon pixel sensor technology was chosen for its superior track reconstruction performance as the upgrade technology. It requires around 2.85 Tbits/s of data to be transferred for processing off-site. The sensor’s readout electronics require multiple parallel transmission lines capable of each carrying 5.12 Gbits/s of data without significant signal loss and also have sufficient flexibility to accommodate the 3 cm lateral movement of the VELO sub detector halves.
A flexible copper multilayer ribbon cable design, so called “flex cables”, is a compact solution, with a thickness just over 400 µm where each transmission line is 1200 µm wide. Simulations were performed to find the optimal characteristic differential impedance and transmission properties which were used to guide the prototype development. Comparisons of impedance measurements against real world prototype versions showed a systematic bias of around 10 Ω that could be explained by various factors explored within. Comparisons of transmission versus frequency showed good agreement between simulation and measurement. The flex-cable design has been finalised and the VELO upgrade is being assembled in preparation for on site installation into the LHCb detector.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
Supervisor's Name: Eklund, Professor Lars and Soler, Professor Paul
Date of Award: 2022
Depositing User: Theses Team
Unique ID: glathesis:2022-82756
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 May 2022 08:27
Last Modified: 11 May 2022 08:27
Thesis DOI: 10.5525/gla.thesis.82756
URI: https://theses.gla.ac.uk/id/eprint/82756

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