Speaker
Prof.
Kock Kiam Gan
(Ohio State University (US))
Description
New fiber optic transceivers, opto-boards, were designed and produced to replace the first generation opto-boards installed on the ATLAS pixel detector and for the new pixel layer. Each opto-board contains one 12-channel PIN array and two 12-channel VCSEL arrays along with associated receiver/driver ASICs. The new opto-board design benefits from the first generation production and operational experience and contains several improvements. Most of the new opto-boards have been installed with completion expected in early June. We will present the design, production and operational experience, and reliability study of the new opto-boards.
Summary
The Large Hadron Collider (LHC) at CERN (Geneva) is now the highest energy and luminosity collider in the world. The collider is currently in a period of maintenance in order to increase the center-of-mass energy from 7 to 13 TeV. The pixel detector of the ATLAS experiment contains four barrel layers and three disks on each end. The inner barrel layer (insertable barrel layer, IBL) is the new addition installed during this shutdown. New opto-boards have been fabricated for the new pixel system for two reasons: 1) the IBL requires a new version of opto-boards; 2) the installation site of the opto-boards for the older pixel detector has been moved to a more accessible location.
A post-mortem has been performed on the first generation opto-boards removed from the older pixel detector. The result of the post-mortem will be presented. This result, together with the lessons learned from the production and operational experience of this first generation, have led to several improvements in the design of new opto-boards.
Each new opto-board contains one 12-channel PIN array and two 12-channel VCSEL arrays. However, only the inner eight channels of each array are used. Each PIN array couples to two four-channel receiver/decoder ASICs and each VCSEL array couples to two four-channel driver ASICs. Several improvements have been incorporated into the new design. Each optical array is now packaged in a new opto-pack with better thermal management, more reliable connections, and easier fabrication procedure. More connections have been added to reduce the chance of a single-point failure. The thermal management of the board has also been redesigned to greatly reduce the fabrication cost.
The production of the opto-boards is now completed. The production experience was quite positive although some small modifications in the design were needed at the beginning to ease the production and improve the reliability of the opto-boards. These will be presented at the Workshop.
All opto-boards have been installed except those for the IBL which will be installed in early June. The installation proceeded quite smoothly, indicating the robustness of the design. We expect to have some operational experience by the time of the Workshop, including the statistics on infant mortality, and the result will be presented.
The long-term reliability of the opto-boards has been extensively studied. The industry standard is that some sample boards must survive for at least 1,000 hours in a harsh environment, 85 C and 85% relative humidity. The study has been performed on the most critical element of an opto-board, the opto-packs, before the opto-board production, and the opto-boards from the production batch. We will present the results from the study.
Primary author
Prof.
Kock Kiam Gan
(Ohio State University (US))
