Speaker
Description
The AdvancedTCA (ATCA) telecom industry standard has been selected as the hardware platform for the “Phase-II Upgrade” of ATLAS at the Large Hadron Collider (LHC) at CERN.
In November 2014 a project dedicated to the study of the impact of the ATCA integration in the actual counting rooms was launched analyzing the impact on the cooling infrastructures. A spare rack equipped with two ATCA shelves, high power dissipating load blades, temperature and air velocity sensors were installed in a lab. Vertical and horizontal cooling performance were checked and some critical aspects identified.
The test results will be presented.
Summary
The AdvancedTCA (ATCA) telecom industry standard has been selected as the hardware platform for the “Phase-II Upgrade” of the back-end electronics systems of the ATLAS experiment at the Large Hadron Collider (LHC) at CERN. This hardware is going to replace part of the actual electronic equipment, mostly based on VME, and less demanding in terms of cooling performances.
For historical reasons at ATLAS experiment the electronics equipment in the so-called LHC racks are cooled by a closed vertical recirculating airflow system from bottom to top. All such racks are equipped with a main ventilation unit housing a smoke detection system on top of other ambient temperature sensors. This existing airflow system is not compatible with the default telecom industry ATCA standard based on horizontal airflow. Additionally, ATCA boards will dissipate a significantly larger power with respect to the actual equipment and the cooling performance of the existing rack infrastructure could become an issue.
During 2014, the Electronics Systems for Experiments (PH-ESE) group at CERN, has launched an evaluation project that mainly focuses on the electronics infrastructure itself towards the proposal of common specifications across the LHC experiments. However, the integration of these new shelf types in the existing rack infrastructure of the ATLAS experiment must be assessed separately especially the impact on the room cooling and noise. For this reason, the ATLAS technical coordination launched in November 2014 a project dedicated to the study of the cooling infrastructure capabilities for the upgrades.
An ATCA shelve can house up to 14 blades, the target max power dissipation foreseen is 450W/blades. Thus the total power dissipated by one shelve, including the required internal fan power, can exceed 7 kW. For the cooling integration study, a spare rack was equipped with about 200 temperature sensors, two ATCA shelves equipped with 28 load blades in total, 14 of them were limited to a maximum power dissipation of 350W/blade while the others could dissipate up to 600W/blade: the average power dissipation of 450W/blade could be checked properly.
Different shelf layouts (vertical and horizontal airflow), power loads, number of heat exchangers, fans configurations, failure modes and low water temperature configurations were tested and compared with simulations carried out by an ATCA shelf manufacturer. Many conditions were tested in order to assess the impact on the counting room environment (i.e.: air conditioning,, noise, etc.).
The very high noise level of these shelves was another important aspect to be studied; some preliminary tests on the integration of sound proofing panels in the rack were carried out too.
The project aimed also to provide guidelines to the electronic developer regarding the cooling limits of the racks in terms of horizontal and vertical airflow distribution homogeneity through the boards. The recommendations resulting from this study will be relevant also for the other LHC experiments that will based on ATCA their electronics systems upgrades.
The results of the whole rack cooling and integration test campaign, the cooling performances and improvements as well as the resulting conclusions will be presented.
