Speaker
Description
Summary
The CMS Tracker Collaboration forsees an upgrade of its pixel detector in the shutdown 2016/2017. Improvements include one additional layer and disk, respectively, less material, a CO2 cooling system, and reduced deadtime at large hit rates, due to a new readout chip. The new detector will comprise a factor of 1.9 more channels, and consequently the power consumption will increase by almost a factor of two. Since this power has to be supplied with the installed cable plant, a novel powering scheme is mandatory. A powering scheme based on the DC-DC conversion technique has been chosen.
We develop DC-DC buck converters, based on the AMISx chip family by CERN, specifically for the application in the CMS pixel detector. The current DC-DC converters, based on the AMIS4 full size prototype ASIC, will be introduced and their performance will be presented. Their integration into the CMS pixel detector will be described. The focus of our studies is on system aspects. System tests with up to eight AMIS4 converters and two CMS pixel modules have been performed, and show no degradation of the module noise performance. DC-DC converters feature an efficiency of the order of 80% and thus dissipate considerable heat. Cooling of the DC-DC converters is therefore mandatory and has been studied both with standalone measurements and with a prototype CO2 cooling system. A dedicated service board for 24 DC-DC converters has been developed and first performance tests with a fully equipped board will be presented. Further studies include thermal cycling of converters down to the future operating temperature, and an investigation of potential frequency locking of several DC-DC converters.
