Summary 500 words
For the upgrade of the CMS pixel detector it is foreseen to install DC-DC buck converters, based on radiation-tolerant ASICs from the CERN electronics group, on the so-called supply tube of the detector, approximately 2m away from the pixel sensors.
The implementation of DC-DC buck converters into CMS raises several challenges. Switching in the MHz range might inject conducted noise into the detector system while air-core inductors, needed due to the saturation of ferrite cores in the 3.8 T magnetic field of CMS, might radiate electromagnetic noise. In addition, buck converters can act as negative impedances, thereby implicating the risk of destabilizing the power supply chain. All of these potential problems have to be eliminated or excluded on system level before the new powering scheme can be installed.
To comply with the limited space available, a compact and low-mass scheme of implementation has been developed at Aachen. Based on this scheme a set-up, very similar to the intended detector system, was build, allowing system test measurements under realistic conditions. This set-up consists of the original power supply chain of the present pixel detector, a pixel sensor module, a mock-up structure of the supply tube and radiation tolerant buck converters. The effect of DC-DC buck converters on a pixel module was studied at room and cold temperatures. The influence of the expected load alternations was measured and different sensing scenarios were tested with the goal to provide a robust power plant that is compatible with the time schedule. This talk summarizes the results.