J. Sammet

Experimental Studies Towards a DC-DC Conversion Powering Scheme for the CMS Silicon Strip Tracker at SLHC

The upgrade of the CMS silicon tracker for the Super-LHC presents many challenges. The distribution of power to the tracker is considered particularly difficult, as the tracker power consumption is expected to be similar to or higher than today, while the operating voltage will decrease and power cables cannot be exchanged or added. The CMS tracker has adopted parallel powering with DC-DC conversion as the baseline solution to the powering problem. In this paper, experimental studies of such a DC-DC conversion powering scheme are presented, including system test measurements with custom DC-DC converters and current strip tracker structures, studies of the detector susceptibility to conductive noise, and simulations of the effect of novel powering schemes on the strip tracker material budget.

DC-DC buck converters for the CMS Tracker upgrade at SLHC

The CMS experiment at the Large Hadron Collider (LHC) at CERN, Geneva, is planning major upgrades of its current pixel and strip detectors for the LHC luminosity upgrade, known as the SLHC. Due to the larger channel count and — in case of the strip tracker — increased functionality, the powering scheme adopted today, namely parallel powering of several detector modules, has to be abandoned. Instead, a powering scheme based on the DC-DC conversion technique is foreseen, which would lead to lower power losses in the supply cables, and would allow to reduce the material budget of cables and associated electronic boards in the sensitive detector volume. This paper deals with the development, characterisation and optimisation of DC-DC buck converter prototypes for the upgrades of the CMS pixel and strip detectors at the SLHC.

System Tests with DC-DC Converters for the CMS Silicon Strip Tracker at SLHC

The delivery of power is considered to be one of the major challenges for the upgrade of the CMS silicon strip tracker for SLHC. The inevitable increase in granularity and complexity of the device is expected to result in a power consumption comparable or even higher than the power consumption of todays’ strip tracker. However, the space available for cables will remain the same. In addition, a further increase of the tracker material budget due to cables and cooling is considered inacceptable, as the performance of the CMS detector must not be compromised for the upgrade. Novel powering schemes such as serial powering or usage of DC-DC converters have been proposed to solve the problem. To test the second option, substructures of the current CMS silicon strip tracker have been operated for the first time with off-the-shelf DC-DC buck converters as well as with first prototypes of custom-designed DC-DC converters. The tests are described and the results are discussed.

Development of a DC-DC conversion powering scheme for the CMS Phase-1 pixel upgrade

A novel powering scheme based on the DC-DC conversion technique will be exploited to power the CMS Phase-1 pixel detector. DC-DC buck converters for the CMS pixel project have been developed, based on the AMIS5 ASIC designed by CERN. The powering system of the Phase-1 pixel detector is described and the performance of the converter prototypes is detailed, including power efficiency, stability of the output voltage, shielding, and thermal management. Results from a test of the magnetic field tolerance of the DC-DC converters are reported. System tests with pixel modules using many components of the future pixel barrel system are summarized. Finally first impressions from a pre-series of 200 DC-DC converters are presented.

DC-DC conversion powering schemes for the CMS tracker at Super-LHC

The CMS experiment at the Large Hadron Collider (LHC) at CERN, Geneva, houses the largest silicon strip tracker ever built. For the foreseen luminosity upgrade of the LHC, the Super-LHC, however, a completely new silicon tracker will have to be constructed. One out of several major improvements currently under consideration is the implementation of a track trigger, with tracking information being provided to the first level trigger. Such an intelligent tracker design, utilising fast digital readout electronics, will most certainly lead to an increased power consump- tion, compared to todays tracker. In combination with the desire to reduce the amount of passive material inside the tracking volume and the impracticality to exchange or even add additional sup- ply cables, a novel powering scheme will be inevitable. In this article a powering scheme based on DC-DC conversion is proposed, and requirements for the DC-DC converters are discussed. Stud- ies of important DC-DC converter quantities such as the power efficiency, conducted and radiated noise levels, and material budget are presented, and a possible implementation of DC-DC buck converters into one proposed track trigger layout is sketched.

A DC-DC conversion powering scheme for the CMS Phase-1 pixel upgrade

The CMS pixel detector was designed for a nominal instantaneous LHC luminosity of 1⋅1034 cm−2s−1. During Phase-1 of the LHC upgrade, the instantaneous luminosity will be increased to about twice this value. To preserve the excellent performance of the pixel detector despite the increase in particle rates and track densities, the CMS Collaboration foresees the exchange of its pixel detector in the shutdown 2016/2017. The new pixel detector will be improved in many respects, and will comprise twice the number of readout channels. A powering scheme based on DC-DC conversion will be adopted, which will enable the provision of the required power with the present cable plant.The powering scheme of the CMS pixel detector will be described, and the performance of prototype DC-DC buck converters will be presented, including power efficiency, system tests with DC-DC converters and pixel modules, thermal management, reliability at low temperature, and studies of potential frequency locking between DC-DC converters.

Radiated electromagnetic emissions of DC-DC converters

For the CMS tracker at SLHC a new powering scheme is considered to be mandatory to allow the detector to provide at least the same performance as today at the LHC. The baseline solution of CMS foresees the use of DC-DC converters to provide larger currents with smaller losses. An important component of most converters are inductors which, however, tend to radiate the switching noise generated by the converter. The emissions of different inductors have been measured and simulated, the coil design has been optimized and noise susceptibility measurements, with present CMS hardware, have been performed. This article summarizes the results.

A DC-DC converter based powering scheme for the upgrade of the CMS pixel detector

Around 2016, the pixel detector of the CMS experiment will be upgraded. The amount of current that has to be provided to the front-end electronics is expected to increase by a factor of two. Since the space available for cables is limited, this would imply unacceptable power losses in the currently installed supply cables. Therefore it is foreseen to place DC-DC converters close to the front-end electronics, allowing the provision of power at higher voltages, thereby facilitating the supply of the required currents with the present cable plant. This conference report introduces the foreseen powering scheme of the pixel upgrade. For the first time, system tests have been conducted with pixel barrel sensor modules, radiation tolerant DC-DC converters and the full power supply chain of the pixel detector. In addition, studies of the stability of different powering schemes under various conditions are summarized. In particular the impact of large and fast load variations, which are related to the bunch structure of the LHC beam, has been studied.