Speaker
Description
Summary
There is a clear need for a new system of power delivery to the upgraded Atlas Silicon Tracker for the SLHC. Conventional powering will result in an efficiency of power delivery to the detector of about 10% with existing cables whose size are already limited in cross section due to space and mass constraints. A system featuring DC-DC converters with voltage ratios of ten will result in an estimated efficiency on the order of 80% with existing cables.
One approach to DC-DC conversion utilizes the buck regulator architecture. As DC-DC buck converters are commonly used in the commercial market, we have been surveying and testing current available devices to understand the current state of the art. Additionally we are investigating industry trends to determine if a commercial solution with our unique requirements might be forthcoming.
Foremost of our unique requirements is operation in a high magnetic field. This necessitates the use of an air core inductor, which implies the need for high switching frequencies that lie in the readout ASIC’s bandwidth. Additional noise introduced by the converter is thus one of the primary concerns. The radiation hardness of the devices, and the relatively high voltage ratios needed are also of primary concern.
Over the past year we have tested a number of devices that, although they lack the high voltage ratios required, have enabled us to learn a number of lessons. For example, the one device that we irradiated with gammas up to 100 Mrad showed no change in performance. Also, we have conducted noise tests with our own custom module utilizing current Atlas ABCD ASICs connected to a large silicon strip detector and mounted with a daughter buck regulator board. We found no noise increase due to switching noise on the power and ground. Magnetic/electrical pickup on the 8 cm silicon strips from the air-core inductor required shielding to reduce the noise to a satisfactory level.
Market forces are now driving the development of a new generation of converters with ratios greater than 10. We will shortly be testing such promising devices for their radiation hardness, efficiencies and noise performance. Additionally, we have fabricated several small micro-H inductors that show promise in their initial testing. Results of the testing of the new devices will be presented.
