Speaker
Description
Summary (Additional text describing your work. Can be pasted here or give an URL to a PDF document):
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 talk, 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.
The buck converter is the simplest inductor-based stepdown
converter. With relatively few components and the ability
to deliver currents of several Amperes at efficiencies of 70-80 %,
even for high conversion ratios, this DC-DC converter type is
currently the best candidate for use in the CMS tracker. However,
several challenges exist on the system level and must be
adressed: switching with frequencies in the MHz range might
inject conductive noise into the detector system; air-core inductors,
needed because of saturation of ferrite cores in the 3.8 T
magnetic field of CMS, might radiate electro-magnetic noise;
the converter’s size and mass must be reduced as much as possible,
without degrading its electrical performance. A low efficiency
would cancel out the advantages of DC-DC conversion.
DC-DC buck converters based on a commercial, not
radiation-hard chip, and small, light-weight air-core toroids
have been developed. The noise performance has been studied
extensively in system tests. In combination with pi-filters,
which lead to an efficiency loss below 1% , the boards can be
operated across the whole allowed input voltage range without
adding extra noise to the test system. The material budget of
the AC2 converters amounts to 10% of the material of a current
strip module. Due to savings in cables and motherboards, about
8% of material could be saved by using such converters (for an
efficiency of 80% and a conversion ratio of eight). Plans exist to
use buck converters for the pixel detector already in phase-1 and
in the outer tracker during phase-2. These studies will therefore
be continued using custom radiation-hard converter ASICs.
