Speaker
Dr.
Lars Eklund
(University of Glasgow)
Description
The upgrade of the LHCb experiment, planned for 2018, will transform
the experiment to a trigger-less system reading out the full detector
at 40 MHz event rate. All data reduction algorithms will be executed
in a high-level software farm with access to the complete event
information. This will enable the detector to run at luminosities of
2 x 10^33 /cm^2/s and probe physics beyond the Standard Model in the
heavy flavour sector with unprecedented precision.
The Vertex Locator (VELO) is surrounding the interaction region is
used to reconstruct primary and secondary vertices and measure the
flight distance of long-lived particles. The upgraded VELO must be
capable of fast pattern recognition and track reconstruction while
maintaining the exceptional resolution of the current detector. This
is realised through a hybrid pixel detector using silicon sensors with
55x55 um^2 pitch, read out by the VeloPix ASIC which is being
developed based on the TimePix/MediPix family. The hottest region will
have pixel hit rates of 900 Mhits/s yielding a total data rate more
than 3 Tbit/s for the upgraded VELO.
The detector modules are located in a separate vacuum, separated from
the beam vacuum by a thin custom made foil. The foil will be
manufactured through milling and possibly thinned further by chemical
etching. The detector halves are retracted when the beams are injected
and closed at stable beams, positioning the first sensitive pixel at
5.1 mm from the beams. The high data rates require development of
low-mass, high-speed, flexible electrical serial links bringing the
data out of the vacuum where electrical-to-optical conversion is
performed.
The material budget will be minimised by the use of evaporative CO_2
coolant circulating in microchannels within 400 um thick silicon
substrates. Microchannel cooling brings many advantages: very
efficient heat transfer with almost no temperature gradients across
the module, no CTE mismatch with silicon components, and low material
contribution. This is a breakthrough technology being developed for
LHCb.
The 40 MHz readout will also bring significant conceptual changes to
the way in which the upgrade trigger is operated. Work is in progress
to incorporate momentum and impact parameter information into the
trigger at the earliest possible stage, using the fast pattern
recognition capabilities of the upgraded detector. The current status
of the VELO upgrade will be described together with a presentation of
recent test results.
Primary author
Dr.
Lars Eklund
(University of Glasgow)