Speaker
Description
Summary
The Run-II Upgrade of the Tevatron increased the center-of-mass energy from 1.8
to 1.96 TeV as well as the luminosity. The goal for Run-II is now around 8
fb-1. To take advantage of this, a larger Silicon detector was designed. The
SVX-II increases the coverage of the interaction region by a factor of two and
adds the capability of having 3D hits. It consists of six bulkheads, each one
consists of 12 wedges. Each wedge consists of 5 layers of double-sided silicon.
To increase the impact parameter resolution, the L00 was added. It is mounted
on the beam pipe inside of the SVX-II. It consist of radiation hard single
sided silicon and has 48 ladders altogether. The ISL extends
coverage in eta and adds additional tracking points as a link between SVX-II
tracks and the Central Outer Tracker. The ISL consists 296 double-sided ladders
arranged in three barrels, the two forward barrels having two layers, the
central barrel having only one.
The readout chips and the DAQ are common for all detectors. The central
component of the readout is the radiation hard 128 channel SVX3D chip. It
consists of an analog frontend with a 46 capacitor cell deep pipeline which
samples the data every 132 ns and a digital backend containing ADCs. The clear
separation of the two parts allows the deadtimeless operation of the chip. Five
ladders are connected to one Portcard, which serves as an interface between the
ladder and the DAQ/power supply side. It distributes the DAQ commands to all
attached ladders,as well as low and high voltage. It also converts the data
from the chip into an optical signal, which is feed into the VME based DAQ.
The cooling and power supply interlock systems are as well shared between all
three subdetectors.
Commissioning off the whole system started in 2001 and it took significant
effort to become operational. Problems encountered included:
-Complications during the installation
-A lack of testing for the cooling system under operational conditions. The
blocked ISL cooling lines remained undetected. Clearing them
was a challenging task.
-The common-mode noise in L00 severely affected its performance.
-The optical readout system turned out to be very sensitive in matching
transceivers and receivers.
These problems have been addressed Currently 92% of the ladders are
powered and 84 % deliver data without errors. During operation some new failure
modes were found and studied.
-Loss of wire bonds due to Lorentz forces on the wire bonds. Synchronous trigger
conditions resonated the wire bonds, which lead to failure.
This has been mitigated by a dedicated resonance detection system.
-Beam incidents damaging the chip.
-Single event upsets in the power supplies and DAQ boards in
the collision hall.
The silicon sensors are operated at a S/N of about 11-15 depending on the
ladder type. With this high S/N, the single hit efficiency is
above 99 %. As luminosity increases, a continuous effort is taking place to
make Silicon readout as fast as possible. A concern for longevity is the
amount of radiation damage to the system. With the current luminosity
prospects for Run-II, the damage to the sensors is the prime concern and a
continuous effort takes place to measure the radiation damage the system has
already accumulated.
