Speaker
Description
Summary
The CMS Tracker control system is used to configure and then operate the CMS
Tracker front-end electronics and readout system. The different component parts,
firmware and software are in various states of production and integration, and
QA/QC tests are taking place at all levels from that of the full control system
down to component level. This paper will review the ongoing activities on the key
parts and on the control system as a whole.
The off-detector front-end controller cards (optical mFEC) have been developed and
tested at CERN. 900 optical mFECs (plus spares) are foreseen for the whole of CMS,
since the same, or very similar, control system will also be used in the Pixel,
ECAL, Preshower and RPC detector systems. The mFEC can be used either on the 9U
FEC/CCS card or on a PCI carrier. A purely electrical version (i.e. without optical
transceiver, TRX) of the mFEC has also been designed for test-system applications
as well as a portable USB-interfaced FEC for rapid system debugging.
The FEC/CCS which hosts up to 8mFECs on a 9U board is approaching final production
with version 3. The Tracker requires 44 FEC/CCS out of a total 130 for all of CMS.
The card has been tested successfully in a VME 64x crate utilizing a bridge with a
LINUX PC running the XDAQ software. It has been fully populated with 8 mFECs, and
tests were carried out on the VME-local bus interface, fast timing path, as well as
monitoring of the temperature of the TRXs. The power consumption is 30W. 10 earlier
prototype FEC/CCS boards were made for use in system/beam tests and currently a pre-
production of 10 boards is ongoing.
The production of optical control links components is almost complete. The yield is
very high indeed. All parts have been tested either at the manufacturer or by CERN
to ensure the reliability of the front-end digital optohybrid (DOH) and off-
detector TRX parts, as well as the fibres and connectors. Only known-good parts are
being used for assembly and integration into the final system. Component
obsolescence in the very dynamic telecom/datacoms industries is also a serious
concern and a suitably conservative approach to spares has been adopted. The DOHs
are now being integrated into the Tracker sub-systems, where the different sub-
systems have developed their own DOH modules (DOHM), that also include solutions
for fibre-management.
The communication and control unit ASICs (CCUs), have been available in a final
form for some time already, along with modules (CCUMs) to house them. A test-system
was built at CERN, allowing for a full control ring with redundancy, to be tested
exhaustively with up to 16 CCUMs in the ring. The test system is fully configurable
such that the number of CCUMs can be adjusted, as well as the associated cable
lengths, and the eventual failure of any given CCUM, or associated element can be
simulated and studied.
On the software front, the controls software consists of several dedicated layers
of code. The first layer is able to access the VME through the PCI to VME
interface. The original software in this layer was intended as a Linux device
driver able to drive either an electrical and optical PCI FEC. The second layer
manages the control ring and the way in which the the front-end ASICs are accessed
and configured through the I2C bus. A third layer manages the eight rings on a
single FEC/CCS board and the fourth layer is the high level software that will be
integrated in the complete framework of the data acquisition system in the CMS
experiment using XDAQ. The high level software is able to retrieve information from
a database management system to configure the front-end ASICs with the appropriate
settings. It also manages the handling of possible errors in the ring, switching
between the primary and backup control path in the redundancy scheme. The speed at
which the system commands are transmitted has been measured in detail and this will
be reported.
The control system for the Tracker Outer Barrel (TOB) will be considered in more
detail as an example application. The integration and assembly and testing of the
various parts onto ‘rods’ (the basic detector unit of the TOB) has been defined and
the activity is currently well under way. No rods have been rejected due to
failures in the control elements so far. A thorough test of the TOB control system
using final CCU and DOH carrier boards is also under way, employing the latest
versions of the controls software. The performance of the control system with up to
10 TOB-variant CCUMs in the ring has been studied, with the front-end parts exposed
to temperatures between ambient room temperature and -30C, which is below the
intended operating temperature of the Tracker. The control system works well, with
a low rate of transaction errors (at room temperature and at low temperature), in
tests conducted continuously over several days with I2C commands sent to the
various front-end components in a continuous stream. More tests at different
temperatures are foreseen and these will be reported.
