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D. Froidevaux
consuming and eventually more space-consuming than planned. Whereas the
first two issues can, at least in principle, be solved with additional manpower and
increased costs, the space issue is a major one, which needs adequate planning
right from the start. The space issue has been compounded by the fact that the
muon system is traversed by the services of the other detectors, leading to issues
of ownership of space and to problems in collecting all the necessary information
for proper planning. This major complexity of the actual installation of the
services has been one of the major challenges of the Technical Coordination
team.
• Uniformity of technologies, power supplies and electronics. As already explained
in the introduction, the size of the muon project has necessitated the distribution
of the design and construction across different institutes and funding agencies.
This necessarily leads to a multitude of different choices for numerous components, from the choice of high-voltage power supplies to basic choices of
electronics (ASICs or FPGAs). A strong electronics coordination team is needed
to alleviate many of these pressures and lead to an overall system, which will be
much easier to maintain.
As for the other detector systems, the ATLAS collaboration has invested a
major effort into the validation of the muon spectrometer concept using highenergy test-beam muons. The ATLAS muon test-beam setup had both trigger and
tracking chambers placed in the appropriate geometrical positions and equipped
with alignment sensors. The most prominent goal (in 2004) was to test the ability
to monitor chamber movements and long-term deformations over time-scales of
several weeks with the required accuracy, a crucial ingredient for the ultimate
accuracy of muon measurements in the TeV range. The test-beam setup included
the calculation of deviations from the nominal chamber positions and the storage
of the results in a database. These constants were also directly determined by the
reconstruction program. The variation of the sagitta as reconstructed in the muon
beam, along with that measured from the optical alignment system, was studied
over a period covering the thermal fluctuations of a day–night cycle. The spread
of the difference between the two distributions was measured to be below 10 μm,
i.e. well within the specification of 30 μm. Finally, the correct performance of the
trigger was tested with the final trigger electronics prototypes and with all muon
systems taking data simultaneously at 40 MHz.
16.6 Trigger and Data Acquisition System
This section briefly describes the main design features and architecture of the
ATLAS trigger and data acquisition systems. A few examples of the overall trigger
performance expected in the actual configuration of the experiment are presented
in Sect. 16.8.4, where it is also compared to the expected performance of the CMS
trigger system.
D. Froidevaux
consuming and eventually more space-consuming than planned. Whereas the
first two issues can, at least in principle, be solved with additional manpower and
increased costs, the space issue is a major one, which needs adequate planning
right from the start. The space issue has been compounded by the fact that the
muon system is traversed by the services of the other detectors, leading to issues
of ownership of space and to problems in collecting all the necessary information
for proper planning. This major complexity of the actual installation of the
services has been one of the major challenges of the Technical Coordination
team.
• Uniformity of technologies, power supplies and electronics. As already explained
in the introduction, the size of the muon project has necessitated the distribution
of the design and construction across different institutes and funding agencies.
This necessarily leads to a multitude of different choices for numerous components, from the choice of high-voltage power supplies to basic choices of
electronics (ASICs or FPGAs). A strong electronics coordination team is needed
to alleviate many of these pressures and lead to an overall system, which will be
much easier to maintain.
As for the other detector systems, the ATLAS collaboration has invested a
major effort into the validation of the muon spectrometer concept using highenergy test-beam muons. The ATLAS muon test-beam setup had both trigger and
tracking chambers placed in the appropriate geometrical positions and equipped
with alignment sensors. The most prominent goal (in 2004) was to test the ability
to monitor chamber movements and long-term deformations over time-scales of
several weeks with the required accuracy, a crucial ingredient for the ultimate
accuracy of muon measurements in the TeV range. The test-beam setup included
the calculation of deviations from the nominal chamber positions and the storage
of the results in a database. These constants were also directly determined by the
reconstruction program. The variation of the sagitta as reconstructed in the muon
beam, along with that measured from the optical alignment system, was studied
over a period covering the thermal fluctuations of a day–night cycle. The spread
of the difference between the two distributions was measured to be below 10 μm,
i.e. well within the specification of 30 μm. Finally, the correct performance of the
trigger was tested with the final trigger electronics prototypes and with all muon
systems taking data simultaneously at 40 MHz.
16.6 Trigger and Data Acquisition System
This section briefly describes the main design features and architecture of the
ATLAS trigger and data acquisition systems. A few examples of the overall trigger
performance expected in the actual configuration of the experiment are presented
in Sect. 16.8.4, where it is also compared to the expected performance of the CMS
trigger system.