Speaker
Description
Summary
Performance of the CMS detector of the Large Hadron Collider (LHC) is affected by
the position and orientation of the individual detectors. Therefore, the CMS
detector has an alignment system that consists of several subsystems. One of them
is the barrel and end-cap internal alignment, which measures the positions of the
muon detectors with respect to the linking points. This system will consist of LED
light-sources with related electronics, video cameras equipped with video-sensors,
temperature and tilt meters and a local network of 36 pcs PC-104 based computer for
data acquisition and system control.
The optical, opto-electronic components and the computers have to work in a 2 Tesla
strong magnetic environment. The possible damages induced by the strong magnetic
field can alter electrical and optical characteristics of the components and thus
the accuracy of the whole alignment system. In late 2004 the CMS Collaboration
decided to put up a special experiment for the CMS Muon System with the Alignment
components mounted, in order to enable the characterisation of the whole system
under real conditions. For the experiment only the most crucial parts of the
detector system (Sector 10/11 from each Wheel) will be installed, equipped and
tested.
As it was reported in our earlier papers a computer network - based on dedicated so
called mini-Crates - will be used for controlling of the opto-electronic
components of the Alignment System. The delayed delivery of the mini-Crates prevents
them to be used in the scheduled magnetic run. Their functionality can be replaced
by the PIConNET micro-controller board, which is a versatile board equipped with an
Ethernet communication interface.
For communication media we have chosen twisted pair Ethernet and for communication
protocol we use a User Datagram Protocol (UDP) based proprietary protocol. The
advantages of Ethernet and UDP/IP technologies are clear: they are mature and well
tested, many applications are available for development and debugging, they are
scalable and cost efficient.
The dynamic discovery of components (clients, masters and servers) is a key function
of the design. For this purpose we designed and implemented a custom protocol, which
is similar to the Dynamic Host Configuration Protocol (DHCP).
Our contribution will show the design of the dedicated PIConNET based distributed
system for magnetic test of the CMS Muon Barrel Alignment. The investigation is
focused on the components that are very sensitive for the magnetic field and on
those methods that preferably have to be applied in case of trouble.
