The Large Hadron Collider (LHC) runs a hundred meters below ground for experimental research in the field of high energy physics. The collider operates a pair of counter-rotating particle rings which have crossovers at four experiment sites. There particles crash from opposite directions into each other and create the signatures that indicate the presence of short lived particles. To prove this, the generated data must be recorded reliably. Monitoring of the LHC for correct operation is accomplished through the Open Analogue Signal Information System, called OASIS. It picks up relevant monitoring signals from various places to make sure that the system is operating as intended.
The OASIS system uses a set of digitisers to acquire the signals and send them to users via Ethernet. The digitisers however are very expensive and there cannot be one distinct digitiser for every signal to be monitored. A switching system is used to allow OASIS to select, which signals to show from the variety of available signals. Historically this switching system has been based on VXI and more recently on cPCI systems.
A new switching system for OASIS
Within the frame of a biennial system upgrade CERN has closed down the collider as of February 2013 to upgrade all systems – including OASIS. At each of the four experiment sites up to 16 signals, selected from 104 sensors, have to be made available for digitizing.
The analogue signals have frequency content to many MHz and there is potential for considerable differences in level from the various monitoring positions. This puts challenging constraints on the required bandwidth and the allowable crosstalk between channels. If signals from high level sources and signals from low level sources are required at the same time on different channels, the high level signals could disturb the low level signals. Remote control is another essential requirement for the switching system.
So a switching matrix with a size of 104x16 was required,