News from the pit

17 March 2008

Copper pipes feed vital gases into the muon subdetectors

Tubes run across and into the ATLAS detector like very neat strings of spaghetti, bringing gases to the muon subdetectors. This is the muon “plumbing system”, and although it is unlikely to grab the news headlines, it is an essential component of the detector – and it is nearing completion.

The pipes take a mixture of carbon dioxide and pentane from the surface to each subdetector. “The primary gas distribution is on the surface,” says Jan Godlewski of CERN, ATLAS fluids coordinator. “Then pipes that were installed several years ago send the gases to the secondary distribution room in USA15.” From there, the gases are sent to the detector itself, and that’s where Jan’s team has been working.

“I would say altogether we have put down around 200 km of pipes,” Jan says. “Some of those pipes are 50 metres long without a connection – it was tricky work snaking them around inside the detector.” Jan describes himself as the ATLAS Polish plumber, in reference to a recent controversy in France about Polish plumbers coming to work on the French territory.

But the muon gas system is more than a simple plumbing system – a sophisticated control system ensures that the correct amount of gas is sent to each subdetector. “The gas system can’t work without the control,” says Jan. “So on top of making all the pipe connections we also have to connect all the control cables.”

The simplest control system would be powered by electricity, but the strong magnetic fields in the detector would provide too much interference and demanded another solution. “We have used pneumatic control instead,” says Jan. “Some of the pneumatic lines are more than 100 metres long, so then you have a problem with reaction times – it’s much slower. But there was no choice.”

Control and commissioning work has been performed by the Gas Group in collaboration with the muon community, says Jan, and the cabling work has been done by the Technical Coordination cabling team led by Sergei Malyukov of the Joint Institute for Nuclear Research in Dubna, working with an outside company.

“The barrel part of the work was finished around a year ago and now we’re finishing the Big and Small Wheels,” he says. Work on the Big Wheels on Side A was completely connected ten days ago. Last week, Jan’s team finished working on the Big Wheels on Side C too. “By this Tuesday, work on the Small Wheel faces should be done too, because they want to put the end cap toroid back in position,” says Jan.

One more huge task to be crossed-off the commissioning to-do list!

Colin Barras



Colin Barras