ATLAS detector assembly - the final steps

15 January 2008


The ATLAS detector

We are almost there with a complete and running detector, but before declaring victory a few important steps still have to be achieved. The next three months will be very critical; everything we left for the end has now to be installed, has to fit and has to become operational.

In the barrel we count four main activities:

  1. Some components of the inner detector have still to be signed off, after final service connections and final tests. In the first few weeks of January, the SCT heater system has to be finalized and brought to operation. Just after the 2 SCT end caps are fully cold tested, the pixel detector can be connected and debugged. All this will take about 3 months. The last step will be the installation of the external end flange, which will isolate environmentally the ID from the rest of ATLAS.
  2. Both calorimeters (LAr and Tile) have to finish the refurbishing of the front- end electronics in the barrel (on both sides). The two end caps are ready. On side C, once the warm exhaust pipe, which was damaged, is repaired, we will refill the vessel with Argon. All calorimeters should become fully operational by the end of March.
  3. The barrel muon spectrometer is just in the middle of its commissioning phase. Most of the lower sectors have to be fully debugged and connected to power. Here we are still waiting for a few cables to be delivered and then installed. The delivery of all power supplies is still on the critical path.
  4. In the last week of January the two small wheels, assembled on the surface in building 191, will travel to Point 1: once again two difficult transports and manipulations. On both sides we are preparing for their installation in situ, which should happen early February. To allow this, on both sides we are opening the detector, by moving the end-cap Toroids to their parking position. Side C is already done, side A will be opened in the next ten days. Once installed, the two small wheels will be promptly connected to their flexible service chains and immediately brought to operation.

All four activities will run in parallel. As soon as the ID and the Calorimeters are signed off, we will start the final closing of the detector. This should begin in the second half of March, first on one side. We are eager to close, because we still have to perform a final magnet test with all 4 magnets operational at full current (April-May). February will be the best month to take beautiful pictures of the detector, since it will be fully open.

Once we start closing, we will be able to move the muon big wheels into running position. There we still need to finish the final gas connections, install the tilt mechanism and perform the final alignment of the four wheels with respect to each other.

Just when the BW will be in their final position, we will be able to finish the installation of the EO large chambers (wheel fixed to the blue HO structure). Once this is done, the last section of the beam pipe, which includes the Lucid detector, will be installed and connected. The last step will then be the installation of the forward shielding.

While all this happens downstairs, on the surface we will be busy installing and bringing into operation the missing hardware of the initial Trigger and Data Acquisition systems. The main control room still needs some of its final functionality, both in hardware and software, as well as all satellite control rooms.

While we will alternate system debugging periods, overall milestone weeks, calibration periods and cosmics data taking, slowly we will start manning the control room, starting first with the infrastructure, safety and slow control desk. When the LHC machine will start commissioning beams we will have the entire control room operating 24h / day.

Barring any incident or unexpected calamity, the ATLAS detector should be fully installed, functional and tested in time and according to schedule. But let’s not count our chickens before they hatch …It will not be done until it’s all done!


Marzio Nessi