TOTEM Construction Complete

The winter technical stop saw the final steps of the installation of the TOTEM experiment. After 8 years of development, the inelastic telescope T1 was successfully installed inside CMS at both sides of the interaction point. This detector joins the previously installed inelastic telescope T2 and the Roman Pots (147m and 220m from the CMS interaction point) to study both elastic and inelastic proton scattering.


The Genova team who designed and built the detector in front of the '+' arm of the T1 telescope after final insertion. All the detector chambers were assembled at the Petersburg Nuclear Physics Institute, Gatchina, Russia. Major contributions to the construction of the support structure and the installation process came from CERN.

“Installing the T1 detector was an important milestone for TOTEM,” says Joachim Baechler, Technical Coordinator for TOTEM. Enrico Robutti from Genova, responsible for the T1 project, added: "The T1 detector was carefully installed into the end-caps of the CMS experiment over the technical stop – a delicate operation that required the CMS detector to be opened. After the successful installation, we have now begun taking calibration data in preparation for the special runs during 2011/12."

Also the Roman Pot project has now been completed with the installation of 12 additional detector packages at a distance of 147m from the interaction point. "This was an extremely delicate operation as, during data taking, the sensors in these installations will approach the LHC beam centre within a few millimeters, and therefore their alignment has to be precise on the level of better than 100 microns. All services have been installed and tested and the detectors are now running to our satisfaction," says Gennaro Ruggiero, the Roman Pot project leader.

Installation of one of the T1 support trusses inside the CMS endcap ('–' side).

The two half-arms under test on the installation platform, before insertion ('+' side).

The particle detectors T1 together with the previously installed T2 surround the LHC pipe, providing a 360 view of the charged particles emerging from pp collisions with a greatly enhanced coverage in the forward directions. While the team had been able to measure proton scattering with the previous installation, the addition of T1 completes the TOTEM experiment. The completion will allow TOTEM to take precise measurements of the proton-proton interaction cross-sections, as well as detailed studies of elastic and diffractive pp scattering. For this, TOTEM has to use dedicated runs at low luminosities with a reduced pile-up of events, but also to allow the Roman Pot detectors to approach the beam to the smallest possible distances.

The TOTEM collaboration expects an exciting year in 2011.

by Katarina Anthony