Commissioning and First Performance of the Lhc Beam Instrumentation

This paper will outline the progress with LHC commissioning to date, detailing the performance achieved with all the main LHC beam instrumentation systems. It will include an overview of the beam loss system and its role in machine protection, along with that of the beam position system and its use for automatic orbit control. Results will be shown from the highly sensitive base band tune system as well as the bunch-bybunch and DC beam current transformer systems, the synchrotron light monitoring systems, the wire scanner system and OTR screens. INTRODUCTION The first beams circulated in the LHC on 10 September 2008 in full view of the world’s media. This was a resounding success, and was followed a few days later with RF captured beams circulating for several hours. Nine days on, a poor superconducting splice overheated during a hardware test at high current, creating an arc that pierced the helium containment vessel, with severe consequences. 14 months later, after a major magnet repair and consolidation programme, the LHC was once again cold and ready to take beam. Despite these efforts and the installation of a completely new Quench Protection System (QPS) its energy is currently limited to 3.5 TeV per beam. Further consolidation, requiring a long shutdown in 2012, will be necessary before it can run at its design energy of 7 TeV per beam. A one month run at the end of 2009 saw the LHC quickly advance with optics, collimation and working point studies at its 450 GeV injection energy. Ramp commissioning to 1.18 TeV followed, ending in collisions at 1.18 TeV per beam in all of its four main experiments. Further consolidation work was carried out on both the machine and experiments for the first two months of 2010, before the start of a 2 year run at the end of February. To date (late April 2010) the LHC is routinely ramping 2×10 protons to 3.5 TeV and colliding with a β* of 2 m in all four experiments. The emphasis now is on increasing the total intensity in the machine. This rapid progress with beam commissioning is in a large part down to the very good beam instrumentation with which the LHC is equipped. These systems and their contributions to this commissioning effort will be the subject of the remainder of this paper.