There was jubilation in the CERN Control Centre late in the afternoon on 12 November. Only a few hours before the annual winter shutdown of the accelerators, monitoring screens showed that a beam of lead ions dispatched from the SPS had reached the threshold of the LHC. For the first time the beam had been extracted close to the LHC along the TT60 transfer line. It marked another milestone towards the final target of circulating lead ions in the LHC to produce collisions.
Since the installation of the Low Energy Ion Ring (LEIR) in 2005, the team working on I-LHC, the project to deliver heavy ions to the LHC, has focused on the injector chain in order to supply ion beams to the LHC in optimal conditions. A year previously, ions that had been accumulated in LEIR and sent to the PS were ejected at the threshold of the SPS for the first time.
In 2007, ions were successfully injected into the SPS from the beginning of September. After many adjustments and studies, the beam had been accelerated with a view to its extraction into one of the two transfer lines linking the SPS and the LHC. But technical problems had arisen, including a vacuum leak detected in the PS at the beginning of November. By increasing ion losses, this leak had resulted in a reduction in the intensity of the ion beam, placing the success of the operation in jeopardy. However, at approximately 5.00 p.m. on 12 November, thanks to an increase in beam intensity to 20 million ions per bunch, the long-awaited beam finally made its appearance on the screens in the control room.
The next stage will be to refine and optimize the beam to reach the nominal intensity for the LHC of 100 million ions per bunch – this will be five times higher than that recently obtained.